Medtronic 7304 Reference Guide

INSYNC MAXIMO

Dual chamber implantable cardioverter defibrillator with cardiac resynchronization therapy including sequential biventricular pacing

™

7304

Reference Manual

Caution: Federal Law (USA) restricts this device to sale by or on the order of a physician (or properly licensed practitioner).

INSYNC MAXIMO

™

7304

Reference Manual

A guide to the operation and programming of the Model 7304 InSync Maximo dual chamber implantable cardioverter defibrillator with cardiac resynchronization therapy

The following are trademarks of Medtronic:

Active Can, Cardiac Compass, Checklist, Decision Channel, Flashback, InSync, InSync II Marquis, InSync Sentry, InSync Maximo, Leadless, Marker Channel, Marquis, Maximo, Medtronic, Medtronic CareLink, PR Logic, Patient Alert, Quick Look, QuickLink, T-Shock

Contents

Introduction 11

Part I Quick overview 13

1 Quick reference 15

1.1 Physical characteristics 16

1.2 Magnet application 18

1.3 Projected longevity 18

1.4 Replacement indicators 20

1.5 Typical charge times 21

1.6 High-voltage therapy energy 21

1.7 Stored data and diagnostics 22

1.8 New and enhanced features 24

2 The InSync Maximo system 25

2.1 System overview 26

2.2 Indications and usage 29

2.3 Contraindications 30

2.4 Patient screening 30

3 Emergency therapy 31

3.1 Delivering emergency therapies 32

3.2 Delivering an emergency defibrillation therapy 33

3.3 Delivering an emergency cardioversion therapy 34

3.4 Delivering emergency fixed burst pacing 34

3.5 Enabling emergency VVI pacing 35

Part II Device implant and patient follow-up

procedures 37

4 Implanting the device 39

4.1 Overview 40

4.2 Preparing for an implant 40

4.3 Replacing a device 42

4.4 Surgical approach 43

INSYNC MAXIMO™7304 Reference Manual

Contents

4.5 Sensing and pacing measurements 47

4.6 Connecting the leads to the device 47

4.7 Testing defibrillation operation and effectiveness 51

4.8 Positioning and securing the device 54

4.9 Completing the implant procedure 54

5 Conducting a patient follow-up session 57

5.1 Patient follow-up guidelines 58

5.2 Verifying the status of the implanted system 59

5.3 Verifying effective cardiac resynchronization therapy 59

5.4 Verifying effective basic pacing 60

5.5 Verifying accurate detection and appropriate therapy for ventricular tachyarrhythmias 62

Part III Configuring the device for the patient 65

6 Detecting tachyarrhythmias 67

6.1 Detection overview 68

6.2 Setting up sensing 71

6.3 Detecting VF episodes 76

6.4 Detecting VT episodes 79

6.5 Detecting FVT episodes 85

6.6 Detecting tachyarrhythmia episodes with Combined Count 90

6.7 Monitoring episodes for termination or redetection 92

6.8 Enhancing detection with PR Logic criteria 96

6.9 Enhancing VT detection with the Stability criterion 104

6.10 Detecting double tachycardias 106

6.11 Detecting prolonged tachyarrhythmias with High Rate Timeout 107

7 Treating tachyarrhythmia episodes 111

7.1 Treating VF with defibrillation 112

7.2 Treating VT and FVT with antitachycardia pacing 121

7.3 Treating VT and FVT with cardioversion 131

INSYNC MAXIMO™7304 Reference Manual

Contents

7.4 Optimizing therapy with Smart Mode and Progressive Episode Therapies 139

8 Treating ventricular dysynchrony and

bradycardia 145

8.1 Providing basic pacing therapy 146

8.2 Dual chamber pacing 154

8.3 Single chamber pacing 165

8.4 Promoting continuous CRT delivery 169

8.5 Rate adjustments to optimize cardiac output 179

8.6 Managing atrial tracking to optimize A-V synchrony 191

8.7 Providing Ventricular Safety Pacing 204

9 Optimizing charge time and device longevity 209

9.1 Optimizing charge time 210

9.2 Optimizing device longevity 212

Part IV Evaluating and managing patient treatment 215

10 Using the programmer 217

10.1 Setting up and using the programmer 218

10.2 Display screen features 219

10.3 Viewing and programming device parameters 224

10.4 Starting and ending patient sessions 229

10.5 Viewing live waveform traces 231

10.6 Recording live waveform strips 238

10.7 Saving and retrieving device data 240

10.8 Printing reports 244

11 Using system evaluation tools 251

11.1 A summary of system evaluation tools 252

11.2 Taking a quick look at device activity 253

11.3 Using the Patient Alert feature 254

11.4 Streamlining follow-ups with Checklist 262

12 Setting up and viewing collected data 267

12.1 A summary of data collection 268

12.2 Viewing battery and lead status data 269

12.3 Printing rate histograms 274

INSYNC MAXIMO™7304 Reference Manual

Contents

12.4 Viewing the Heart Failure Management report 278

12.5 Viewing clinical trends in the Cardiac Compass report 282

12.6 Viewing the episode and therapy efficacy counters 288

12.7 Viewing episode data 291

12.8 Viewing Flashback Memory 301

12.9 Setting up data collection 302

12.10 Viewing and entering patient information 308

12.11 Automatic device status monitoring 311

13 Testing the system 315

13.1 Testing overview 316

13.2 Evaluating the underlying rhythm 316

13.3 Measuring pacing thresholds 317

13.4 Measuring lead impedance 320

13.5 Measuring EGM amplitude 322

13.6 Testing the device capacitors 324

14 Conducting Electrophysiologic Studies 327

14.1 EP Study overview 328

14.2 Inducing VF with T-Shock 329

14.3 Inducing VF with 50 Hz Burst 333

14.4 Inducing an arrhythmia with Manual Burst 335

14.5 Inducing an arrhythmia with PES 338

14.6 Delivering a manual therapy 340

15 Solving system problems 345

15.1 Overview 346

15.2 Solving cardiac resynchronization therapy problems 346

15.3 Solving sensing problems 347

15.4 Solving tachyarrhythmia detection problems 349

15.5 Solving tachyarrhythmia therapy problems 350

15.6 Solving bradycardia pacing problems 351

15.7 Responding to device status indicators 352

INSYNC MAXIMO™7304 Reference Manual

Appendices 355

A Warnings and precautions 357

A.1 General warnings 358

A.2 Handling and storage instructions 358

A.3 Resterilization 359

A.4 Device operation 360

A.5 Lead evaluation and lead connection 361

A.6 Follow-up testing 363

A.7 Explant and disposal 363

A.8 Medical therapy hazards 364

A.9 Home and occupational environments 366

B Device parameters 369

B.1 Emergency settings 370

B.2 Detection parameters 371

B.3 Therapy parameters 372

B.4 Pacing parameters 375

B.5 System maintenance parameters 378

B.6 Data collection parameters 380

B.7 System test and EP study parameters 381

B.8 Fixed parameters 384

B.9 Patient information parameters 385

B.10 Programmer symbols 386

B.11 Parameter interlocks 388

C Device programming recommendations 389

C.1 Device programming recommendations 390

C.2 V-V Delay programming recommendations 392

Contents

Glossary 397

Index 407

INSYNC MAXIMO™7304 Reference Manual

Introduction

Using this manual

Before implanting the device, it is strongly recommended that you:

Manual conventions

Throughout this document, the word “device” refers to the implanted InSync Maximo device.

Introduction

Refer to the product literature packaged with the device for

•

information about prescribing the device.

Thoroughly read this manual and the technical manuals for

•

the leads and the implant tools used with the device.

Discuss the procedure and the device system with the

•

patient and any other interested parties, and provide them with any patient information packaged with the device.

Technical support

The nominal value for that parameter.

On-screen buttons are shown with the name of the button surrounded by brackets: [Button Name].

Medtronic employs highly trained representatives and engineers located throughout the world to serve you and, upon request, to provide training to qualified hospital personnel in the use of Medtronic products.

In addition, Medtronic maintains a professional staff of consultants to provide technical consultation to product users. For medical consultation, Medtronic can often refer product users to outside medical consultants with appropriate expertise.

For more information, contact your local Medtronic representative, or call or write Medtronic at the appropriate address or telephone number listed on the back cover.

symbol in parameter tables indicates the Medtronic

INSYNC MAXIMO™7304 Reference Manual

Introduction

References

Notice

The primary reference for background information is Zacouto FI, Guize LJ. Fundamentals of Orthorhythmic Pacing. In: Luderitz B,

Cardiac Pacing Diagnostic and Therapeutic Tools.

ed. Springer-Verlag; 1976: 212-218.

See these additional references for more background information:

Estes M, Manolis AS, Wang P, Eds.

•

Cardioverter-Defibrillators

Inc. 1994.

Kroll MW, Lehmann MH, Eds.

•

Cardioverter-Defibrillator Therapy: The Engineering-Clinical Interface

Singer I, Ed.

•

NY: Futura Publishing Co. 1994.

Singer I, Barold SS, Camm AJ, Eds.

•

Therapy of Arrhythmias for the 21st Century: The State of the Art

. Norwell, MA: Kluwer Academic Publishers 1996.

Implantable Cardioverter-Defibrillator

. Armonk, NY: Futura Publishing Co. 1998.

. New York, NY: Marcel Dekker,

Implantable

Nonpharmacological

New York:

. Armonk,

This software is provided as an informational tool for the end user. The user is responsible for accurate input of patient information into the software. Medtronic makes no representation as to the accuracy or completeness of the data input into the software. Medtronic SHALL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES TO ANY THIRD PARTY WHICH RESULTS FROM THE USE OF THE INFORMATION PROVIDED IN THE SOFTWARE.

INSYNC MAXIMO™7304 Reference Manual

Quick overview

Part I

1Quick reference

1.1 Physical characteristics 16

1.2 Magnet application 18

1.3 Projected longevity 18

1.4 Replacement indicators 20

1.5 Typical charge times 21

1.6 High-voltage therapy energy 21

1.7 Stored data and diagnostics 22

1.8 New and enhanced features 24

Chapter 1

Physical characteristics

1.1 Physical characteristics

Table 1-1. Device physical characteristics

Volume

Mass

H x W x D

Surface area of device

40 cm

78 g

73 mm x 51 mm x 15 mm

67 cm

3 b

can

Radiopaque ID

Materials in contact with human tissue

PRL

Titanium / polyurethane /silicone rubber / silicone adhesive

Battery Lithium silver vanadium oxide

Connectors Two IS-1 connectors for pacing and

sensing, one IS-1 connector for pacing, two DF-1 connectors for high-voltage therapy, Active Can electrode (programmable)

Measurements are nominal values based on CAD (computer aided design) model measurements and are rounded to the nearest unit.

Volume with connector holes unplugged.

Grommets may protrude slightly beyond the can surface.

Engineering series number follows the radiopaque code.

These materials have been successfully tested and verified for biocompatibility. The device does not produce an injurious temperature in the surrounding tissue.

Table 1-2. Lead connections

Device port Connector type Software name

SVC (HVX) DF-1 SVC

RV (HVB) DF-1 RVcoil

Can

RV IS-1 bipolar RVtip and RVring

INSYNC MAXIMO™7304 Reference Manual

—

Can

1Quick reference

Physical characteristics

Table 1-2. Lead connections (continued)

Device port Connector type Software name

LV IS-1 bipolar LVtip and LVring

A IS-1 bipolar Atip and Aring

Figure 1-1. Lead connections

1 SVC (HVX) 2 RV (HVB) 3 Can (HVA) 4 LV 5 RV 6 A

Figure 1-2. Suture holes

INSYNC MAXIMO™7304 Reference Manual

Chapter 1

Magnet application

1.2 Magnet application

Bringing a magnet close to the device triggers changes in device operation as shown in Table 1-3. When the magnet is removed, the device returns to its programmed operations.

For information on demonstrating Patient Alert tones to the patient, see Section 11.3.4, “Instructing the patient”, page 260.

Table 1-3. Effects of magnet application on the device

Pacing mode as programmed

Pacing rate and interval as programmed

VF, VT, and FVT detection suspended

Patient Alert audible tones (20 s or less)

high/low dual tone (high urgency

•

alert occurred) on/off intermittent tone (lower

•

urgency alert occurred) continuous test tone (no alert

•

occurred) no tone (alerts are disabled)

•

Rate response adjustments are suspended while a Patient Alert tone sounds.

Detection resumes if telemetry is established and the application software is running, or detection resumes after the application software has started.

Or “VF Detection/Therapy Off” is the only alert enabled.

1.3 Projected longevity

Longevity estimates are based on accelerated battery discharge data and device modeling with EGM pre-storage off (see Table 1-4).

INSYNC MAXIMO™7304 Reference Manual

1Quick reference

Projected longevity

Table 1-4. Projected longevity in years with pacing outputs programmed to the specified amplitude and 0.4 ms pulse width, DDD mode, 100% biventricular pacing, specified percentage of atrial pacing at 60 ppm with the remainder at 70 bpm atrial tracking, semi-annual full-energy charges.

Amplitudes: A/RV; LV

2.5 V; 3.0 V

3.0 V; 4.0 V

% atrial pacing

0% 5.8 6.2 6.5

25% 5.6 6.1 6.4

50%

100% 5.2 5.8 6.1

0% 5.0

25% 4.8 5.3

50% 4.6 5.2 5.6

100% 4.4 5.0 5.4

Semi-annual full-energy charges may include therapy shocks or capacitor formations. Additional full-energy charges due to therapy shocks, device testing, or capacitor formation reduces device longevity by approximately 23 days (0.06 years). Additional 30 J charges due to therapy shocks or device testing reduces device longevity by approximately 21 days (0.06 years).

500 Ù pacing impedance

5.5

700 Ù pacing impedance

6.0 6.3

5.5

900 Ù pacing impedance

5.8

5.7

The longevity of the ICD is dependent on several factors. The following factors result in decreased longevity:

An increase in pacing rate, pacing amplitude or pulse

•

width; the ratio of paced to sensed events; or the charging frequency

A decrease in pacing impedance

•

Using the pre-onset EGM storage feature or Holter telemetry

•

Considerations for using EGM pre-storage – When the EGM pre-storage feature is programmed Off, the device starts to store EGM following the third tachyarrhythmia event and also provides up to 20 s of information before the onset of the tachyarrhythmia, including:

AA and VV intervals

•

Marker Channel

•

Interval Plot Flashback

•

INSYNC MAXIMO™7304 Reference Manual

Chapter 1

Replacement indicators

When the EGM pre-storage feature is programmed On, the device also collects up to 20 s of EGM information before the onset of the arrhythmia.

In a patient who uniformly repeats the same onset mechanisms, the greatest clinical benefit of pre-onset EGM storage is achieved after a few episodes are captured. To maximize the effectiveness of the EGM pre-storage feature and optimize device longevity, consider these programming options:

•

Turn pre-storage On to capture possible changes in the onset mechanism following significant clinical adjustments, for example, device implant, medication changes, and surgical procedures.

Turn pre-storage Off once you have successfully captured the information of interest.

1.4 Replacement indicators

Battery voltage and messages about replacement status appear on the programmer display and on printed reports. Table 1-5 lists the Elective Replacement Indicator (ERI) and the End of Life (EOL) conditions.

Table 1-5. Replacement indicators

Elective Replacement (ERI) ≤ 2.62 V

End of Life (EOL) 3 months after ERI

ERI date – The Quick Look and Battery and Lead Measurements screens display the date when the battery reached ERI.

Temporary voltage decrease – The battery voltage temporarily decreases following a high-voltage charge. If a battery measurement is taken immediately after a high-voltage charge, the ERI or EOL indicator may be displayed. However, this is a temporary status that will return to normal when the battery has recovered from the charge.

EOL indication – If the programmer indicates that the device is at EOL, replace the device immediately.

INSYNC MAXIMO™7304 Reference Manual

Post-ERI conditions – EOL device status is defined as 3 months following an ERI indication assuming the following post-ERI conditions: 0% DDD atrial pacing, 100% DDD RV and LV pacing at 60 ppm, 3 V atrial and RV pacing amplitude, 4 V LV pacing amplitude, 0.4 ms pulse width; 500 Ù pacing load; and six 35 J charges. EOL may be indicated before the end of 3 months if the device exceeds these conditions.

1.5 Typical charge times

The most recent capacitor charge time appears on the programmer display and on printed reports and can be evaluated using the Charge/Dump test (see Table 1-6).

Table 1-6. Typicalafull-energy charge times

At Beginning of Life (BOL)

At Elective Replacement (ERI)

These charge times are typical when the capacitors are fully formed.

7.1 s

9.0 s

1Quick reference

Typical charge times

1.6 High-voltage therapy energy

The stored energy of the device is derived from the peak capacitor voltage and is always greater than the energy delivered by the device. Table 1-7 compares the programmed energy levels delivered by the device to the energy levels stored in the capacitors before delivery.

Table 1-7. Comparison of delivered (programmed) and stored energy levels

Energy ( J)

Delivereda/ Programmed Stored

35 39 7.1

32 37 6.5

30 34 6.1

28 32

26 30 5.2

25 29 5.0

24 27 4.8

22 25 4.4

Charge Timec( s)

5.7

Delivereda/ Programmed Stored

Energy ( J)

10 12 2.0

9 10.5 1.8

8 9.3 1.6

6 7.1 1.2

4 4.8 0.8

3 3.6 0.6

INSYNC MAXIMO™7304 Reference Manual

8.2 1.4

5.9 1.0

Charge Timec( s)

Chapter 1

Stored data and diagnostics

Table 1-7. Comparison of delivered (programmed) and stored energy levels (continued)

Energy ( J)

Delivereda/ Programmed Stored

20 23 4.0

18 21 3.6

16 19 3.2

15 17 3.0

14 16 2.8

13 15 2.6

12 14 2.4

11 13 2.2

Charge Timec( s)

Delivereda/ Programmed Stored

Energy ( J)

Charge

Timec( s)

2 2.4 0.4

1.8 2.2 0.4

1.6 2.0 0.3

1.4 1.7 0.3

1.2 1.5 0.2

1.0 1.2 0.2

0.8 1.0 0.2

0.6 0.8 0.1

0.4 0.5 0.1

Energy delivered at connector block into a 75 Ù load.

Energy stored at end of charge on capacitor.

Typical charge time at Beginning of Life (BOL) with fully formed capacitors, rounded to the nearest tenth

of a second.

1.7 Stored data and diagnostics

Table 1-8. Stored data and diagnostics

Episode data

Tachy episodes 150 VF/VT/FVT episodes: intervals, text, EGM

EGM capacity for tachy episodes 14 min of dual-channel EGM or 23.5 min of single-channel

SVT/NST episodes 50 SVT/NST episodes: intervals, text, EGM (the device

EGM capacity for SVT/NST episodes

EGM sources 14 options: atrial/ RV / LV / far-field

EGM options Store before onset; Store during charging

Flashback memory 2000 intervals (containing both A-A and V-V): before latest

Mode switch episodes 53 mode switch episodes (fastest, longest, first and 50

EGM

does not usually store detailed episode records for NST episodes)

2 min of dual-channel EGM or 3.6 min of single-channel EGM

VF, before latest VT, and before interrogation

latest): episode text

INSYNC MAXIMO™7304 Reference Manual

Table 1-8. Stored data and diagnostics (continued)

1Quick reference

Stored data and diagnostics

Ventricular sensing episodes 9 ventricular sensing episodes (longest, first, and 7 latest):

Counter data

Detection counters Lifetime total, since cleared, and since last session

Episode counters Episodes:

Therapy efficacy counters Counts for each VF, FVT, VT Therapy:

Other stored data

Patient Alert — System events Up to 10 log entries: text and date for the first time an alert

Battery and lead measurements Battery voltage, last capacitor formation, last charge,

Lead performance trends 14 days of daily measurements plus 80 weeks of weekly

intervals, markers, and counter data text

VF, FVT, and VT

•

Atrial Fibrillation/Atrial Flutter episodes

•

Sinus Tach episodes

•

Other 1:1 SVT episodes

•

NST episodes

•

Mode switch episodes

•

Percentage pacing:

AS-VS, AS-VP, AP-VS, AP-VP percentages

•

Additional counters:

Single PVCs and PVC runs

•

Rate stabilization pulses and runs

•

Delivered

•

Successful

•

Unsuccessful

•

Intervention (manually aborted)

•

Total number of aborted shocks

is triggered between interrogations

lead impedance, EGM amplitude measurements, last high-voltage therapy, and sensing integrity counter

minimum and maximum measurements:

Lead impedance: atrial pacing, RV pacing, LV pacing,

•

defibrillation pathway, and SVC lead (if used) atrial EGM amplitude: (P-waves)

•

INSYNC MAXIMO™7304 Reference Manual

Chapter 1

New and enhanced features

Table 1-8. Stored data and diagnostics (continued)

Rate Histograms

Cardiac Compass trends 14 months of daily measurements:

Atrial rate

•

Ventricular rate

•

Ventricular rate during AT/AF

•

VT and VF episodes per day

•

one or more high-voltage therapy delivered

•

ventricular rate during VT or VF

•

episodes of non-sustained tachycardia per day

•

heart rate variability

•

total daily time in AT/AF

•

ventricular rate during AT/AF

•

percent pacing per day

•

patient activity

•

average day and night ventricular heart rate

•

1.8 New and enhanced features

The following features are new or changed from the 7289 InSync II Marquis ICD.

1.8.1 Tachyarrhythmia therapy

Output – The InSync Maximo has a maximum delivered energy

of 35 J.

1.8.2 Cardiac resynchronization therapy

Sequential biventricular pacing – The ventricular sequence

and V-V pace delay are programmable to support improved hemodynamics.

Pacing outputs for RV and LV are independently programmable.

INSYNC MAXIMO™7304 Reference Manual

2The InSync Maximo system

2.1 System overview 26

2.2 Indications and usage 29

2.3 Contraindications 30

2.4 Patient screening 30

Chapter 2

System overview

2.1 System overview

The Model 7304 InSync Maximo dual chamber implantable cardioverter defibrillator with cardiac resynchronization therapy (CRT ICD), including sequential biventricular pacing, is an implantable medical device system that includes 3 major components:

CRT ICD device

•

leads

•

programmer, software, and accessories

•

Each is described in detail below.

Device – The device senses the electrical activity of the patient’s heart using the sensing electrodes of the implanted atrial and right ventricular leads. It then analyzes the heart rhythm based on selectable sensing and detection parameters. The device provides the following functions:

simultaneous or sequential biventricular pacing for cardiac

•

resynchronization

automatic detection and treatment of ventricular

•

tachyarrhythmias (ventricular fibrillation, ventricular tachycardia, and fast ventricular tachycardia) with defibrillation, cardioversion, and antitachycardia pacing therapies

single or dual chamber pacing for patients requiring rate

•

support

diagnostics and monitors that evaluate the system and

•

assist in patient care

Leads – The device can be used with transvenous or epicardial defibrillation leads. The lead system should consist of bipolar or paired unipolar pacing/sensing leads in the right atrium and right ventricle of the heart, a pacing lead for the left ventricle, and 1 or 2 high-voltage cardioversion/defibrillation electrodes. In addition to the lead system, the Active Can acts as one of the high-voltage electrodes. The device delivers pacing and cardiac resynchronization therapy via the atrial (A), right ventricular (RV), and left ventricular (LV) leads. The device senses using the atrial and RV leads. Cardioversion/defibrillation therapy is delivered with 2 lead-based high-voltage electrodes, or with the Active Can and 1 or 2 lead-based high-voltage electrodes.

INSYNC MAXIMO™7304 Reference Manual

2The InSync Maximo system

System overview

Programmer and software – The Medtronic CareLink Programmer, Model 2090,1and Model 9998 software application allow you to perform the following functions:

configure the cardiac resynchronization, arrhythmia detection

•

and therapy, and bradycardia features for your patient

perform electrophysiological studies and system tests

•

monitor, display, or print patient cardiac activity information

•

For information about:

indications, contraindications, warnings and precautions,

•

see the implant manual that accompanies the device.

basic programmer and software desktop functions

•

that are not included in Chapter 10, “Using the programmer”, page 217, see the manual accompanying the programmer.

installing the Model 2067 or Model 2067L programming

•

head, see the manuals accompanying the programming heads.

implanting leads and using implant tools, refer to the

•

manuals accompanying the leads and implant tools.

2.1.1 Cardiac resynchronization

To improve cardiac output in patients with ventricular dysynchrony, the device provides biventricular pacing. The device paces either the right ventricle or both ventricles as programmed, unless pacing is inhibited by a sensed event in the RV.

Ventricular pacing sequence, V-V pace delay and LV pacing

•

vector are programmable.

Optional CRT features promote sustained resynchronization

•

pacing that could be interrupted during episodes of accelerated AV conduction, atrial rate excursions, PVCs, or atrial arrhythmia.

Pacing amplitudes and pulse widths are selected

•

independently for each ventricle.

With the model 2067 programming head

INSYNC MAXIMO™7304 Reference Manual

Chapter 2

System overview

2.1.2 Detecting and treating tachyarrhythmias

The device monitors the cardiac rhythm for short ventricular intervals that may indicate the presence of VF, VT, or FVT.

Upon detection of VF, the device delivers a biphasic

•

defibrillation shock of up to 35 J. If the VF episode persists, up to 5 more individually programmed defibrillation shocks can be delivered.

Upon detection of VT, the device delivers either a Ramp,

•

Ramp+, or Burst antitachycardia pacing therapy or a biphasic cardioversion shock of up to 35 J synchronized to a ventricular depolarization. If the VT episode persists, up to 5 more individually programmed VT therapies can be delivered. You can also program the device to monitor the VT episode without delivering therapy.

Upon detection of FVT, the device delivers either a Ramp,

•

Ramp+, or Burst antitachycardia pacing therapy or a biphasic cardioversion shock of up to 35 J synchronized to a ventricular depolarization. If the FVT episode persists, up to 5 more individually programmed FVT therapies can be delivered.

You can program the device to distinguish between true ventricular arrhythmias and rapidly conducted supraventricular tachyarrhythmias (SVT) and withhold therapy for SVT.

SVT discrimination includes the capability to detect a double tachycardia (an unrelated ventricular arrhythmia occurring simultaneously with an SVT) so that therapy is not withheld for a ventricular arrhythmia in the presence of an SVT.

2.1.3 Treating bradycardia

The device provides rate responsive pacing to optimize hemodynamics. An internal accelerometer senses the patient’s physical activity, allowing the device to increase and decrease the pacing rate in response to changes in the level of activity.

INSYNC MAXIMO™7304 Reference Manual

2.1.4 Monitoring for real-time and stored data

The device and programmer provide real-time information on detection and therapy parameters and status during a patient session. The device also provides accumulated data on device operation, including ventricular sensing episodes, stored electrograms, detected and treated tachyarrhythmia episodes, bradycardia interventions, and the efficacy of therapy. The Cardiac Compass report provides up to 14 months of clinically significant data, including physical activity, heart rate, percent pacing, arrhythmia episodes, and therapies delivered.

All of this information can be printed and retained in the patient’s file or saved in electronic format on a floppy diskette.

2.1.5 Conducting electrophysiologic tests

You can use the system to conduct non-invasive electrophysiologic studies, including manual delivery of any of the device therapies to manage an induced or spontaneous tachyarrhythmia.

2.1.6 Alerting the patient to system events

2The InSync Maximo system

Indications and usage

You can use the programmable Patient Alert monitoring feature to notify the patient with audible tones if certain conditions related to the leads, battery, charge time, and therapies occur. The patient can then respond based on your prescribed instructions.

2.2 Indications and usage

The InSync Maximo is indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life threatening ventricular arrhythmias. The system is also indicated for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy and have a left ventricular ejection fraction ≤ 35% and a prolonged QRS duration.

INSYNC MAXIMO™7304 Reference Manual

Chapter 2

Contraindications

2.3 Contraindications

2.4 Patient screening

Do not use the InSync Maximo system in:

Patients whose ventricular tachyarrythmias may have

•

transient or reversible causes, such as:

– acute myocardial infarction

– digitalis intoxication

– drowning

– electric shock

– electrolyte imbalance

– hypoxia

– sepsis

Patients with incessant VT or VF

•

Patients who have a unipolar pacemaker.

•

Before implant, patients should undergo a complete cardiac evaluation, including electrophysiologic testing. Also, electrophysiologic evaluation and testing of the safety and efficacy of the proposed tachyarrhythmia therapies are recommended during and after device implant.

Other optional screening procedures could include exercise stress testing to determine the patient’s maximum sinus rate, and cardiac catheterization to determine if there is a need for concomitant surgery and/or medical therapy.

INSYNC MAXIMO™7304 Reference Manual

3Emergency therapy

3.1 Delivering emergency therapies 32

3.2 Delivering an emergency defibrillation therapy 33

3.3 Delivering an emergency cardioversion therapy 34

3.4 Delivering emergency fixed burst pacing 34

3.5 Enabling emergency VVI pacing 35

Chapter 3

Delivering emergency therapies

3.1 Delivering emergency therapies

The device provides the following emergency therapies:

defibrillation

•

cardioversion

•

fixed burst pacing

•

emergency VVI pacing

•

The default emergency therapy is 35 J defibrillation. When you select [Emergency] and [DELIVER], the device charges and delivers a biphasic 35 J shock along the AX>B pathway.

The programmer resets the emergency defibrillation energy to 35 J each time you select [Emergency]. Emergency cardioversion and fixed burst values remain as selected for the duration of the session.

To return to other programming functions from an Emergency screen, select [Exit Emergency].

3.1.1 Effect on system operation

The device suspends the automatic detection features when emergency defibrillation, cardioversion, or fixed burst pacing therapies are delivered. Detection is not suspended during emergency VVI pacing. Removing the programming head or pressing [Resume] turns detection on again.

3.1.2 Aborting an emergency therapy

As a safety precaution, the programmer also displays an [ABORT] button, which immediately terminates any emergency therapy in progress.

3.1.3 Mechanical Emergency VVI button on the Medtronic CareLink Model 2090 programmer

If you press the red Emergency VVI button on the programmer display panel, the device initiates Emergency VVI pacing and the programmer displays the Emergency screen.

If Active Can is turned off, the defibrillation is delivered between the HVX and HVB electrodes.

INSYNC MAXIMO™7304 Reference Manual

3.1.4 Temporary parameter values

3Emergency therapy

Delivering an emergency defibrillation therapy

Emergency tachyarrhythmia therapies use temporary values that do not change the programmed parameters of the device. These values are not in effect until you select [DELIVER]. After the tachyarrhythmia therapy is complete, the device reverts to its programmed values.

3.2 Delivering an emergency defibrillation therapy

The default emergency therapy is a full-energy defibrillation. When you select [Emergency] and [DELIVER], the device charges and delivers a biphasic full-energy shock. The programmer sets the emergency defibrillation energy to its maximum value each time you select [Emergency] or select the [Defibrillation] option from an Emergency screen.

3.2.1 How to deliver emergency defibrillation

1. Position the programming head over the device.

2. Select [Emergency].

3. Accept the defibrillation energy shown on the screen, or select a new Energy value.

4. Select [DELIVER].

If delivery is not confirmed, verify that the programming head is properly positioned, and select [Retry] or [Cancel].

Delivery of Emergency VVI Pacing changes the programmed bradycardia pacing values to the emergency values (see Section 3.5, page 35).

INSYNC MAXIMO™7304 Reference Manual

Chapter 3

Delivering an emergency cardioversion therapy

3.3 Delivering an emergency cardioversion therapy

When you initiate an emergency cardioversion therapy, the device charges its capacitors to the selected energy and attempts to deliver therapy synchronized with a sensed tachyarrhythmia event. If the cardioversion therapy cannot be synchronized, it is aborted. See Section 7.3.5.6, page 136.

3.3.1 How to deliver emergency cardioversion

1. Position the programming head over the device.

2. Select [Emergency].

3. Select [Cardioversion].

4. Accept the defibrillation energy shown on the screen, or select a new Energy value.

5. Select [DELIVER].

If delivery is not confirmed, verify that the programming head is properly positioned and select [Retry] or [Cancel].

3.4 Delivering emergency fixed burst pacing

Emergency fixed burst pacing delivers maximum output pacing pulses to the ventricle at a selectable interval. The therapy continues for as long as you keep the programmer stylus on the [BURST Press and Hold] button.

INSYNC MAXIMO™7304 Reference Manual

Enabling emergency VVI pacing

3.4.1 How to deliver emergency fixed burst pacing

1. Position the programming head over the device.

2. Select [Emergency].

3. Select [Fixed Burst].

4. Accept the pacing interval shown on the screen, or select a new interval value.

5. Select [BURST Press and Hold].

If delivery is not confirmed, the programmer displays an error window. Verify that the programming head is properly positioned. Select [OK] from the window and reselect [BURST Press and Hold].

3.5 Enabling emergency VVI pacing

3Emergency therapy

Emergency VVI pacing programs the device to deliver high-output ventricular pacing. You can initiate emergency VVI pacing from the Emergency screen or by pressing the red mechanical button on the Medtronic CareLink Model 2090 programmer display panel. To disable emergency VVI pacing, reprogram the bradycardia pacing parameters from the Parameters screen.

INSYNC MAXIMO™7304 Reference Manual

Chapter 3

Enabling emergency VVI pacing

3.5.1 How to deliver emergency VVI pacing

1. Position the programming head over the device.

2. Select [Emergency].

3. Select [VVI Pacing].

4. Select [PROGRAM]. A successful programming sets the device to the following maximum output bradycardia pacing values:

Pacing Mode: VVI

•

Lower Rate: 70 ppm

•

RV. Amplitude: 6 V

•

RV. Pulse Width: 1.6 ms

•

V. Pace Blanking: 240 ms

•

V. Pacing: RV

•

V. Sense Response: Off

•

Ventricular Rate

•

Stabilization: Off Cond AF Response: Off

•

If programming is not confirmed, verify that the programming head is properly positioned and select [Retry] or [Cancel].

INSYNC MAXIMO™7304 Reference Manual

Device implant and patient follow-up procedures

Part II

4Implanting the device

4.1 Overview 40

4.2 Preparing for an implant 40

4.3 Replacing a device 42

4.4 Surgical approach 43

4.5 Sensing and pacing measurements 47

4.6 Connecting the leads to the device 47

4.7 Testing defibrillation operation and effectiveness 51

4.8 Positioning and securing the device 54

4.9 Completing the implant procedure 54

Chapter 4

Overview

4.1 Overview

The tasks for implanting a device include:

1. Preparing for an implant

2. Replacing a device

3. Surgical approach

4. Sensing and pacing measurements

5. Connecting the leads to the device

6. Testing defibrillation operation and effectiveness

7. Positioning and securing the device

8. Completing the implant procedure

These tasks are described in the sections that follow.

4.2 Preparing for an implant

Warning: Keep a backup external defibrillator available

during the implant for transthoracic rescue when arrhythmias are induced.

Warning: Do not permit the patient to contact grounded equipment that could produce hazardous leakage current during implant. Resulting arrhythmia induction could result in the patient’s death.

The device is intended for implant with Medtronic transvenous or epicardial leads. No claims of safety and efficacy can be made with regard to other acutely or chronically implanted lead systems that are not manufactured by Medtronic.

4.2.1 Equipment for an implant

Medtronic CareLink Programmer Model 2090 and Model

•

2067or 2067L programming head

Model 9998 software application

•

Model 8090 Analyzer lead analysis device or equivalent

•

pacing system analyzer

external defibrillator

•

INSYNC MAXIMO™7304 Reference Manual

Model 5358 Defibrillator Implant Support Device and

•

software application (optional)

4.2.2 Sterile supplies

InSync Maximo and lead system components

•

Programming head sleeve or programming head

•

Analyzer cables

•

Lead introducers or delivery systems appropriate for the

•

lead system

Extra stylets of appropriate length and shape

•

4.2.3 How to set up the implant support instrument

When using an implant support instrument such as the Model 5358 Defibrillator Implant Support device:

1. Calibrate any monitoring or recording equipment while recording the EGM and marker outputs of the support instrument.

2. Verify the high-energy output of the support instrument by delivering a high-energy defibrillation shock into the test load.

4Implanting the device

Preparing for an implant

4.2.4 How to set up the programmer and start the application

1. Set up the programmer as described in the instructions provided with the programmer.

2. Install the InSync Maximo Model 9998 software on the programmer if it is not already installed.

3. Place the programming head over the device, and start the application. Select the device model or select [Auto identify].

Note: The programmer automatically interrogates the device when the application starts.

INSYNC MAXIMO™7304 Reference Manual

Chapter 4

Replacing a device

4.2.5 How to preprogram the device

Before opening the sterile package, prepare the device for implant as follows:

1. Check the “Use by” date printed on the package. Do not implant the device after the “Use by” date because the battery’s longevity can be reduced.

2. Interrogate the device and print a full summary report.

Note: If the programmer reports that an electrical reset occurred, do not implant the device. Contact a Medtronic representative.

3. Confirm that the battery voltage is at least 3.0 V at room temperature.

If the device temperature is lower than room temperature or has delivered a recent high-voltage charge, the battery voltage will be temporarily lower.

4. Set up data collection parameters and the device internal clock (see Section 12.9.3, “How to set up data collection”, page 305).

5. Perform a manual capacitor formation (see “Manual capacitor formation”, page 325).

6. Program the therapy and pacing parameters to values appropriate for the patient. Ensure that all tachyarrhythmia detection is programmed Off (see Section 8.1.4, “How to program CRT and bradycardia pacing parameters”, page 151).

Note: Do not enable VF Detection until the device has been successfully implanted.

4.3 Replacing a device

If you are replacing a previously implanted device, turn off device detection and therapies before explanting.

When implanting the device with a chronic lead system, perform the following evaluations to ensure appropriate detection and therapy:

Check the integrity of the chronic high-voltage leads with a

•

test shock, chest x-ray, and inspection.

Perform chronic pacing and sensing measurements.

•

Measure high-voltage lead impedances.

•

Test defibrillation efficacy.

•

Use the Quick Look screen to verify the voltage; see Section 11.2.2, “Quick Look observations”, page 253.

INSYNC MAXIMO™7304 Reference Manual

Confirm adequate sensing during VF.

•

Ensure proper fit of the lead connectors in the device

•

connector block.

Notes:

To meet the implant requirements, it may be necessary to

•

reposition or replace the chronic leads or to add a third high-voltage electrode.

Any unused leads that remain implanted must be capped.

•

4.3.1 How to explant and replace a device

1. Program all tachyarrhythmia detection Off.

2. Dissect the leads and the device free from the surrounding tissues in the surgical pocket. Be careful not to nick or breach the lead insulation during the process of exposing the system.

3. Loosen each setscrew, and gently retract the lead from the connector block.

4. Remove the device from the surgical pocket.

5. If the connector pin of any implanted lead shows signs of pitting or corrosion, replace the implanted lead with a new lead. The damaged lead should be discarded and replaced to assure the integrity of the device system.

6. Measure sensing, pacing, and defibrillation efficacy using the replacement device or an implant support instrument.

4Implanting the device

Surgical approach

4.4 Surgical approach

The InSync Maximo system typically requires a left ventricular lead implant in the coronary sinus and positioned in a cardiac vein. For this reason, physicians should expect that implanting an InSync Maximo system will require more time than implanting a traditional ICD or pacemaker system.

4.4.1 Implanting the device

In most cases the device is implanted in the pectoral region, either submuscularly or subcutaneously, using transvenous leads for pacing, sensing, and high-voltage therapies.

INSYNC MAXIMO™7304 Reference Manual

Chapter 4

Surgical approach

4.4.2 Lead configurations

Follow these single-incision guidelines when implanting the device in the pectoral region. The pocket should be about 1.5 times the size of the device.

Submuscular approach: A single incision that extends over

•

the delta-pectoral groove can provide access to the cephalic and subclavian veins and access to form the implant pocket. Place the device sufficiently medial to the humeral head to avoid interference with shoulder motion.

Subcutaneous approach: The subcutaneous approach can

•

be similar to a pacemaker implant, using a single transverse incision long enough to permit isolation of the cephalic and subclavian veins. Place the device quite far medially to keep the leads away from the axilla, and keep the upper edge of the device inferior to the incision.

The device is typically implanted with the following leads:

one transvenous lead for the left ventricle (LV) for pacing

•

one bipolar transvenous lead in the right ventricle (RV) for

•

sensing, pacing, and cardioversion/defibrillation therapies

one bipolar transvenous lead in the atrium (A) for sensing

•

and pacing

The InSync Maximo is an Active Can system in which the device case serves as a high-voltage electrode. The device case, the RV coil, and the SVC coil form a 3 electrode system for simultaneous mode defibrillation and cardioversion. High-voltage therapies are delivered between the RV coil and the combined device case and SVC coil.

The device may be implanted with other transvenous leads. Refer to Section 4.4.4, “Using other transvenous leads”, page 46, for more information.

Notes:

Medtronic 3.2 mm low-profile leads are not directly

•

compatible with the device IS-1 connector block.

For questions about lead and device compatibility, please

•

contact your Medtronic representative.

INSYNC MAXIMO™7304 Reference Manual

4.4.3 Implanting the lead

Note: Do not implant the LV, atrial, and RV leads in the same

venous access site. Medtronic recommends implanting the LV lead in the subclavian vein, and the atrial and RV leads in the cephalic vein.

If inserting using a subclavian approach, position the lead laterally to avoid pinching the lead body between the clavicle and the first rib. Pinching the lead may eventually cause conductor fracture, damage to the insulation, or other damage to the lead. This may result in complications such as loss of detection, loss of pacing therapies, or loss of cardioversion/defibrillation therapy.

Certain anatomical abnormalities, such as thoracic outlet syndrome, may also cause pinching and subsequent fracture of the lead. If significant resistance is encountered during a subclavian stick implant procedure, do not force passage of the lead by adjusting the patient’s posture (by raising the arm or putting a towel behind the person’s back, for example). Use an alternate venous entry site instead.

4.4.3.1 Implanting the ventricular leads

4Implanting the device

Surgical approach

Warning: Backup pacing should be readily available during implant. Use of the delivery system or leads may cause heart block.

Note: Due to the variability of cardiac venous systems, the venous anatomy should be assessed before implanting the LV lead to determine an optimal LV lead position. Before placing a lead in the coronary sinus, obtain a venogram.

When implanting a LV or RV lead, follow the directions for use in the respective lead technical manuals.

Final lead positioning should attempt to optimize both cardiac resynchronization and defibrillation threshold.

When pacing at 10 V using an external pacing device, test for extracardiac stimulation from the LV lead. If extracardiac stimulation is present, consider repositioning the lead.

4.4.3.2 Implanting the right atrial lead

Implant the atrial lead in the cephalic vein, if possible. Follow the directions for use in the lead technical manual.

INSYNC MAXIMO™7304 Reference Manual

Chapter 4

Surgical approach

4.4.3.3 Lead positioning

For the initial lead configuration the following positions are recommended:

LV tip electrode – Position as far laterally into the coronary venous system as possible (deflection of the LV EGM signal as late as possible in the QRS complex).

RV tip electrode – Position as far apically as possible (deflection of the RV EGM signal on the RV electrode should start early in the QRS complex). Defibrillation threshold, atrial far-field sensing and RV-LV timing must be considered when choosing the optimal location.

Atrial tip electrode – The atrial tip electrode should be positioned close to the SA node or on the lateral wall to minimize the possibility of far-field R-wave oversensing. Lead placement in these positions potentially provides optimal atrial sensing while reducing far-field R-wave sensing.

4.4.4 Using other transvenous leads

Follow the general guidelines below for initial positioning of other transvenous leads (the final positions are determined by defibrillation efficacy tests):

For an SVC lead, place the lead tip high in the innominate

•

vein, approximately 5 cm proximal to the atrium (A) and SVC junction.

For an SQ patch lead, place the patch along the left

•

midaxillary line, centered over the fourth-to-fifth intercostal space.

4.4.5 Epicardial lead systems

The following guidelines should be observed:

The distance between the RVring electrode and the RVtip

•

electrode should not exceed 1 cm.

The RVtip electrode should not lie in a direct path between

•

epicardial patches.

The RVtip/RVring and Atip/Aring intrinsic, post-pace, and

•

post shock electrograms should be thoroughly evaluated for oversensing, undersensing, cross-talk, and noise.

INSYNC MAXIMO™7304 Reference Manual

4Implanting the device

Sensing and pacing measurements

The pacing thresholds and electrogram characteristics

•

should meet the values indicated in Table 4-1.

4.5 Sensing and pacing measurements

Sensing and pacing measurements include EGM amplitudes, slew rates, capture thresholds, and pacing lead impedances. Medtronic recommends using the Model 8090 Analyzer for sensing and pacing measurements. Refer to the Analyzer technical manual for detailed procedures on performing these measurements.

Do not use the intracardiac EGM telemetered from the device to assess sensing.

Table 4-1 lists the acceptable implant values for acute and chronically implanted lead systems.

Table 4-1. Acceptable implant values

Measurement required

EGM amplitude (during NSR)

Slew rate

Capture threshold (0.5 ms pulse

width)

Typical pacing lead impedance

Verify adequate pacing threshold margins at implant and at each followup visit.

The measured pacing lead impedance is a reflection of measuring equipment and lead technology.

Please refer to specific lead technical manuals for acceptable impedance values.

Acute

≥ 2 mV

≥

0.5 V/s

≤ 1.5 V

250 - 1000 Ùc(all)

≥ 5 mV

≥

0.75 V/s

≤ 1.0 V

≥ 3 mV

—

≤ 3.0 V

Chronic

≥ 1 mV

≥

0.3 V/s

≤ 3.0 V

≥ 3 mV

≥

0.5 V/s

≤ 3.0 V

≥ 1 mV

—

≤ 4.0 V

4.6 Connecting the leads to the device

For more detailed information about lead/connector compatibility, see the Medtronic representative.

InSync Maximo 7304 Implant Manual

INSYNC MAXIMO™7304 Reference Manual

, or contact your

Chapter 4

Connecting the leads to the device

Table 4-2. Lead connections

Device port Connector type Software name

SVC (HVX) DF-1 SVC

RV (HVB) DF-1 RVcoil

Can

RV IS-1 bipolar RVtip and RVring

LV IS-1 bipolar LVtip and LVring

A IS-1 bipolar Atip and Aring

Figure 4-1. Lead connections

—

Can

1 SVC (HVX) 2 RV (HVB) 3 Can (HVA) 4 LV 5 RV 6 A

Caution: Loose lead connections may result in inappropriate sensing and failure to deliver necessary arrhythmia therapy.

INSYNC MAXIMO™7304 Reference Manual

4Implanting the device

Connecting the leads to the device

Cautions:

To ensure appropriate sensing and detection, insert the

•

right ventricular lead IS-1 connector into the RV port and insert the right ventricular lead DF-1 connector into the RV (HVB) port.

If no SVC electrode is implanted, the pin plug provided

•

with the device must be secured in the SVC (HVX) port.

Use only the torque wrench supplied with the device.

•

It is designed to prevent damage to the device from overtightening a setscrew.

Do not reuse the torque wrench after this implant.

•

Lead and Active Can electrodes in electrical contact

•

with each other during a high-voltage therapy could cause current to bypass the heart, possibly damaging the device and leads. While the device is connected to the leads, make sure that no therapeutic electrodes, stylets, or guide wires are touching or connected by an accessory low impedance conductive pathway. Move any objects that contain conductive materials (e.g., an implanted guide wire) well away from all electrodes before a high-voltage shock is delivered.

Notes:

For easier lead insertion, insert the LV IS-1 lead before the

•

other leads.

If a chronic lead system uses a different size or number of

•

leads, insert the lead connectors into appropriate adaptors. See the appropriate lead technical manuals for more details.

Upon initial lead connection to the connector block, LVtip,

•

RVtip, and RVcoil all need to be connected within the connector block to provide biventricular pacing.

INSYNC MAXIMO™7304 Reference Manual

Chapter 4

Connecting the leads to the device

4.6.1 How to connect the lead to the device

1. Insert the torque wrench into the appropriate setscrew.

a. If the port is obstructed by

the setscrew, retract the setscrew to clear it. Take care not to disengage the setscrew from the connector block.

b. Leave the torque wrench in

the setscrew until the lead is secure. This allows a pathway for venting trapped air when the lead is inserted.

2. Push the lead or plug into the connector port until the lead pin is clearly visible in the pin viewing area. No sealant is required, but sterile water may be used as a lubricant.

3. Tighten the setscrew by turning clockwise until the torque wrench clicks.

4. Tug gently on the lead to confirm a secure fit. Do not tug on the lead until all setscrews have been tightened.

5. Repeat these steps for each connector port.

4.6.2 Post pace oversensing testing

Changes in the programmed ventricular pacing configuration (RV, RV→LV, or LV→RV) may evoke slightly different EGMs. To ensure proper sensing regardless of the pacing configuration, or in the

INSYNC MAXIMO™7304 Reference Manual

event of lead dislodgment or failure, the sensing behavior during pacing for all configurations should be evaluated as follows:

1. Program RV Pacing.

2. Print a 10 to 30 s test strip.

3. Check for post pace oversensing.

Repeat Step 1 through Step 3 with ventricular pacing programmed to RV→LV and LV→RV.

4Implanting the device

Testing defibrillation operation and effectiveness

If oversensing occurs during one of the pacing configurations, repositioning of the RV lead may help alleviate the oversensing.

4.7 Testing defibrillation operation and effectiveness

Demonstrate reliable defibrillation effectiveness with the implanted lead system by using your preferred method to establish that a 10 J (minimum) safety margin exists.

Note: If the 10 J (minimum) safety margin cannot be ensured, see Section 15.5, “Solving tachyarrhythmia therapy problems”, page 350.

4.7.1 High-voltage implant values

Measured values must meet the following requirements at implant.

Table 4-3. High-voltage therapy values at implant

Measurement Acute or Chronic Leads

V. Defib impedance

SVC (HVX) impedance (if applicable)

Defibrillation threshold ≤ 25 J

20 – 200 Ù

Warning: Ensure that an external defibrillator is charged for a rescue shock.

INSYNC MAXIMO™7304 Reference Manual

Chapter 4

Testing defibrillation operation and effectiveness

4.7.2 How to prepare for defibrillation threshold testing

1. Place the programming head over the device, start a patient session, and interrogate the device, if you have not already done so.

2. Observe the Marker Channel telemetry annotations and the programmer ECG display to verify that the device is sensing properly.

3. Conduct a manual Lead Impedance Test2to verify the defibrillation lead connections. Perform this test with the device in the surgical pocket, and keep the pocket very moist. If the impedance is out of range, perform one or more of the following tasks:

Recheck lead connections and electrode placement.

•

Repeat the measurement.

•

Inspect the bipolar EGM for abnormalities.

•

Measure the defibrillation impedance with a manual test shock.

•

4. Program the device or support instrument to properly detect VF with an adequate safety margin (1.2 mV sensitivity).

See Section 13.4, “Measuring lead impedance”, page 320 .

INSYNC MAXIMO™7304 Reference Manual

Testing defibrillation operation and effectiveness

4.7.3 How to perform defibrillation threshold testing

4Implanting the device

1. Select Tests > EP Study.

2. Select either 50 Hz BURST or T-shock induction.

3. Select [Resume at BURST] or [Resume at DELIVER].

4. Select [Adjust Permanent…].

5. Program VF Enable On.

6. Program the automatic therapy energy settings. Therapies 2-6 should be set to the maximum energy.

7. Select [Program].

8. Select [Close].

9. If performing a T-Shock induction, select the [Enable] checkbox.

10. Select [DELIVER], or [50 Hz BURST Press and Hold].

If necessary, you can abort an induction or therapy in progress by pressing [ABORT].

11. Observe the live rhythm monitor for proper post-shock sensing.

12. Use the [Adjust Permanent…] button to program the next appropriate energy level.

13. Wait until the on-screen timer reaches 5 min, then repeat Step 9 through Step 12 as needed.

14. Select Params > Detection and program VF, FVT, and VT detection Off before closing.

INSYNC MAXIMO™7304 Reference Manual

Chapter 4

Positioning and securing the device

4.8 Positioning and securing the device

Cautions:

If no SVC electrode is implanted, the pin plug provided

•

with the device must be secured in the SVC (HVX) port.

Program tachyarrhythmia detection Off before closing.

•

4.8.1 How to position and secure the device

1. Ensure that each lead pin or plug is fully inserted into the connector block and that all setscrews are tight.

2. Coil any excess lead length beneath the device. Avoid kinks in the lead conductors.

3. Implant the device within 5 cm of the skin and with the Medtronic label facing the skin for improved Patient Alert volume. This position optimizes the ambulatory monitoring operations.

4. Use nonabsorbable sutures to secure the device within the pocket to minimize post-implant rotation and migration of the device. Use a surgical needle to penetrate the suture holes.

4.9 Completing the implant procedure

After implanting the device, x-ray the patient to verify device and lead placement. To complete programming the device, select parameters that are appropriate for the patient.

INSYNC MAXIMO™7304 Reference Manual

Completing the implant procedure

4.9.1 How to complete programming the device

1. After closing the pocket, program detection On. Program ventricular tachyarrhythmia therapies On as desired.

2. Do not enable the Other 1:1 SVTs PR Logic detection criterion until the atrial lead has matured (approximately 1 month post implant).

3. If external equipment was used to conduct the defibrillation efficacy tests, perform a final VF induction, and allow the implanted system to detect and treat the arrhythmia.

4. Monitor the patient after the implant, and take x-rays as soon as possible to document and assess the location of the leads.

5. Program patient information. See Section 12.10, “Viewing and entering patient information”, page 308.

6. Configure the Patient Alert feature. See Section 11.3, “Using the Patient Alert feature”, page 254.

7. Set up data collection parameters. See Section 12.9, “Setting up data collection”, page 302.

8. Interrogate the device after any spontaneous episodes to evaluate the detection and therapy parameter settings.

9. If the patient has not experienced spontaneous episodes, you may induce the clinical tachyarrhythmias using the non-invasive EP Study features to further assess the performance of the system. See Chapter 14, “Conducting Electrophysiologic Studies”, page 327.

10. Recheck pacing and sensing values, and adjust if necessary. See Section 13.3, “Measuring pacing thresholds”, page 317.

4Implanting the device

INSYNC MAXIMO™7304 Reference Manual

5Conducting a patient follow-up session

5.1 Patient follow-up guidelines 58

5.2 Verifying the status of the implanted system 59

5.3 Verifying effective cardiac resynchronization therapy 59

5.4 Verifying effective basic pacing 60

5.5 Verifying accurate detection and appropriate therapy for ventricular tachyarrhythmias 62

Chapter 5

Patient follow-up guidelines

5.1 Patient follow-up guidelines

Schedule regular patient follow-up sessions to monitor the condition of the device and leads and to verify that the device is configured appropriately for your patient.

During the first few months after receiving a new device, the patient may require close monitoring. Schedule an office visit at least every 3 months.

The Quick Look screen, which is displayed after you interrogate the device, provides a good beginning for the follow-up review. Using this screen you can perform the following tasks:

Verify that the device is functioning correctly.

•

Verify that the device is delivering biventricular pacing most

•

or all of the time.

Review the clinical performance and long term trends.

•

Print appropriate reports to compare the results to the

•

patient’s history and to retain for future reference.

For details about reviewing clinical trend data, see

Section 12.4, “Viewing the Heart Failure Management

•

report”, page 278

Section 12.5, “Viewing clinical trends in the Cardiac

•

Compass report”, page 282

Note: The Checklist feature displays a list of standard follow-up tasks on the programmer screen for easy reference during the follow-up session. You can also customize your own checklists if you wish. See Section 11.4, “Streamlining follow-ups with Checklist”, page 262, for more information.

INSYNC MAXIMO™7304 Reference Manual

5Conducting a patient follow-up session

Verifying the status of the implanted system

5.2 Verifying the status of the implanted system

To verify that the device and leads are functioning correctly, review the following information from the Quick Look screen and perform followup tests as indicated:

Review the displayed battery voltage for comparison to the

•

Elective Replacement Indicator value (see Section 1.4, “Replacement indicators”, page 20). Remember that battery voltage may be low if high-voltage charging has occurred within 24 hours.

Review the last full-energy charge.

•

– For information about adjusting the capacitor formation

interval, see Section 9.1, “Optimizing charge time”, page 210.

– If the programmer displays an Excessive Charge Time

ERI, the device should be replaced immediately.

Review the defibrillation and pacing lead impedance values

•

for inappropriate values or large changes since the last followup. See Section 13.4, “Measuring lead impedance”, page 320.

Perform an EGM Amplitude test in the RV and atrium for

•

comparison to previous EGM amplitude measurements. See Section 13.5.5, “How to perform an EGM Amplitude test”, page 324.

To review longer term trends in sensing and impedance

•

measurements, select the [>>] button from the lead performance area of the Quick Look screen. The programmer displays a detailed history of automatic sensing and impedance measurements. See Section 11.2, “Taking a quick look at device activity”, page 253.

5.3 Verifying effective cardiac resynchronization therapy

To verify that the device is providing cardiac resynchronization therapy appropriately, review the following information from the initial interrogation report or Quick Look screen and investigate as indicated:

Confirm that the patient is receiving adequate cardiac

•

support for daily living activities.

INSYNC MAXIMO™7304 Reference Manual

Chapter 5

Verifying effective basic pacing

5.3.1 Considerations

Review Quick Look Observations related to ventricular

•

pacing percentage or ventricular sensing episodes.

Check the stored Ventricular Sensing Episode records for

•

appropriate interventions and continuity of resynchronization pacing. See Section 12.7, “Viewing episode data”, page 291.

Check the rate histograms for more information on atrial and

•

ventricular pacing in general, and ventricular rates during AT/AF episodes.

Review the Heart Failure Management and Cardiac

•

Compass reports for comparison to patient history (see Section 12.4, “Viewing the Heart Failure Management report”, page 278).

Review the following information before assessing resynchronization therapy.

Undersensing, far-field oversensing, or loss of capture

•

are basic pacing issues that can affect delivery of cardiac resynchronization therapy. These situations can often be resolved with basic programming changes and then monitored for further occurrences.

If CRT delivery is lost during AF or during atrial rate

•

excursions, consider the following programming options:

– Perform basic programming changes to increase the

Upper Tracking Rate or decrease the total atrial refractory period (for information on total atrial refractory period, see Section 8.2.4, “Programming considerations for atrial rates”, page 162).

– Enable Ventricular Sense Response, Atrial Tracking

Recovery, or Conducted AF Response to promote more continuous delivery of CRT.

5.4 Verifying effective basic pacing

To verify that the device is sensing and pacing appropriately, review the following information from the Initial Interrogation Report, and Quick Look screen, and investigate as indicated:

Confirm that the patient is receiving adequate cardiac

•

support for daily living activities.

INSYNC MAXIMO™7304 Reference Manual

•

5.4.1 Considerations

Review the following information before verifying bradycardia pacing.

5Conducting a patient follow-up session

Verifying effective basic pacing

Review the pacing conduction history and rate histograms for comparison to the patient history. A sharp increase in the atrial pacing percentage may indicate a need for investigation and analysis.

Review the recorded Mode Switch episodes for comparison to the patient’s atrial arrhythmia history (see Section 12.7, “Viewing episode data”, page 291). A dramatic increase in frequency or duration of atrial episodes may indicate a need for investigation and analysis.

Review the Cardiac Compass report for comparison to patient history (see Section 12.5, “Viewing clinical trends in the Cardiac Compass report”, page 282).

Conduct pacing threshold tests (see Section 13.3, “Measuring pacing thresholds”, page 317) to verify that the programmed pacing outputs provide a sufficient safety margin.

Atrial pacing – If the conduction history or rate histograms show a predominance of atrial pacing despite a healthy sinus response, consider these options to decrease the atrial pacing burden:

Decrease the Lower Rate.

•

Decrease the rate response or increase the activity

•

threshold.

Conduction history – If the reported percentages in the conduction history do not add up to 100, the percentages may be rounded.

INSYNC MAXIMO™7304 Reference Manual

Chapter 5

Verifying accurate detection and appropriate therapy for ventricular tachyarrhythmias

5.5 Verifying accurate detection and appropriate therapy for ventricular tachyarrhythmias

To verify that the device is providing effective tachyarrhythmia detection and therapy, review the following information from the Quick Look screen and investigate as indicated:

Review Quick Look Observations that relate to patient

•

history and device operation. To display more detailed information about any observation, select the observation and then select the [>>] button.

Review any Patient Alerts listed in the Observations of the

•

Quick Look screen. For the most detailed information about Patient Alerts, select Patient Alert from the Data icon and select [Events].

Check stored episode records for appropriate sensing

•

and detection of arrhythmias. See Section 12.7, “Viewing episode data”, page 291.

Check stored SVT episode records for appropriate

•

identification of SVTs.

5.5.1 Considerations

Review the following information before verifying detection and therapy.

Flashback memory – In addition to the episode text and stored electrograms, use Flashback memory and interval plots to help investigate the accuracy and specificity of ventricular detection.

Episode misidentification – If the episode records indicate that false detections have occurred, the Sensing Integrity counter may help in determining the prevalence of oversensing. For more information, see Section 12.2.4.3, “Sensing integrity counter”, page 274.

If the device is oversensing, consider these programming options:

Increase the Pace Blanking value.

•

Increase the sensitivity threshold.

•

Caution: Do not reprogram the device to decrease oversensing without assuring that appropriate sensing is maintained. See Section 6.2, “Setting up sensing”, page 71.

INSYNC MAXIMO™7304 Reference Manual

5Conducting a patient follow-up session

Verifying accurate detection and appropriate therapy for ventricular tachyarrhythmias

If the episode records reveal that a stable monomorphic VT has been identified and treated as VF, consider these options to improve the detection accuracy:

Review the Interval Plot for the episode, and adjust the VF

•

Interval, if necessary. Use caution when reprogramming the VF Interval, because changes to this value can adversely affect VF detection.

Consider enabling FVT via VF detection. See Section 6.5,

•

“Detecting FVT episodes”, page 85.

If the SVT episode records include episodes of true VT, review the SVT episode record to identify the SVT detection criterion that withheld detection. Adjust the SVT detection criteria parameters as necessary. See Section 6.8, “Enhancing detection with PR Logic criteria”, page 96, and Section 6.9, “Enhancing VT detection with the Stability criterion”, page 104.

INSYNC MAXIMO™7304 Reference Manual

Configuring the device for the patient

Part III

6Detecting tachyarrhythmias

6.1 Detection overview 68

6.2 Setting up sensing 71

6.3 Detecting VF episodes 76

6.4 Detecting VT episodes 79

6.5 Detecting FVT episodes 85

6.6 Detecting tachyarrhythmia episodes with Combined Count 90

6.7 Monitoring episodes for termination or redetection 92

6.8 Enhancing detection with PR Logic criteria 96

6.9 Enhancing VT detection with the Stability criterion 104

6.10 Detecting double tachycardias 106

6.11 Detecting prolonged tachyarrhythmias with High Rate Timeout 107

Chapter 6

Detection overview

6.1 Detection overview

The device detects ventricular tachyarrhythmias (VF, VT, and FVT) by comparing the time intervals between sensed ventricular events to a set of programmable detection intervals. If enough intervals occur that are shorter than the programmed intervals, the device detects a tachyarrhythmia and responds automatically with a programmed therapy. After delivering the therapy, the device either redetects the arrhythmia and delivers the next programmed therapy or detects episode termination.

To avoid detecting rapidly conducted SVTs (for example, sinus tachycardia or atrial fibrillation) as ventricular tachyarrhythmias, the device provides several detection enhancements, including PR Logic and Stability detection criteria.

All of the detection features interact during initial detection (see Figure 6-1). During redetection, the device does not apply the PR Logic detection criteria.

Note: Detection functions can be turned off by programming the VF Enable, FVT Enable, and VT Enable parameters to Off. For an example, see Section 6.3.4, “How to program VF detection”, page 78.

INSYNC MAXIMO™7304 Reference Manual

6Detecting tachyarrhythmias

Ventricular Event

Yes

Update counts and pattern information

Is the interval in the VF, FVT, or VT detection zone?

Has High Rate Timeout suspended detection enhancements?

Does Stability reset the VT event count? (VT and FVT via VT

detection only)

Has a tachyarrhythmia event count reached an NID?

Are one or more PR Logic criteria on?

No/suspended by High Rate

Timeout

Tachy

Episode

Detected

Is the median ventricular interval less than the SVT Limit?

Is there a double tachycardia in progress?

Are one or more PR Logic criteria withholding detection?

Figure 6-1. How detection features interact during initial detection

Detection overview

6.1.1 Suspending tachyarrhythmia detection

When detection is suspended, the device temporarily stops classifying and counting tachyarrhythmia intervals. Sensing and programmed pacing remain active, and the programmed detection settings are not modified.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detection overview

Detection is suspended:

when the device senses the presence of a strong magnet.

•

The programmer head contains a magnet which suspends detection, but once telemetry between the device and programmer is established, detection resumes.

while performing any of the manual system tests, including

•

Underlying Rhythm, Pacing Threshold, Lead Impedance, EGM Amplitude, and Charge/Dump. Detection automatically resumes once the test is complete.

while performing a T-Shock, 50 Hz Burst, Manual Burst,

•

or PES Induction. You can choose to have the device automatically resume detection after delivering the induction.

when you deliver a Manual or Emergency therapy. You

•

can resume detection by selecting the [Resume] button or removing the programming head from the device.

when you select the on-screen [Suspend] button. You can

•

resume detection by selecting the [Resume] button or by removing the programming head from the device.

during the automatic daily lead impedance measurements.

•

Detection resumes when the measurements are complete.

while the device is delivering an automatic tachyarrhythmia

•

therapy (including capacitor charging for defibrillation and cardioversion). However, the device does continue to confirm the detected episode during charging. Detection resumes when the therapy is complete.

Note: The device suspends VT detection and Combined Count detection (see Section 6.6, “Detecting tachyarrhythmia episodes with Combined Count”, page 90) for 17 events following a defibrillation therapy delivered in response to a detected VF.

during charging for Automatic Capacitor Formation.

•

Detection resumes when charging is complete.

If the defibrillation therapy is delivered as a result of either a High Rate Timeout Therapy operation or Progressive Episode Therapies operation, VT detection is not suspended (see Section 6.11.4.1, “High Rate Timeout Therapy”, page 109).

INSYNC MAXIMO™7304 Reference Manual

6.2 Setting up sensing

The device provides bipolar sensing in both the atrium and right ventricle using the sensing electrodes of the implanted atrial and RV leads. You can adjust the sensitivity to intracardiac signals using independent atrial and ventricular sensitivity settings. These settings define the minimum electrical amplitude recognized by the device as an atrial or ventricular sensed event.

Proper sensing is essential for the safe and effective use of the device. To provide appropriate sensing, the device uses:

auto-adjusting atrial and ventricular sensing thresholds

•

short (30 ms) cross-chamber blanking after paced events

•

no cross-chamber blanking after sensed events

•

See Section 6.2.4, “Details about sensing”, page 74.

6.2.1 Parameters

6Detecting tachyarrhythmias

Setting up sensing

V. Sensitivity – Minimum amplitude of electrical signal that registers as a sensed ventricular event.

A. Sensitivity – Minimum amplitude of electrical signal that registers as a sensed atrial event.

6.2.2 Considerations

Review the following information before programming sensing parameters.

Dual chamber sensing and pacing modes – The device senses in both the atrium and the right ventricle at all times, except when the programmed bradycardia pacing mode is DOO. When the pacing mode is programmed to DOO or VOO mode, there is no sensing in the ventricle. mode, you must first disable detection.

Sensitivity thresholds – The programmed atrial and ventricular sensitivity thresholds apply to all features related to sensing, including detection and bradycardia pacing.

Atrial sensing occurs in VOO mode.

0.15; 0.3

0.6; 0.9; 1.2 mV

0.15; 0.3

0.6; 0.9; 1.2; 1.5;

2.1 mV

In order to program either DOO or VOO

; 0.45;

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Setting up sensing

Bradycardia pacing and sensing – A combination of high pacing pulse width or high amplitude with a low sensitivity threshold may cause inappropriate sensing across chambers or in the same chamber. Programming a lower pulse width, lower amplitude, longer pace blanking, or a higher sensitivity threshold may eliminate this inappropriate sensing.

Recommended ventricular sensitivity threshold – A ventricular sensitivity threshold of 0.3 mV is recommended to maximize the probability of detecting VF and to limit the possibility of oversensing and cross-chamber sensing.

High ventricular sensitivity threshold – Setting V. Sensitivity to a value greater than 0.6 mV is not recommended except for testing. Doing this may cause undersensing, which can cause any of the following situations:

delayed or aborted cardioversion therapy

•

delayed defibrillation therapy (when VF confirmation is

•

active)

asynchronous pacing

•

underdetection of tachyarrhythmias

•

Low ventricular sensitivity threshold – If you set V. Sensitivity to its most sensitive value of 0.15 mV, the device will be more susceptible to EMI, cross-chamber sensing, and oversensing.

Recommended atrial sensitivity threshold – An atrial sensitivity threshold of 0.3 mV is recommended to optimize the effectiveness of PR Logic detection criteria and atrial pacing operations, while limiting the possibility of oversensing and cross-chamber sensing.

High atrial sensitivity threshold – If you set the A. Sensitivity value too high, the device may not provide reliable sensing of P-waves during SVTs and sinus rhythm.

Low atrial sensitivity threshold – If you set the A. Sensitivity value to its most sensitive value of 0.15 mV, the device will be more susceptible to EMI, far-field R-wave sensing, and oversensing.

Testing sensitivity after reprogramming – If you change the ventricular sensitivity threshold, evaluate for proper sensing and detection by inducing VF and allowing the device to automatically detect and treat the arrhythmia.

INSYNC MAXIMO™7304 Reference Manual

Atrial pacing and ventricular sensing – If you program the

device to an atrial pacing mode, make sure that it does not sense atrial pacing pulses as ventricular events.

Sensing during VF – Always verify that the device senses properly during VF. If the device is not sensing or detecting properly, program detection and therapies off, and evaluate the system (making sure to monitor the patient for life-threatening arrhythmias until you enable detection and therapies again). You may need to reposition or replace the ventricular sensing lead to achieve proper sensing.

Atrial lead selection – Atrial leads with minimal tip-to-ring spacing may reduce far-field R-wave sensing.

Repositioning the atrial lead – You may need to reposition or replace the atrial sensing lead if reprogramming the atrial sensitivity threshold does not provide reliable atrial sensing during SVTs and sinus rhythm.

6.2.3 How to program sensitivity

6Detecting tachyarrhythmias

Setting up sensing

1. Select Params > Detection.

2. Select the desired A. Sensitivity and V. Sensitivity parameters.

3. Select [PROGRAM].

INSYNC MAXIMO™7304 Reference Manual

A P

V S

A S

V S

A S

V P

Sensitivity Threshold

Rectified and

Filtered A. EGM

Rectified and

Filtered RV EGM

Marker Channel

Chapter 6

Setting up sensing

6.2.4 Details about sensing

6.2.4.1 Auto-adjusting sensitivity thresholds

The device automatically adjusts the sensitivity thresholds after certain paced and sensed events to help reduce oversensing from T-waves, cross-chamber events, and pacing. You can see how sensitivity thresholds are adjusted after different types of events (see Figure 6-2).

Figure 6-2. Auto-adjusting sensitivity thresholds

1 After an atrial sensed event, the atrial sensitivity threshold increases

to 75% of the EGM peak (maximum: 8x the programmed value, decay constant: 200 ms).

2 After a ventricular sensed event, the ventricular sensitivity threshold

increases to 75% of the EGM peak (maximum: 8x the programmed value, decay constant: 450 ms).

3 After an atrial paced event, the device does not adjust the atrial

sensitivity threshold. The ventricular sensitivity threshold increases by 0.45 mV (decay constant: 60 ms).

4 After a ventricular paced event, the atrial sensitivity threshold

increases to 4x the programmed value (maximum: 1.8 mV, immediate return after 60 ms).

5 After the ventricular pace blanking period is finished, the ventricular

threshold increases to 4.5x the programmed value (maximum:

1.8 mV, decay constant: 450 ms).

The exponential decay continues through a subsequent ventricular pacing pulse and its blanking period.

INSYNC MAXIMO™7304 Reference Manual

6Detecting tachyarrhythmias

Setting up sensing

6.2.4.2 Blanking periods

During a blanking period, the device does not sense electrical signals. This helps prevent sensing of device pacing, cardioversion and defibrillation pulses, post-pacing depolarization, T-waves, and multiple sensing of the same event. The blanking periods following paced events are longer than those following sensed events to avoid sensing the atrial and ventricular depolarizations.

Notes:

To enhance sensing and detection during tachyarrhythmias,

•

the device does not apply cross-chamber blanking (blank sensing in the opposite chamber) after a sensed event.

Atrial sensing is still active during the Post-Ventricular

•

Atrial Blanking (PVAB) period (see Section 8.2.3.5, “Post-Ventricular Atrial Refractory Period”, page 160).

The duration of the fixed blanking periods is shown in Table 6-1. For information on programmable pace blanking periods, see Section 8.1, “Providing basic pacing therapy”, page 146.

Table 6-1. Duration of fixed blanking periods

Cross-chamber blanking after atrial or ventricular pacing pulse

Atrial blanking after sensed atrial event

Ventricular blanking after sensed ventricular event

Atrial and ventricular blanking after delivered cardioversion or defibrillation therapy

30 ms

100 ms

120 ms

520 ms

6.2.4.3 Refractory periods

During a refractory period, the device senses normally, but classifies sensed events as refractory and limits its response to these events. Pacing refractory periods prevent inappropriately sensed signals, such as far-field R-waves (ventricular events sensed in the atrium) or electrical noise, from triggering certain pacing timing intervals.

If the programmed sensitivity value exceeds 0.3 mV (ventricular) or 1.2 mV (atrial), the threshold is not adjusted.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detecting VF episodes

Synchronization refractory periods help prevent the device from delivering cardioversion and defibrillation therapies at inappropriate times. See Section 7.1.5.5, “Synchronizing defibrillation without confirming VF”, page 116, and Section 7.3.5.6, “Synchronizing cardioversion after charging”, page 136.

Note: Refractory periods do not affect tachyarrhythmia detection.

6.3 Detecting VF episodes

The device detects VF episodes by examining the cardiac rhythm for short ventricular intervals. If a predetermined number of intervals occurs that are short enough to be considered VF events, the device detects VF and delivers the first programmed VF therapy. After therapy, the device continues to evaluate the ventricular rhythm to determine if the episode is ongoing.

See Section 6.3.5, “Details about VF detection”, page 78.

6.3.1 Parameters

VF Detection Enable – Turns VF

detection on or off.

VF Interval (Rate) – V-V intervals shorter than this value are counted as VF events.

VF Initial NID – Number of Intervals to Detect: number of VF events the device must count to detect a VF episode.

VF Redetect NID – Number of Intervals to Redetect: number of VF events the device must count to redetect a continuing VF after a therapy.

6.3.2 Considerations

Review the following information before programming VF Detection parameters.

VF Interval minimum setting – To ensure proper VF detection, you should not program the VF Interval to a value less than 300 ms.

INSYNC MAXIMO™7304 Reference Manual

; Off

240; 250 … 320 400 ms

12/16; 18/24 30/40; 45/60; 60/80; 75/100; 90/120; 105/140; 120/160

6/8; 9/12; 12/16 21/28; 24/32; 27/36; 30/40

…

; 24/32;

; 18/24;

6Detecting tachyarrhythmias

Detecting VF episodes

VF Interval maximum setting – Programming the VF Interval to a value greater than 350 ms may cause inappropriate detection of rapidly conducted atrial fibrillation as VF or FVT via VF. Intervals shorter than the VF Interval are counted using the VF event counter, which is more sensitive than the consecutive VT event counter.

VF, FVT, and VT Intervals – To allow for normal variations in the patient’s tachycardia interval, you should program the VF, FVT, and VT intervals at least 40 ms apart.

Episode redetection – You can expedite redetection by programming the VF and VT Redetect NIDs lower than the Initial NIDs.

Enabling VF detection – When VF Detection Enable is programmed On for the first time, the device:

enables Automatic Capacitor Formation

•

starts recording Cardiac Compass data and Heart Failure

•

Management data

starts recording lead performance trends (starting at

•

3:00 AM by the device clock)

clears all brady pacing counters

•

VF detection and PR Logic criteria – You can program the device to exclude rapidly conducted SVTs from VF Detection by enabling the PR Logic detection criteria. Note that the SVT Limit must be programmed shorter than the VF Interval in order for the PR Logic criteria to affect VF detection. See Section 6.8, “Enhancing detection with PR Logic criteria”, page 96.

6.3.3 Restrictions

Double tachycardia detection – When any PR Logic detection

criteria are enabled, the device also enables double tachycardia detection (VF, VT, or FVT in the presence of an SVT). See Section 6.10, “Detecting double tachycardias”, page 106.

Review the following information before programming VF Detection parameters.

Tachyarrhythmia detection and pacing – To ensure reliable ventricular tachyarrhythmia detection, the programmer regulates the values available for pacing and tachyarrhythmia detection. See Section B.11, “Parameter interlocks”, page 388.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detecting VF episodes

VF detection backup – To ensure VF Detection backup during VT and FVT episodes, if VF Detection is off, both VT Detection and FVT Detection must also be off.

6.3.4 How to program VF detection

1. Select Params > Detection.

2. Select the desired values for VF Enable, VF Initial NID, VF Redetect NID, and VF Interval.

3. Select [PROGRAM].

6.3.5 Details about VF detection

The device detects VF by counting the number of VF events, which are V-V intervals shorter than the programmed VF Interval. On each event, the device counts the number of recent VF events. The number of recent events that are examined is called the VF detection window. The size of the VF detection window is the second number in the programmed VF NID (for example, 24 events if the VF Initial NID is 18/24).

The threshold for detecting VF is the first number in the programmed VF NID (for example, 18 events if the VF Initial NID is 18/24). This threshold is always 75% of the VF detection window. That is, if 75% of the events in the VF detection window are VF events, the device detects a VF episode (see Figure 6-3).

After the device detects VF, it delivers the first programmed VF therapy. Following the therapy, if the number of VF events reaches the programmed VF Redetect NID, the device redetects

INSYNC MAXIMO™7304 Reference Manual

VF and delivers the next programmed VF therapy.

Note: The device can also detect VF Episodes using the Combined Count detection criterion (see Section 6.6, page 90).

Figure 6-3. Device detects VF

A S

V S

A R

1 2 3 4 5 6 6 7 8 9 10 11 12 13 1415 16 17 18

F S

F D

200 ms

VF Event Count

ECG

Marker Channel

VF Interval

1 VF starts, and the device begins counting VF events (intervals less

than the programmed VF Interval).

2 A ventricular interval occurs outside the VF detection zone. The VF

event count is not incremented.

3 The VF event count reaches the programmed VF NID value of 18

events out of 24, and the device detects VF.

6Detecting tachyarrhythmias

Detecting VT episodes

6.4 Detecting VT episodes

The device detects VT episodes by examining the cardiac rhythm for short ventricular intervals. If enough intervals occur that are short enough to be considered VT events (but are not VF or FVT events), the device detects VT and delivers the first programmed VT therapy. After therapy, the device continues to evaluate the ventricular rhythm to determine if the episode is ongoing.

You can program the device to detect and record VT episodes without treating them with VT therapies by setting VT Detection Enable to Monitor. If a patient’s VT episodes are well-tolerated, this feature allows you to collect data about these episodes without delivering therapy or affecting VF detection.

See Section 6.4.5, “Details about VT detection”, page 81.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detecting VT episodes

6.4.1 Parameters

VT Detection Enable – Turns VT

detection on or off, or enables VT monitoring.

VT Interval (Rate) – V-V intervals shorter than this value are counted as VT events.

VT Initial NID – Number of Intervals to Detect: number of VT events the device must count to detect a VT episode.

VT Redetect NID – Number of Intervals to Redetect: number of VT events the device must count to redetect a continuing VT after a therapy.

6.4.2 Considerations

Review the following information before programming VT Detection parameters.

VF, FVT, and VT Intervals – To allow for normal variations in the patient’s tachycardia interval, you should program the VF, FVT, and VT intervals at least 40 ms apart.

Episode redetection – You can expedite redetection by programming the VF and VT Redetect NIDs lower than the Initial NIDs.

On; Off

280; 290 … 400

12; 16

4; 8; 12

; or Monitor

…52; 76; 100

… 52

… 600 ms

VT Detection Enable, AFib/AFlutter, and Sinus Tach – When you set VT Detection Enable to On or Monitor, the AFib/AFlutter and Sinus Tach parameters are also automatically set to On.

VT detection and Combined Count detection – When VT Detection is On, the device applies the Combined Count detection criterion to help speed detection of rhythms that fluctuate between detection zones. Combined Count detection is disabled if VT Detection is set to Off or Monitor. See Section 6.6, “Detecting tachyarrhythmia episodes with Combined Count”, page 90.

VT detection and rapidly conducted SVTs – You can program the device to exclude rapidly conducted SVTs from VT detection by enabling the PR Logic or Stability detection criteria. See Section 6.9, “Enhancing VT detection with the Stability criterion”, page 104, and Section 6.8, “Enhancing detection with PR Logic criteria”, page 96.

INSYNC MAXIMO™7304 Reference Manual

Double tachycardia detection – When any PR Logic detection

criteria are enabled, the device also enables double tachycardia detection (VF, VT, or FVT in the presence of an SVT; see Section 6.10, page 106).

6.4.3 Restrictions

Review the following information before programming VT detection parameters.

VF detection backup – To ensure VF detection backup during VT and FVT episodes, if VF Detection is off, both VT Detection and FVT Detection must also be off.

6.4.4 How to program VT detection

6Detecting tachyarrhythmias

Detecting VT episodes

1. Select Params > Detection.

2. Select the desired values for VT Enable, VT Initial NID, VT Redetect NID, and VT Interval.

3. Select [PROGRAM].

6.4.5 Details about VT detection

The device detects VT by counting the number of consecutive VT events. A VT event is a V-V interval shorter than the programmed VT Interval but greater than or equal to the VF Interval. If the number of consecutive VT events reaches the programmed VT Initial NID, the device detects VT (see Figure 6-4).

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detecting VT episodes

The VT event count resets to zero whenever an interval occurs that is greater than or equal to the programmed VT Interval. The count remains at the current value if an interval is shorter than the programmed VF Interval.

After the device detects VT, it delivers the first programmed VT therapy. Following the therapy, if the VT event counter reaches the VT Redetect NID, the device redetects VT and delivers the next programmed therapy.

Note: The device can also detect VT Episodes using the Combined Count detection criterion (see Section 6.6, page 90).

INSYNC MAXIMO™7304 Reference Manual

Figure 6-4. Device detects VT

A S

V S

A R

1 0 1 2 3 4 5 6

T S

V S

A R

7 8 9 10 11 12 13 14 15 16

T S

T D

VT Event Count

ECG

Marker Channel

VT Interval

VT Event Count

ECG

Marker Channel

VT Interval

6Detecting tachyarrhythmias

Detecting VT episodes

1 VT starts, and the device begins counting VT events (intervals less

than the programmed VT Interval but greater than or equal to the VF Interval).

2 A ventricular interval occurs outside VT detection zone. The VT event

count resets to zero.

3 The VT event count reaches the programmed VT NID of 16 events,

and the device detects VT.

6.4.5.1 VT monitoring

You can program the device to record VT episodes without delivering VT therapy by setting VT Detection to Monitor. When VT monitoring is enabled, the device detects VT episodes but does not deliver VT therapy (see Figure 6-5). Instead, it records VT episodes, labeling them as “monitored,” and waits for episode termination to occur.

When VT Detection is set to Monitor, several detection operations work differently.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detecting VT episodes

VT event counting – Before the device detects an episode, it counts VT events normally. However, once the VT Initial NID is reached, the device sets the VT event count to zero and suspends VT event counting for the rest of the episode.

VF and FVT detection – VF and FVT detection operate as if VT detection is off. Specifically, Combined Count detection is disabled, and FVT via VT detection is not selectable. If a monitored VT episode accelerates into the FVT or VF detection zone, the device applies the VF Initial NID to detect the new tachyarrhythmia. Once an episode is in progress, VT event counting doesn’t resume until the episode ends.

Caution: Programming the VF Interval greater than 350 ms may result in inappropriate detection of rapidly conducted atrial fibrillation as VF or FVT via VF. Intervals shorter than the VF Interval are counted using the VF event counter, which is more sensitive than the consecutive VT event counter.

PR Logic and Stability criteria – Before the device detects a tachyarrhythmia episode, the PR Logic and Stability criteria, if turned on, are applied. If a monitored VT episode accelerates into the FVT or VF detection zone, the device continues to apply PR Logic criteria as initial VF or FVT detection begins. However, because the Stability feature does not affect VF detection or FVT via VF detection, it is not applied.

Episode termination – The device compares ventricular intervals to the VT Interval to identify when a VT monitored episode has ended. However, if a VF episode or FVT via VF episode occurs when VT monitoring is enabled, the device compares ventricular intervals to the VF Interval to identify episode termination.

INSYNC MAXIMO™7304 Reference Manual

Figure 6-5. Device detects and monitors VT

200 ms

1 2 3 4

A S

A R

A RA RA

V S

V ST ST ST ST

13 14 15 16 0 0 0

A R

A RA RA RA RA

T ST ST ST DT ST ST

VT Event Count

ECG

Marker Channel

VT Interval

1 VT starts, and the device begins counting VT events (intervals less

than the programmed VT Interval but greater than or equal to the VF Interval).

2 The VT event count reaches the programmed VT NID of 16 events,

and the device detects VT.

3 After detecting the VT episode, the device resets the VT event count

to zero and monitors the episode until termination.

6Detecting tachyarrhythmias

Detecting FVT episodes

6.5 Detecting FVT episodes

The device detects episodes of Fast Ventricular Tachycardia (FVT) by examining the cardiac rhythm for short ventricular intervals. If enough intervals occur in the programmed FVT detection zone, the device detects FVT and delivers the first programmed FVT therapy. After therapy, the device continues to evaluate the ventricular rhythm to determine if the episode is ongoing. To make sure it delivers sufficiently aggressive therapies, the device can merge the programmed detection zones during redetection to increase sensitivity.

See Section 6.5.5, “Details about FVT detection”, page 88.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detecting FVT episodes

6.5.1 Parameters

FVT Detection Enable – Enables FVT

detection via the VF or the VT detection algorithm.

FVT Interval (Rate) – V-V intervals between this value and the programmed VF Interval are marked as FVT events.

6.5.2 Considerations

Review the following information before programming FVT Detection parameters.

VF, FVT, and VT Intervals – To allow for normal variations in the patient’s tachycardia interval, you should program the VF, FVT, and VT intervals at least 40 ms apart.

Episode redetection – You can expedite redetection by programming the VF and VT Redetect NIDs lower than the Initial NIDs.

FVT detection enable – Your choice for an appropriate setting for FVT Detection should depend on the patient’s VF and VT cycle lengths. After determining a reliably sensitive VF Interval, consider the following suggestions:

•

; via VF; or via

Off VT

200; 210 … 600 ms

If the patient presents with a clinical VT interval in the VF zone, select via VF to ensure reliable detection of VF. (VT Detection need not be enabled at all.)

If the patient presents with 2 clinical VTs, both outside the

•

VF zone, select via VT to allow for correct classification of the faster VT and to offer a separate therapy regimen for each VT.

If the patient presents with only 1 clinical VT, which is outside

•

the VF zone, select VF and VT Detection only, and set FVT Enable to Off.

FVT detection and PR Logic criteria – You can program the device to exclude rapidly conducted SVTs from FVT Detection by enabling the PR Logic detection criteria. Note that the SVT Limit must be programmed shorter than the VF Interval for the PR Logic criteria to affect FVT via VF detection.

INSYNC MAXIMO™7304 Reference Manual

6.5.3 Restrictions

6Detecting tachyarrhythmias

Detecting FVT episodes

Double tachycardia detection – When any PR Logic detection criterion is enabled, the device also enables double tachycardia detection (VF, VT, or FVT in the presence of an SVT, see Section 6.10, page 106).

Review the following information before programming FVT Detection parameters.

Tachyarrhythmia detection and bradycardia pacing – To ensure reliable ventricular tachyarrhythmia detection, the programmer regulates the values available for bradycardia pacing and tachyarrhythmia detection. See Section B.11, “Parameter interlocks”, page 388.

VF detection backup – To ensure VF Detection backup during VT and FVT episodes, VT and FVT Detection cannot be on unless VF Detection is also on.

FVT detection – To ensure reliable ventricular tachyarrhythmia detection, the programmer regulates the values available for the FVT parameter as follows:

VT Detection must be set to On if FVT Detection is set to

•

via VT.

If FVT Detection is set to via VF, the FVT Interval must be

•

programmed to a value shorter than the VF Interval.

If FVT Detection is set to via VT, the FVT Interval must be

•

programmed to a value greater than the VF Interval and less than or equal to the VT Interval.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Detecting FVT episodes

6.5.4 How to program FVT detection

6.5.5 Details about FVT detection

You can program the device to detect FVT episodes via the VF or VT detection zone and NID.

1. Select Params > Detection.

2. Select the desired values for FVT Enable and FVT Interval.

3. Select [PROGRAM].

When FVT Detection is set to via VF, a V-V interval within the FVT detection zone is marked as an “FVT via VF” event. When the VF NID is reached, the device reviews the last 8 intervals:

If any of the last 8 intervals are in the VF zone, it detects

•

the episode as VF.

If all of the last 8 intervals are outside the VF zone, it detects

•

the episode as FVT (see Figure 6-6).

When FVT Detection is set to via VT, a V-V interval within the FVT detection zone is marked as an “FVT via VT” event. When the VT NID is reached, the device reviews the last 8 intervals:

If any of the last 8 intervals are in the VF or FVT zones, it

•

detects the episode as FVT.

If all of the last 8 intervals are outside the FVT and VF zones,

•

it detects the episode as VT.

Note: The device can also detect FVT episodes via the Combined

INSYNC MAXIMO™7304 Reference Manual

Count detection criterion (see Section 6.6, page 90).

Figure 6-6. Device detects FVT via VF

200 ms

13 14 15 16 17 18

A RA RA RA RA RA RA RA RA

T FT

T F

T FV

1 1 2 3 4 5

A S

A RA RA

A R

V S

T S

T F

VF Event Count

ECG

Marker Channel

VF and FVT Intervals

1 A fast ventricular tachycardia starts, and the first event falls into the

FVT detection zone.

2 The second event of the FVT episode has an interval that falls into

the VT zone. The VF event count is not incremented.

3 The device detects FVT after the VF event count reaches the VF

Initial NID.

6Detecting tachyarrhythmias

Detecting FVT episodes

6.5.5.1 Zone merging after detection

To ensure that the device delivers sufficiently aggressive therapies during an extended or highly variable tachyarrhythmia episode, the device merges detection zones during redetection in some instances, as shown in Figure 6-7. The merged zone configuration uses the event counting and therapies for the faster arrhythmia and remains in effect until episode termination.

INSYNC MAXIMO™7304 Reference Manual

Before detection

After VF detection

After FVT detection

FVT set to “via VF”

VF and FVT zones merge, leaving a larger VF zone.

All zones remain unchanged.

FVT set to “via VT”

VT and FVT zones merge, leaving a larger FVT zone.

Detection Intervals: VF Interval: 320 ms, FVT Interval: 280 ms / 360 ms, VT Interval: 400 ms

FVT

Chapter 6

Detecting tachyarrhythmia episodes with Combined Count

Figure 6-7. FVT zone merging

6.6 Detecting tachyarrhythmia episodes with Combined Count

INSYNC MAXIMO™7304 Reference Manual

Because the device counts VF and VT events separately, rhythms with variable cycle lengths can cause both event counts to increment during an episode. To prevent these rhythms from delaying detection, the device automatically enables the Combined Count detection criterion if both VF and VT detection are programmed On.

The Combined Count criterion compares the sum of the VF and VT event counts to the Combined Number of Intervals to Detect (CNID), which the device calculates automatically from the programmed VF NID values. If the CNID is met, the device reviews the recent intervals to determine if the episode should be treated as a VF, FVT, or VT episode. The Combined Count criterion applies during both initial detection and redetection.

Detecting tachyarrhythmia episodes with Combined Count

6.6.1 Details about Combined Count detection

The Combined Count detection algorithm expedites detection or redetection of ventricular tachyarrhythmias with ventricular intervals that fluctuate between the VF and VT detection zones. When VT detection is on, the device applies Combined Count detection, which tracks the combined number of VT and VF events counted. If this sum reaches the Combined Number of Intervals to Detect (CNID), the device detects VF, FVT, or VT. Combined Count detection also applies to redetected episodes.

Note: Combined Count detection is off when VT detection is set to Monitor or Off.

If the VF event counter reaches 6, the device automatically applies the Combined Number of Intervals to Detect (CNID). The CNID is calculated by multiplying the current VF NID (Initial or Redetect) by 7/6 and rounding down. Table 6-2 shows the CNID values that correspond to each VF NID value.

Table 6-2. CNID values for each initial or redetect VF NID value

VF NID CNID VF NID CNID

6/8

9/12

12/16

18/24

6Detecting tachyarrhythmias

21/28

24/32

27/36

30/40

Combined Count detection is fulfilled when the sum of the VF and VT event counts equals or exceeds the CNID. The device then reviews the last 8 intervals and classifies the episode as one of the following:

VF, if any of the last 8 were in the VF zone

•

FVT, if FVT Detection is enabled and none of the last 8 was

•

in the VF zone, but one or more was in the FVT zone

VT, if all 8 were outside the VF zone (and FVT zone, if FVT

•

detection is enabled)

INSYNC MAXIMO™7304 Reference Manual

200 ms

A SA RA RA RA RA RA RA RA RA RA RA RA

A RA RA RA RA RA RA RA

A R

V SV SF

F S

F SF SF SF SF SF ST SF SF SF SF SF SF SF SF

F S

T ST

F DV

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

1 2 3 4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

VF Event Count

VT Event Count

Combined Count

VF and VT Interval

ECG

Marker Channel

Chapter 6

Monitoring episodes for termination or redetection

Figure 6-8. Device detects VF with the Combined Count criterion

1 A slow VF episode starts with a ventricular cycle length that varies

between the VF and VT detection zones.

2 When a VT event occurs, the device increments the VT event count

and the Combined Count.

3 The device detects VF even though the VF event count hasn’t yet

reached the VF Initial NID (18/24 in this example). The Combined Count reaches the CNID value of 21 first.

6.7 Monitoring episodes for termination or redetection

Once the device detects an arrhythmia, it considers the episode

INSYNC MAXIMO™7304 Reference Manual

ongoing until it detects that the episode has ended. After delivering therapy, it monitors the ventricular rhythm using the programmed Redetect NIDs. If one of these NIDs is met, the device delivers the next programmed therapy for the detected arrhythmia.

See Section 6.7.4, “Details about episode termination and redetection”, page 93.

6.7.1 Parameters

6Detecting tachyarrhythmias

Monitoring episodes for termination or redetection

VF Redetect NID – Number of Intervals to Redetect: number of VF events the device must count to redetect a continuing VF after a therapy.

VT Redetect NID – Number of Intervals to Redetect: number of VT events the device must count to redetect a continuing VT after a therapy.

6.7.2 Considerations

Review the following information before programming redetection parameters.

Initial and Redetect NIDs – You can expedite redetection by programming the VF and VT Redetect NIDs lower than the Initial NIDs.

6.7.3 How to program redetection parameters

6/8; 9/12; 12/16 21/28; 24/32; 27/36; 30/40

4; 8; 12

1. Select Params > Detection.

2. Select the desired values for VT Redetect NID and VF Redetect NID.

3. Select [PROGRAM].

… 52

; 18/24;

6.7.4 Details about episode termination and redetection

After a therapy is delivered, the device evaluates the ventricular rhythm to determine if the episode has terminated, is continuing, or has changed to a different arrhythmia.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Monitoring episodes for termination or redetection

6.7.4.1 Episode termination

The device determines that the episode has terminated if one of the following conditions occurs:

8 consecutive ventricular intervals are greater than or equal

•

to the programmed VT interval.

20 s elapse with no ventricular intervals shorter than the

•

programmed VT interval.

After antitachycardia pacing therapy, the device begins evaluating intervals for episode termination on the first ventricular cycle. After cardioversion or defibrillation, the device begins evaluating intervals for episode termination on the second ventricular event. (Due to the extended post shock blanking, this event may be the

third event on the electrogram.)

Note: Any subsequent detection after the end of the episode

marks the start of a new episode.

6.7.4.2 Episode redetection

After the device detects a tachyarrhythmia episode and delivers a therapy, the device redetects an arrhythmia if the VF or VT event count reaches the Redetect NID or if the combined VF and VT event count reaches the Redetect CNID (see Section 6.6, “Detecting tachyarrhythmia episodes with Combined Count”, page 90).

The device then delivers the next programmed therapy for the current arrhythmia and resumes monitoring for the outcome of that therapy (see Figure 6-9).

VF interval if VT Detection is set to Off or Monitor and the episode is a VF or an FVT via VF episode.

INSYNC MAXIMO™7304 Reference Manual

Monitoring episodes for termination or redetection

A RA SA SA SA SA SA RA RA RA RA RA RA RA RA RA RA RA RA

T P

T PT

T PT DT PT PT PT PT PT ST ST ST ST ST ST ST ST ST ST ST

200 ms

016 0 1 2 3 4 5 6 7 8 9 10 11 12

VT Event Count

ECG

Marker Channel

VT Interval

Figure 6-9. VT episode redetected after therapy

1 A VT episode is detected, and the device delivers a Burst ATP therapy. 2 After therapy, the device continues to detect events in the VT zone. 3 When the VT event count reaches the VT Redetect NID, the device

redetects the VT.

Notes:

The device suspends VT detection (and Combined Count

•

detection) for 17 events following a defibrillation therapy delivered in response to a detected VF. detection helps avoid detecting transient VTs that can follow high-voltage therapies.

The PR Logic criteria are not applied during redetection.

•

However, the Stability criterion may withhold detection or redetection of VT (or FVT via VT) throughout an episode.

6Detecting tachyarrhythmias

Suspending VT

6.7.4.3 VT acceleration

If the device redetects VT, it classifies the rhythm as accelerated if the average of the 4 intervals before redetection is at least 60 ms less than the average of the 4 intervals before initial VT detection. The most recent interval average is used to identify VT acceleration if VT is redetected again during the episode.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Enhancing detection with PR Logic criteria

If the device redetects VF or an accelerated VT after an antitachycardia pacing sequence delivery, it skips the subsequent pacing therapy sequences for the duration of the episode and delivers the next therapy programmed for the current arrhythmia.

6.8 Enhancing detection with PR Logic criteria

The PR Logic detection criteria are designed to withhold inappropriate ventricular detection during episodes of rapidly conducted supraventricular tachycardia (SVT). The device analyzes the activation patterns and timing in both chambers using PR Logic pattern and rate analysis. This information helps identify evidence of atrial fibrillation, atrial flutter, sinus tachycardia, and other 1:1 SVTs. If this analysis indicates the presence of one or more of these rhythms, the device withholds detection.

For more information, see

Section 6.8.5, “Details about PR Logic pattern and rate

•

analysis”, page 99

Section 6.8.6, “Details about the PR Logic detection

•

criteria”, page 103

6.8.1 Parameters

AFib/AFlutter – Identifies rapidly conducted

atrial fibrillation, atrial flutter, or atrial tachycardia

Sinus Tach – Identifies sinus tachycardia

1:1 VT-ST Boundary – Allows customizing

of the Sinus Tach criterion for patients with slow one-to-one conduction by identifying the threshold between the retrograde and antegrade zones used by A-V pattern analysis.

Other 1:1 SVTs – Identifies other one-to-one SVTs where the atrial and ventricular activation are roughly simultaneous

SVT Limit – Defines the minimum ventricular interval at which the device applies the PR Logic criteria

When you set VT Detection Enable to On or Monitor, the AFib/AFlutter and Sinus Tach parameters are also automatically set to On.

INSYNC MAXIMO™7304 Reference Manual

Ona; Off

35; 50

On; Off

240; 250 … 320 330; 340 … 600 ms

; 66; 75; 85%

;

6.8.2 Considerations

Review the following information before programming PR Logic parameters.

PR Logic criteria and double tachycardia detection – When any of the PR Logic criteria are enabled, the device also enables double tachycardia detection (VF, VT, or FVT in the presence of an SVT; see Section 6.10.1, page 106).

6Detecting tachyarrhythmias

Enhancing detection with PR Logic criteria

Cautions:

Before enabling the Other 1:1 SVTs criterion, ensure

•

that the atrial lead has matured. This criterion could inappropriately withhold therapy if atrial sensing is compromised by an unstable or dislodged atrial lead.

Use caution when programming the Other 1:1 SVTs

•

criterion in patients who exhibit slow 1:1 retrograde conduction during VF or VT. This criterion could inappropriately withhold VF/VT therapy in such patients. See Section 6.8.5.1, “Pattern analysis of A-V and V-A intervals”, page 100.

Use caution when programming the 1:1 VT-ST

•

Boundary. Incorrect programming of this parameter can result in inappropriate therapies or underdetection of tachyarrhythmias.

Sinus Tach and 1:1 VT-ST Boundary – When enabling the Sinus Tach criterion in patients who exhibit slow 1:1 retrograde conduction during VF or VT or slow antegrade conduction during SVTs, make sure to set the 1:1 VT-ST Boundary parameter appropriately. See Section 6.8.2.1, “Customizing PR Logic for patients with slow conduction”, page 98.

VT Detection Enable, AFib/AFlutter and Sinus Tach – When you set VT Detection Enable to On or Monitor, the AFib/AFlutter and Sinus Tach parameters also automatically set to On.

SVT Limit – To ensure that therapy is delivered for hemodynamically compromising rates of any origin, the device always delivers therapy when the median ventricular interval is less than the programmed SVT Limit (nominally 320 ms) if VT, VF, or FVT detection criteria are satisfied.

VF Interval and SVT Limit – If you program an SVT Limit greater than the VF Interval, you are effectively disabling the PR Logic criteria for VF detection.

INSYNC MAXIMO™7304 Reference Manual

Chapter 6

Enhancing detection with PR Logic criteria

6.8.2.1 Customizing PR Logic for patients with slow conduction

Slow antegrade conduction during an SVT or slow 1:1 retrograde conduction during VT can adversely affect the accuracy of the Sinus Tach and Other 1:1 SVTs criteria. The 1:1 VT-ST Boundary parameter allows you to customize the Sinus Tach criterion for patients who exhibit slow conduction.

Note: Changing the 1:1 VT-ST Boundary parameter does not affect the operation of the Other 1:1 SVTs criterion. Use caution when enabling this criterion in patients who exhibit slow antegrade or retrograde conduction.

The 1:1 VT-ST Boundary parameter represents an A-V interval that is a percentage of a V-V interval. This value separates the retrograde and antegrade zones used by PR Logic pattern analysis operations. See Section 6.8.5.1, “Pattern analysis of A-V and V-A intervals”, page 100.

If slow retrograde or antegrade conduction causes events to occur in the incorrect zone, you can use the 1:1 VT-ST Boundary parameter to increase the size of the appropriate zone. See Figure 6-10, page 100.

If a patient exhibits slow antegrade or retrograde conduction and could benefit from a different 1:1 VT-ST Boundary setting, choose a new setting as follows:

If the patient exhibits long V-A intervals during VT with 1:1

•

retrograde conduction, select 35%.

If the patient exhibits long A-V intervals during an SVT,

•

select a value that exceeds the A-V/V-V ratio observed during stored VT/VF or SVT episodes. See Section 12.7.3.1, page 297.

6.8.3 Restrictions

Review the following information before programming PR Logic parameters.

Sinus Tach and 1:1 VT-ST Boundary – The Sinus Tach criterion must be on before 1:1 VT-ST Boundary can be selected.

VT Detection Enable and SVT Limit – The SVT Limit must be shorter than the VT Interval (or VF Interval if VT Detection is off).

INSYNC MAXIMO™7304 Reference Manual

6Detecting tachyarrhythmias

Enhancing detection with PR Logic criteria

6.8.4 How to program the PR Logic detection criteria

1. Select Params > Detection.

2. Select the desired values for AFib/AFlutter, Sinus Tach, Other 1:1 SVTs, and SVT Limit.

3. If you need to adjust the 1:1 VT-ST Boundary for your patient, select Additional Settings….

4. Select the desired value for the 1:1 VT-ST Boundary.

5. Select [OK].

6. Select [PROGRAM].

6.8.5 Details about PR Logic pattern and rate analysis

PR Logic pattern and rate analysis is based on the following aspects of atrial and ventricular activation:

A-V and V-A interval patterns

•

atrial and ventricular rate

•

AF evidence

•

far-field R-wave sensing

•

A:V dissociation

•

V-V regularity

•

The information collected by PR Logic pattern and rate analysis is used by the PR Logic detection criteria to identify the presence of SVTs and withhold detection.

INSYNC MAXIMO™7304 Reference Manual

100

85%

75%

66%

35%

Chapter 6

Enhancing detection with PR Logic criteria

6.8.5.1 Pattern analysis of A-V and V-A intervals

The device uses pattern analysis to identify sinus tachycardia, atrial flutter, and other 1:1 SVTs. Within each V-V interval, the device categorizes the atrial rhythm according to the number of intervening atrial events and the zones in which those atrial events occur (see Figure 6-10). From this information, the device assigns pattern codes to the intervals, and interprets the pattern codes to identify SVTs.

Figure 6-10. Zones used during A-V pattern analysis

1 Junctional Zone: 50 ms. Atrial events in the first junctional zone

indicate PAC, PVC, junctional rhythms, atrial fibrillation, or atrial flutter.

2 Retrograde Zone. Atrial events in the retrograde zone indicate

retrograde conduction of ventricular events.

3 The 1:1 VT-ST Boundary separates the retrograde and antegrade

zones. The nominal value of this boundary is 50%.

4 Antegrade (Normal) Zone. Atrial events in the antegrade zone

INSYNC MAXIMO™7304 Reference Manual

indicate normal conduction (sinus rhythm, sinus tachycardia).

5 Junctional Zone: 80 ms. Atrial events in the second junctional zone

indicate PAC, PVC, junctional rhythms, atrial fibrillation, or atrial flutter.

6 The 1:1 VT-ST Boundary can be programmed to different values,

changing the relative size of the antegrade and retrograde zones.

Medtronic 7304 Reference Guide

Specifications and Main Features

Frequently Asked Questions

User Manual