Medtronic 7278 Reference Guide

MAXIMO™ DR 7278

Dual Chamber Implantable Cardioverter Defibrillator

Reference Manual

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

MaximoTM DR 7278 0

Reference Manual 0

A guide to the operation and programming of the Model 7278 MaximoTM DR Dual Chamber Implantable Cardioverter Defibrillator

The following are trademarks of Medtronic:

Active Can, Cardiac Compass, Checklist, Decision Channel, Flashback, GEM, Leadless ECG, Marker Channel, Maximo, Medtronic, Patient Alert, PR Logic, Quick Look, QuickLink, RapidRead, T-Shock

Introduction 11

Abbreviations and acronyms 13

Part I Quick overview

1 Quick reference 17

Physical characteristics 18

Magnet application 19

Longevity projections 19

Replacement indicators 22

Typical charge times 23

High voltage therapy energy 23

Stored data and diagnostics 25

New and enhanced features 27

2 The Maximo DR system 31

System overview 32

Indications and usage 35

Contraindications 35

Patient screening 35

3 Emergency therapy 37

Delivering emergency therapies 38

Part II Device implant and patient follow-up procedures

4 Implanting the ICD 47

Overview 48

Preparing for an implant 48

Replacing an ICD 50

Positioning the leads 51

Testing sensing and pacing thresholds 53

Connecting the leads to the ICD 54

Testing defibrillation operation and effectiveness 55

Positioning and securing the ICD 58

Maximo DR 7278 Reference Manual

Table of contents

Completing the implant procedure 59

5 Conducting a patient follow-up session 61

Patient follow-up guidelines 62

Verifying the status of the implanted system 62

Verifying accurate detection and appropriate therapy 63

Verifying effective bradycardia pacing 65

Part III Configuring the ICD for the patient

6 Detecting tachyarrhythmias 69

Detection overview 70

Setting up sensing 73

Detecting VF episodes 78

Detecting VT episodes 82

Detecting FVT episodes 88

Detecting tachyarrhythmia episodes with Combined Count 93

Monitoring episodes for termination or redetection 95

Enhancing detection with PR Logic criteria 98

Enhancing VT detection with the Stability criterion 108

Detecting double tachycardias 111

Detecting prolonged tachyarrhythmias with High Rate Timeout 112

Key terms 114

7 Treating tachyarrhythmia episodes 119

Treating VF with defibrillation 120

Treating VT and FVT with antitachycardia pacing 130

Treating VT and FVT with cardioversion 140

Optimizing therapy with Smart Mode and Progressive Episode Therapies 149

Key terms 153

8 Treating bradycardia 157

Providing basic pacing therapy 158

Dual-chamber pacing 164

Single chamber pacing 174

Enhancing pacing for optimal cardiac output 177

Maximo DR 7278 Reference Manual

Table of contents

Adjusting the pacing rate with Mode Switch 190

Preventing competitive atrial pacing 194

Detecting and preventing pacemaker-mediated tachycardia 199

Providing Ventricular Safety Pacing 203

Providing pacing after high voltage therapies 206

Key terms 208

9 Optimizing charge time and device longevity 213

Optimizing charge time 214

Optimizing device longevity 217

Key terms 218

Part IV Evaluating and managing patient treatment

10 Using the programmer 221

Setting up and using the programmer 222

Display screen features 223

Viewing and programming device parameters 230

Starting and ending patient sessions 234

Viewing live waveform traces 236

Recording live waveform strips 243

Saving and retrieving device data 245

Printing reports 249

Key terms 254

11 Using system evaluation tools 255

A summary of system evaluation tools 256

Taking a quick look at device activity 257

Using the Patient Alert feature 259

Streamlining follow-ups with Checklist 267

Key terms 270

12 Setting up and viewing collected data 271

A summary of data collection 272

Setting up data collection 273

Collecting lead performance data 278

Viewing the episode and therapy efficacy counters 279

Maximo DR 7278 Reference Manual

Table of contents

Viewing episode data 284

Viewing Flashback Memory 292

Viewing battery and lead status data 294

Viewing lead performance trends 296

Using Cardiac Compass to view long term clinical trends 298

Viewing and entering patient information 305

Automatic device status monitoring 308

Key terms 311

13 Testing the system 315

Testing overview 316

Evaluating the underlying rhythm 316

Measuring pacing thresholds 317

Measuring lead impedance 320

Measuring EGM Amplitude 322

Testing the device capacitors 324

Key terms 326

14 Conducting Electrophysiologic Studies 327

EP Study overview 328

Inducing VF with T-Shock 330

Inducing VF with 50 Hz Burst 334

Inducing an arrhythmia with Manual Burst 337

Inducing an arrhythmia with PES 340

Delivering a manual therapy 343

Key terms 346

15 Solving system problems 349

Overview 350

Solving sensing problems 351

Solving tachyarrhythmia detection problems 353

Solving tachyarrhythmia therapy problems 354

Solving bradycardia pacing problems 355

Responding to device status indicators 357

Key terms 358

Maximo DR 7278 Reference Manual

Part V Appendices

A Warning and precautions 363

General warnings 364

Storage and handling 364

Resterilization 365

Device implantation and ICD programming 365

Lead evaluation and lead connection 367

Follow-up testing 368

Explant and disposal 369

Medical therapy hazards 369

Home and occupational environments 371

BDevice parameters373

Emergency settings 374

Detection parameters 375

Therapy parameters 377

Bradycardia pacing parameters 379

System maintenance parameters 382

Data collection parameters 383

System test and EP study parameters 384

Fixed parameters 387

Patient information parameters 389

Programmer symbols 390

Parameter interlocks 392

Table of contents

Index 393

Maximo DR 7278 Reference Manual

Introduction

Using this manual

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

■

Refer to the product literature packaged with the ICD for information about prescribing the ICD.

■

Thoroughly read this manual and the technical manuals for the leads used with the device.

■

Discuss the procedure and the ICD system with the patient and any other interested parties, and provide them with any patient information packaged with the ICD.

Contacting technical support

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.

Introduction

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.

Customer education

Medtronic invites physicians to attend an education seminar on the complete ICD system. The course includes indications for use, an overview of ICD system functions, implant procedures, and patient management.

Maximo DR 7278 Reference Manual

Introduction

References

Notice

The primary reference for background information is Zacouto FI, Guize LJ. Fundamentals of Orthorhythmic Pacing. In: Luderitz B, ed. Cardiac Pacing Diagnostic and Therapeutic Tools. New York: Springer-Verlag; 1976: 212-218.

See these additional references for more background information:

■

Singer I, Ed. Implantable Cardioverter-Defibrillator. Armonk, NY: Futura Publishing Co. 1994.

■

Singer I, Barold SS, Camm AJ, Eds. Nonpharmacological Therapy of Arrhythmias for the 21st Century: The State of the Art. Armonk, NY: Futura Publishing Co. 1998.

■

Estes M, Manolis AS, Wang P, Eds. Implantable Cardioverter-Defibrillators. New York, NY: Marcel Dekker, Inc.

1994.

■

Kroll MW, Lehmann MH, Eds. Implantable Cardioverter-Defibrillator Therapy: The Engineering-Clinical Interface. Norwell, MA: Kluwer Academic Publishers 1996.

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, INCIDENTIAL OR CONSEQUENTIAL DAMAGES TO ANY THIRD PARTY WHICH RESULTS FROM THE USE OF THE INFORMATION PROVIDED IN THE SOFTWARE.

Maximo DR 7278 Reference Manual

Abbreviations and acronyms

A- Atrial

AF Atrial Fibrillation

AFib/AFlutter Atrial Fibrillation and/or Atrial Flutter

ARP Atrial Refractory Period

ATP Antitachycardia Pacing

AVP Atrial Vulnerable Period

BOL Beginning of Life

bpm beats per minute

CNID Combined (VT and VF) Number of Intervals to Detect

CV Cardioversion

DF/Defib Defibrillation

ECG Electrocardiogram

Introduction

EGM Electrogram

EOL End of Life

ERI Elective Replacement Indicator

FDI Fibrillation Detection Interval

FTI Fast Ventricular Tachycardia Detection Interval

FVT Fast Ventricular Tachycardia

ICD Implantable Cardioverter Defibrillator

J joules

-1

reciprocal minutes; for example, pacing pulses per minute

min

ms milliseconds

mV millivolts

NCAP Non-Competitive Atrial Pacing

NID Number of Intervals to Detect

NST Non-Sustained Tachycardia

Maximo DR 7278 Reference Manual

Introduction

PAC Premature Atrial Contraction

PAV Paced A-V Delay

PES Programmed Electrical Stimulation

PMT Pacemaker-Mediated Tachycardia

P-P an atrial interval

ppm paces or pulses per minute

P-R an interval between a P-wave and the subsequent R-wave

PVAB Post Ventricular Atrial Blanking period

PVARP Post Ventricular Atrial Refractory Period

PVC Premature Ventricular Contraction

RAAV Rate Adaptive A-V delay

RNID Number of Intervals to Redetect

R-P an interval between an R-wave and the subsequent P-wave

R-R a ventricular interval

SAV Sensed A-V Delay

ST/Sinus Tach Sinus Tachycardia

SVT Supraventricular Tachycardia

TDI Tachycardia Detection Interval

V volts

V- Ve n tr ic ul ar

VF Ventricular Fibrillation

VF NID VF Number of Intervals to Detect

VRS Ventricular Rate Stabilization

VSP Ventricular Safety Pacing

VT Ventricular Tachycardia

VT NID VT Number of Intervals to Detect

Maximo DR 7278 Reference Manual

Quick overview

Part I

Maximo DR 7278 Reference Manual

Physical characteristics 18

Magnet application 19

Longevity projections 19

Replacement indicators 22

Typical charge times 23

High voltage therapy energy 23

Stored data and diagnostics 25

New and enhanced features 27

Quick reference1

Maximo DR 7278 Reference Manual

Chapter 1

Physical characteristics

Table 1-1. ICD physical characteristicsa

Volume 39 cc

Mass 76 g

H x W x D

Surface area of device can 67 cm

Radiopaque IDc

Materials in contact with human tissue

68 mm x 51 mm x 15 mm

PRM

Titanium / polyurethane / silicone rubber

Battery Lithium silver vanadium oxide

Connectors Two IS-1 connectors for pacing and

sensing, Two DF-1 connectors for high voltage therapy, Active Can electrode (programmable)

Device Port Connector

Typ e

Software Name

SVC DF-1 HVX

SVC

RV DF-1 HVB

Can n/a HVA, Can

V IS-1 bipolar

A IS-1 bipolar

Can

74lead.eps

Suture holes

78Suture.eps

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

Grommets may protrude slightly beyond the can surface.

Engineering series number follows the radiopaque code.

These materials have been successfully tested for the ability to avoid biological incompatibility. The device does not produce an injurious temperature in the surrounding tissue.

Maximo DR 7278 Reference Manual

Magnet application

Bringing a magnet close to the device triggers changes in device operation as shown in Table 1-2. When the magnet is removed, the device returns to its programmed operations.

Table 1-2. 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 seconds or less)

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

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

The Test tone does not sound if “VF Detection/Therapy Off” is the only alert enabled.

Quick reference

Magnet application

with programmable alert(s) enabled:

■

continuous tone (Test)

■

on/off intermittent tone (seek follow-up)

■

high/low dual tone (urgent follow-up)

with programmable alerts disabled:

■

no tone

■

high/low dual tone (urgent follow-up)

Longevity projections

Longevity estimates are based on accelerated battery discharge data and device modeling with EGM pre-storage off, 60 ppm

-1

(min

) pacing rate, with:

■

2.5 V pacing pulse amplitude, 0.4 ms pacing pulse width, and 35 J delivered therapy energy (see Table 1-3)

■

3 V pacing pulse amplitude, 0.4 ms pacing pulse width, and 35 J delivered therapy energy (see Table 1-4)

■

This model assumes default automatic capacitor formation setting. As a guideline, each full energy charge decreases device longevity by approximately 31 days.

Maximo DR 7278 Reference Manual

Chapter 1

Longevity projections

Table 1-3. Projected longevity in years with 2.5 V pacing amplitude and

0.4 ms pulse width

EGM pre-storage

500 ohm

pacing impedance

900 ohm pacing impedance

Percent pacing

Maximum energy charging frequency

DDD VVI DDD VVI

0% Semi-Annual Off 8.5 8.5 8.5 8.5

On 8.3 8.3 8.3 8.3

Quarterly Off 7.1 7.1 7.1 7.1

On 7.0 7.0 7.0 7.0

15% Semi-Annual Off 8.1 8.4 8.3 8.5

On 7.9 8.2 8.1 8.3

Quarterly Off 6.9 7.1 7.0 7.1

On 6.7 6.9 6.8 7.0

50% Semi-Annual Off 7.4 8.0 7.9 8.3

On 7.2 7.8 7.7 8.1

Quarterly Off 6.4 6.8 6.7 7.0

On 6.2 6.6 6.5 6.8

100% Semi-Annual Off 6.6 7.5 7.3 8.0

On 6.4 7.3 7.2 7.8

Quarterly Off 5.7 6.4 6.3 6.8

On 5.6 6.3 6.2 6.6

Maximum energy charging frequency may include full energy therapy shocks or capacitor formations.

The data provided for programming EGM pre-storage on is based on a 6 month period (two 3-month follow-up intervals) over the life of the device. Additional use of EGM pre-storage reduces longevity by approximately 27% or 3 months per year.

Maximo DR 7278 Reference Manual

Quick reference

Longevity projections

Table 1-4. Projected longevity in years with 3 V pacing amplitude and

0.4 ms pulse width

Percent pacing

0% Semi-Annual Off 8.5 8.5 8.5 8.5

15% Semi-Annual Off 8.0 8.3 8.2 8.4

50% Semi-Annual Off 7.1 7.8 7.6 8.1

100% Semi-Annual Off 6.1 7.2 6.9 7.8

Maximum energy charging frequency may include full energy therapy shocks or capacitor formations.

Maximum energy charging frequency

EGM pre-storage

500 ohm

pacing impedance

900 ohm pacing impedance

DDD VVI DDD VVI

On 8.3 8.3 8.3 8.3

Quarterly Off 7.1 7.1 7.1 7.1

On 7.0 7.0 7.0 7.0

On 7.8 8.1 8.0 8.2

Quarterly Off 6.8 7.0 6.9 7.1

On 6.6 6.9 6.8 6.9

On 6.9 7.6 7.4 7.9

Quarterly Off 6.1 6.7 6.5 6.9

On 6.0 6.5 6.4 6.7

On 5.9 7.0 6.8 7.6

Quarterly Off 5.4 6.2 6.0 6.6

On 5.2 6.0 5.9 6.5

Maximo DR 7278 Reference Manual

Chapter 1

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 programmer displays the date when the battery reached ERI on the Quick Look and Battery and Lead Measurements screens.

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 which 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.

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

Maximo DR 7278 Reference Manual

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).

Ta b l e 1 - 6 . Ty p ic a la full energy charge times

At Beginning of Life (BOL) 7.0 seconds

At Elective Replacement (ERI) 8.9 seconds

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

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.

Quick reference

Typical charge times

Maximo DR 7278 Reference Manual

Chapter 1

High voltage therapy energy

Table 1-7. Comparing delivereda (programmed) and storedb energy levels

Energy (J) Charge

Delivered a/

Stored

Programmed

35 39 7.0 10 12 2.0

32 37 6.4 9 10.5 1.8

30 34 6.0 8 9.3 1.6

28 32 5.6 7 8.2 1.4

26 30 5.2 6 7.1 1.2

25 29 5.0 5 5.9 1.0

24 27 4.8 4 4.8 0.8

22 25 4.4 3 3.6 0.6

20 23 4.0 2 2.4 0.4

18 21 3.6 1.8 2.2 0.4

16 19 3.2 1.6 2.0 0.3

15 17 3.0 1.4 1.7 0.3

14 16 2.8 1.2 1.5 0.2

13 15 2.6 1.0 1.2 0.2

12 14 2.4 0.8 1.0 0.2

11 13 2.2 0.6 0.8 0.1

Energy delivered at connector block into a 75 ohm 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.

Time

(sec)

Delivered a/ Programmed

Energy (J) Charge

Timec (sec)

Stored

0.4 0.5 0.1

Maximo DR 7278 Reference Manual

Stored data and diagnostics

Table 1-8. Stored data and diagnostics

Episode data

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

Quick reference

Stored data and diagnostics

EGM capacity for tachy episodes

14 minutes of dual-channel EGM, or 23.5 minutes of single-channel EGM

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

device does not usually store detailed episode records for NST episodes)

EGM capacity for SVT/NST episodes

2 minutes of dual-channel EGM, or 3.6 minutes of single-channel EGM

Brady episodes 53 mode switch episodes

EGM sources 9 options: atrial / ventricular / far-field

EGM options Store before onset; Store during charging

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

before latest VF, before latest VT, and before interrogation

Counter data

Detection counters Lifetime total, since cleared, and since last

session

Episode counters Episodes:

■

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

Maximo DR 7278 Reference Manual

Chapter 1

Stored data and diagnostics

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

Therapy efficacy counters

Other stored data

Counts for each VF, FVT, VT Therapy:

■

Delivered

■

Successful

■

Unsuccessful

■

Intervention (manually aborted)

Total number of aborted shocks

Patient Alert events Up to 10 log entries: text and date for the first

time an alert is triggered between interrogations

Battery and lead measurements

Battery voltage, last capacitor formation, last charge, lead impedance, EGM amplitude measurements, last high voltage therapy, and sensing integrity counter

Lead performance trends

14 days of daily measurements plus 80 weeks of weekly minimum and maximum measurements:

■

Lead impedance: atrial pacing, ventricular pacing, defibrillation pathway, and SVC lead (if used)

■

EGM amplitude: atrial (P-waves), ventricular (R-waves)

Cardiac Compass trends

14 months of measurement trends:

■

VT and VF episodes per day

■

High voltage therapies delivered per day

■

Ventricular rate during VT or VF

■

Episodes of non-sustained tachycardia per day

■

Heart rate variability

■

Total daily time in AF or AT

■

Ventricular rate during AF or AT

■

Percent pacing per day

■

Patient activity

■

Average day and night ventricular heart rate

Maximo DR 7278 Reference Manual

New and enhanced features

The following features are new or changed from the 7275 GEM III DR ICD.

Patient management

RapidRead telemetry – Communication between the device and

programmer is approximately 20 times faster than telemetry in previous Medtronic ICD devices. The magnitude of improvement depends on the amount and type of data that is interrogated. RapidRead telemetry is more reliable and has an increased range that makes placing the programming head easier.

Cardiac Compass trends report – This report displays up to 14 months of trend data related to tachyarrhythmia episodes, heart rate, and patient activity. See “Using Cardiac Compass to view long term clinical trends” on page 298.

Patient Alert – The alert duration when a magnet is applied to the device is now 20 seconds. The device also provides several new alerts:

■

SVC (HVX) lead impedance out of range

■

Active Can off without SVC

■

DOO/VOO mode programmed

■

VF Detection programmed off, or fewer than four VF therapies enabled for at least six hours

■

charge circuit timeout occurred

■

excessive charge time ERI

Quick reference

New and enhanced features

For more information, see “Using the Patient Alert feature” on page 259.

EGM amplitude trends – The device automatically measures R-wave and P-wave EGM amplitudes every day. These daily measurements are included in the data displayed on the Lead Performance Trends screen. See “Setting up data collection” on page 273.

Maximo DR 7278 Reference Manual

Chapter 1

New and enhanced features

EGM amplitude test – You can use the EGM Amplitude test to measure R-wave and P-wave EGM amplitudes. The results are reported on the EGM Amplitude Test screen. See “Measuring EGM Amplitude” on page 322.

Lead impedance measurement for SVC (HVX) – Along with other lead impedance measurements, the device provides an independent SVC (HVX) measurement to check the integrity of the supplementary high voltage electrode. See “Measuring lead impedance” on page 320.

Leadless ECG signal – If a supplementary high voltage electrode is placed in the SVC, the device provides the Leadless ECG signal through either the Can to SVC (HVX) or RV (HVB) to SVC (HVX) EGM source. See “Setting up data collection” on page 273.

Expanded pre-onset EGM storage – The device can now store up to 20 seconds of EGM before a tachycardia starts. See “Setting up data collection” on page 273.

Smart Auto Cap Formation – When the Auto Cap Formation Interval is set to Auto, the formation interval automatically adjusts to optimize device longevity and charge times. See “Smart Auto Cap” on page 216.

Ending a patient session – The device audits the programmed parameter settings when you end a patient session and alerts you if any of the settings are atypical. See “Starting and ending patient sessions” on page 234.

Tachyarrhythmia detection

VT Monitoring – VT detection can be set to Monitor, which allows

the device to detect and record VT episodes without delivering therapy or influencing VF detection. See “VT monitoring” on page 86.

High Rate Timeout – High Rate Timeout can turn off detection enhancements (Stability, PR Logic criteria) if a high rate episode is longer than a programmed duration. See “Details about High Rate Timeout” on page 113.

Maximo DR 7278 Reference Manual

Tachyarrhythmia therapy

Episode confirmation during and after charging – The device

continually monitors the ventricular rhythm during and after charging for cardioversion or defibrillation (when VF confirmation is active) to ensure the arrhythmia is present before delivering the high voltage shock. See “Confirming VF after initial detection” on page 126 and “Confirming VT or FVT after detection” on page 144.

Programmable Active Can – If a supplementary electrode is connected to the SVC (HVX) port, you can deselect the device Can as a high voltage electrode. See “Delivery pathway electrodes” on page 123.

Output – The device has a maximum delivered energy of 35 joules.

Bradycardia pacing

Quick reference

New and enhanced features

EP studies

Accelerometer-based rate response – The device uses an

accelerometer to provide rate responsive pacing.

Additional bradycardia pacing modes – The device provides asynchronous pacing in the DOO and VOO pacing modes and provides the ODO mode to disable pacing. See Chapter 8, “Treating bradycardia” on page 157.

Enhanced AT-style Mode Switch – Mode Switch episodes are detected using a combination of the median atrial rate and the AF evidence criterion. See “Details about Mode Switch” on page 192.

Defibrillation threshold testing support – The T-Shock and 50 Hz Burst induction screens allow you to monitor time between inductions, program ventricular sensing and VF therapy settings, adjust induction settings, select manual therapies, and retrieve episode records after therapy. See “How to perform defibrillation threshold testing” on page 57.

Maximo DR 7278 Reference Manual

Chapter 1

New and enhanced features

Backup VVI pacing during atrial inductions – You can choose to have the device deliver backup ventricular pacing during Manual Burst and PES inductions that are delivered to the atrium. See “EP Study overview” on page 328.

Maximo DR 7278 Reference Manual

System overview 32

Indications and usage 35

Contraindications 35

Patient screening 35

The Maximo DR system2

Maximo DR 7278 Reference Manual

Chapter 2

System overview

The Model 7278 Maximo DR Dual Chamber Implantable Cardioverter Defibrillator (ICD) system is an implantable medical device system that automatically detects and treats episodes of ventricular fibrillation, ventricular tachycardia, fast ventricular tachycardia, and bradyarrhythmia. The ICD system includes three major components:

■

ICD

The ICD senses the electrical activity of the patient’s heart via the sensing electrodes of the implanted atrial and ventricular leads. It then analyzes the heart rhythm based on selectable sensing and detection parameters. If the ICD detects a tachyarrhythmia, it delivers defibrillation, cardioversion, or antitachycardia pacing therapy to the patient’s heart. If the ICD identifies a bradyarrhythmia, it delivers bradycardia pacing therapy to the patient’s heart.

■

Leads

The ICD can be used with transvenous or epicardial defibrillation leads. The lead system should consist of bipolar or paired unipolar

pacing/sensing leads in each chamber of the heart and one or two high voltage cardioversion/ defibrillation electrodes. You can program the Active Can device case as a high voltage electrode. The pacing and sensing electrodes in each chamber sense cardiac activity and deliver pacing stimuli.

■

Programmer and software

The Medtronic programmer and 9978 application software allow you to perform the following tasks:

■

configure the detection, therapy, and bradycardia features for your patient

■

perform electrophysiological studies and system tests

■

monitor, display, or print patient cardiac activity information

■

view patient and device diagnostic data

With an appropriate unipolar to bipolar adapter kit.

Maximo DR 7278 Reference Manual

The Maximo DR devices and 9978 application software are compatible with the following programmer systems:

■

Medtronic CareLink Model 2090 programmer with a Model 2067 or 2067L programming head

■

Medtronic Model 9790C programmer with a Model 9767 or 9767L programming head

For information about:

■

indications, contraindications, lead compatibility, warnings and precautions, and patient selection, see the Maximo DR 7278 Implant Manual, which accompanies each device.

■

basic programmer and software desktop functions that are not included in Chapter 10, “Using the programmer” on page 221, see the manual accompanying the programmer.

■

installing the programming head, see the manual accompanying the programming head.

■

implanting leads, refer to the manuals accompanying the leads.

Detecting and treating tachyarrhythmias

The Maximo DR system

System overview

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

■

Upon detection of VF, the ICD delivers a biphasic defibrillation shock of up to 35 joules. If the VF episode persists, up to five more individually programmed defibrillation shocks can be delivered.

■

Upon detection of VT, the ICD delivers either a Ramp, Ramp+, or Burst antitachycardia pacing therapy or a biphasic cardioversion shock of up to 35 joules synchronized to a ventricular depolarization. If the VT episode persists, up to five more individually programmed VT therapies can be delivered. You can also program the ICD to monitor the VT episode without delivering therapy.

■

Upon detection of FVT, the ICD delivers either a Ramp, Ramp+, or Burst antitachycardia pacing therapy or a biphasic cardioversion shock of up to 35 joules synchronized to a ventricular depolarization. If the FVT episode persists, up to five more individually programmed FVT therapies can be delivered.

Maximo DR 7278 Reference Manual

Chapter 2

System overview

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

You can also program the ICD 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.

Treating bradycardia

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

Monitoring for real-time and stored data

The ICD and programmer provide real-time information on

detection and therapy parameters and status during a patient session. The ICD also provides accumulated data on device operation, including 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 arrhythmia episodes, therapies delivered, physical activity, heart rate, and bradycardia pacing activities.

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

Conducting electrophysiologic tests

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

Alerting the patient to system events

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.

Maximo DR 7278 Reference Manual

Indications and usage

The Model 7278 Maximo DR system is intended to provide ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life threatening ventricular arrhythmias.

Contraindications

The Maximo DR system is contraindicated for

■

patients whose tachyarrhythmias may have transient or reversible causes, such as acute myocardial infarction, digitalis intoxication, drowning, electrocution, electrolyte imbalance, hypoxia, or sepsis.

■

patients with incessant VT or VF

■

patients who have a unipolar pacemaker

■

patients whose primary disorder is bradyarrhythmias or atrial arrhythmias

The Maximo DR system

Indications and usage

Patient screening

Prior to 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 the implantation of the device.

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.

Maximo DR 7278 Reference Manual

Emergency therapy3

Delivering emergency therapies 38

How to deliver emergency 35 joule defibrillation 40

How to deliver emergency cardioversion 41

How to deliver emergency fixed burst pacing 42

How to deliver emergency VVI pacing 44

Maximo DR 7278 Reference Manual

Chapter 3

Delivering emergency therapies

The device provides the following emergency therapies:

■

defibrillation

■

cardioversion

■

fixed burst pacing

■

emergency VVI pacing

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

The programmer resets the emergency defibrillation energy to 35 joules 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].

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.

Aborting an emergency therapy

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

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

Maximo DR 7278 Reference Manual

Emergency therapy

Delivering emergency therapies

Mechanical Emergency buttons on the Model 9790C programmer

If you press the red mechanical [Emergency] button on the programmer display panel, the programmer displays the Emergency screen. The mechanical yellow-on-blue [Deliver] button activates the emergency therapy displayed on the programmer screen. This button functions only when the Emergency screen is displayed.

Mechanical Emergency VVI button on the 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.

Temporary parameter values

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.

Delivery of Emergency VVI Pacing changes the programmed bradycardia pacing values to the emergency values (see page 43).

Maximo DR 7278 Reference Manual

Chapter 3

Delivering emergency therapies

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 resets the emergency defibrillation energy to its maximum value each time you select [Emergency] or select the [Defibrillation] option from an Emergency screen.

Parameters

Energy – Amount of energy delivered to the

heart by the therapy.

* Medtronic nominal setting

10, 11, ... 16 18, 20, 22, 24, 25, 26, 28, 30, 32, 35*J

Pathwaya – Direction the electrical current flows through the heart.

If Active Can is Off, the HVA (Can) electrode is not used as part of the high-energy delivery pathway.

How to deliver emergency 35 joule defibrillation

AX>B (fixed)

1. Position the programming head over the device.

2. Select [Emergency].

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

4. Select [DELIVER]. If delivery is not confirmed,

verify that the programming head is properly positioned and select [Retry] or [Cancel].

Maximo DR 7278 Reference Manual

Delivering emergency therapies

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 “Synchronizing cardioversion after charging” on page 145.

Parameters

Energy – Amount of energy delivered to the

heart by the therapy.

Pathway

through the heart.

If Active Can is Off, the HVA (Can) electrode is not used as part of the high-energy delivery pathway.

– Direction the electrical current flows

How to deliver emergency cardioversion

Emergency therapy

* Medtronic nominal setting

0.4, 0.6, ...1.8, 2, 3, ... 16 18, 20, 22, 24, 25, 26, 28, 30, 32, 35*J

AX>B (fixed)

1. Position the programming head over the device.

2. Select [Emergency].

3. Select [Cardioversion].

4. Accept the cardioversion energy shown on the screen, or select Energy and select a new value from the window.

5. Select [DELIVER]. If delivery is not confirmed,

verify that the programming head is properly positioned and select [Retry] or [Cancel].

Maximo DR 7278 Reference Manual

Chapter 3

Delivering emergency therapies

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.

Parameters

How to deliver emergency fixed burst pacin

Interval – Time interval between pacing

pulses delivered during the fixed burst therapy.

V. Amplitude – Voltage of the ventricular pacing pulses delivered during the fixed burst therapy.

V. Pulse Width – Duration of the ventricular pacing pulses delivered during the fixed burst therapy.

How to deliver emergency fixed burst pacing

* Medtronic nominal setting

100, 110, ... 350* 360, 370, ... 600 ms

8V(fixed)

1.6 ms (fixed)

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 Interval for 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].

Maximo DR 7278 Reference Manual

Enabling emergency VVI pacing

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 programmer display panel and selecting VVI Pacing on the screen. To disable emergency VVI pacing, reprogram the bradycardia pacing parameters from the Parameters screen.

Emergency therapy

Delivering emergency therapies

Parameters

How to deliver emergency fixed burst pacin

Pacing Mode– NBG Codea for the pacing

VVI mode provided during emergency VVI pacing.

Lower Rate – Minimum pacing rate to

70 min

-1

maintain adequate heart rate during periods of inactivity.

V. Amplitude – Voltage of the ventricular

6V pacing pulses delivered during emergency VVI pacing.

V. Pulse Width – Duration of the

1.6 ms ventricular pacing pulses delivered during emergency VVI pacing.

V. Pace Blanking – Time interval during

240 ms which sensing is disabled after a pacing pulse.

Hysteresis – Enables tracking of intrinsic

Off heart rate below programmed Lower Rate to prevent pacing during extended periods of inactivity, such as when a patient is sleeping.

V. Rate Stabilization – Modifies the

Off pacing rate to eliminate the long pause that typically follows a premature ventricular contraction.

N–North American Society of Pacing and Electrophysiology (NASPE), B–British Pacing and Electrophysiology Group (BPEG), G–Generic Pacemaker Code

Maximo DR 7278 Reference Manual

Chapter 3

Delivering emergency therapies

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

-1

(70 min

■

V. Amplitude: 6 V

■

V. Width: 1.6 ms

■

V. Pace Blanking: 240 ms

■

Hysteresis: Off

■

V. Rate Stabilization: Off

)

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

Maximo DR 7278 Reference Manual

Part II

Device implant and patient follow-up procedures

Maximo DR 7278 Reference Manual

Implanting the ICD4

Overview 48

Preparing for an implant 48

Replacing an ICD 50

Positioning the leads 51

Testing sensing and pacing thresholds 53

Connecting the leads to the ICD 54

Testing defibrillation operation and effectiveness 55

Positioning and securing the ICD 58

Completing the implant procedure 59

Maximo DR 7278 Reference Manual

Chapter 4

Overview

Preparing for an implant

The tasks for implanting an ICD include

1. Preparing for an implant

2. Replacing an ICD

3. Positioning the leads

4. Testing sensing and pacing thresholds

5. Connecting the leads to the ICD

6. Testing defibrillation operation and effectiveness

7. Positioning and securing the ICD

8. Completing the implant procedure

These tasks are described in the sections that follow.

Warning: Keep a back-up external defibrillator available during the implant for transthoracic rescue when arrhythmias are induced.

Equipment for an implant

The equipment that is needed for an implant is as follows:

■

Medtronic CareLink Model 2090 programmer with a Model 2067 or 2067L programming head, or a Model 9790C programmer with a Model 9767 or 9767L programming head

■

Maximo Model 9978 software application

■

Model 2290 or 8090 Analyzer lead analysis device or equivalent pacing system analyzer

■

external defibrillator

Maximo DR 7278 Reference Manual

Sterile supplies for an implant

The sterile supplies that are needed for an implant are as follows:

■

implantable device and lead system components

■

programming head sleeve or programming head

■

analyzer cables

■

lead introducers appropriate for the lead system

■

extra stylets of appropriate length and shape

How to prepare for implanting

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 Maximo DR Model 9978 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.

Implanting the ICD

Preparing for an implant

Preprogram the device

Before opening the sterile package, prepare the ICD 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 could be reduced.

2. Interrogate the ICD, and print a full summary report.

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

If the device has been exposed to lower temperatures or has delivered a recent high voltage charge, the battery voltage will be temporarily lower.

4. Set up data collection parameters and the ICD internal clock (see page 275).

5. Perform a manual capacitor formation (see page 324).

6. Program the therapy and pacing parameters to values appropriate for the patient (see page 161). Ensure that all tachyarrhythmia detection is programmed Off (see page 72).

Use the Quick Look screen to verify the voltage, see page 257.

Maximo DR 7278 Reference Manual

Chapter 4

Replacing an ICD

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

When implanting the ICD 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.

■

Confirm adequate sensing during VF.

■

Ensure proper fit of the lead connectors in the ICD 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.

How to explant and replace an ICD

1. Program all tachyarrhythmia detection Off.

2. Dissect the leads and the ICD 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 ICD 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 ICD.

7. Evaluate the defibrillation efficacy of the replacement system.

Maximo DR 7278 Reference Manual

Positioning the leads

Implant endocardial leads according to the supplied instructions, unless suitable chronic leads are already in place. Do not use any lead with this device without first verifying connector compatibility (refer to the Maximo DR 7278 Implant Manual). Transvenous or epicardial leads may be used. A bipolar atrial lead with closely spaced pacing and sensing electrodes is recommended.

Using transvenous leads

Use standard transvenous implant techniques to position the ventricular lead tip in the right ventricular apex and the atrial pacing lead tip high on the right atrial appendage.

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

■

SVC (HVX) lead: Place the lead tip high in the innominate vein, approximately 5 cm proximal to the right atrium (RA) and SVC junction.

■

SQ patch: Place the patch along the left mid-axillary, centered over the fourth-to-fifth intercostal space.

■

CS lead: Advance the lead tip to just under the left atrial appendage, if possible.

Implanting the ICD

Positioning the leads

If using a subclavian approach, position the lead laterally to avoid pinching the lead body between the clavicle and the first rib.

Warning: Pinching the lead can damage the lead conductor or insulation, which may cause unwanted high voltage therapies or result in the loss of sensing or pacing therapy.

Maximo DR 7278 Reference Manual

Chapter 4

Positioning the leads

Using epicardial leads

A variety of surgical approaches can be used to implant epicardial leads, including a limited left thoracotomy or median sternotomy. A typical placement may use an anterior right ventricular patch as the RV (HVB) and a posterolateral left ventricular patch as SVC (HVX).

Follow the general guidelines below for positioning epicardial leads:

■

If unipolar epicardial pacing leads are used, position the electrodes about 1 to 2 cm apart to reduce electromagnetic interference, and route the leads together with several loose twists.

■

Suture the smooth face of each patch lead against the epicardium or pericardium in locations that produce optimal defibrillation.

■

Place the patches so that they encompass the maximum amount of cardiac mass and they have approximately equal amounts of mass between them.

■

Ensure that the patches do not overlap and the electrode portions do not touch.

■

Avoid placing extra-pericardial patches over the phrenic nerve.

Surgical incisions

A single-incision submuscular or subcutaneous approach is recommended when the ICD is implanted in the pectoral region. Make the implant pocket about 1.5 times the size of the ICD.

Submuscular implant – An incision extending over the deltoid-pectoral groove typically provides access to the cephalic and subclavian veins as well as the implant pocket. Place the ICD sufficiently medial to the humeral head to avoid interference with shoulder motion.

Subcutaneous implant – A transverse incision typically permits isolation of the cephalic vein. Place the ICD far medially to keep the leads away from the axilla. Make sure that the upper edge of the ICD remains inferior to the incision.

Maximo DR 7278 Reference Manual

Testing sensing and pacing thresholds

Sensing and pacing tests include the following measurements:

■

EGM amplitude

■

slew rate

■

pacing threshold

■

pacing lead impedance

Medtronic recommends that you use a Model 2290 or 8090 Analyzer lead analysis device to perform sensing and pacing measurements. If you use a Pacing System Analyzer (PSA), perform both atrial and ventricular measurements via the ventricular channel of the PSA.

Refer to the technical manual for the Analyzer you use to find details on performing sensing and pacing measurements.

Parameters

Measured sensing and pacing values must meet the following specific requirements at implant.

Implanting the ICD

Considerations

Table 4-1. Sensing and pacing values at implant

Measurement Acute Transvenous Leads Chronic Leads

R- wave amplitude ≥ 5 mV ≥ 3 mV

P- wave amplitude ≥ 2 mV ≥ 1 mV

Slew rate:

atrial ≥ 0.5 V/s ≥ 0.3 V/s

ventricular ≥ 0.75 V/s ≥ 0.5 V/s

Capture threshold

atrial ≤ 1.5 V ≤ 3.0 V

ventricular ≤ 1.0 V ≤ 3.0 V

At 0.5 ms pulse width

When measuring sensing and pacing values, measure between the tip (cathode) and ring or coil (anode) of each bipolar pacing/sensing lead.

Maximo DR 7278 Reference Manual

Chapter 4

Connecting the leads to the ICD

For unipolar epicardial pacing leads, either electrode can be the cathode; use the configuration that yields the lower pacing threshold.

Note: Do not measure the intracardiac EGM telemetered from the ICD to assess sensing.

Connecting the leads to the ICD

For more detailed information about lead/connector compatibility, see the Maximo DR 7278 Implant Manual, or contact Medtronic Technical Services at 1-800-723-4636.

Table 4-2. Lead connections

Can

SVC

Device Port

SVC DF-1 HVX

RV DF-1 HVB

Can n/a HVA, Can

V IS-1 bipolar

74lead.eps

A IS-1 bipolar

Connector Type

Software Name

Warning: Loose lead connections may result in inappropriate

sensing and failure to deliver necessary arrhythmia therapy.

Caution: Use only the torque wrench supplied with the device. It is designed to prevent damage to the device from overtightening a setscrew.

For easier lead insertion, insert the ventricular IS-1 leg before the other legs.

Maximo DR 7278 Reference Manual

Testing defibrillation operation and effectiveness

How to connect the lead to the device

74SetScrew.eps

74LeadTIp.eps

Implanting the ICD

1. Insert the torque wrench into the appropriate setscrew.

a. If the port is obstructed, 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 pull on the lead until all setscrews have been tightened.

5. Repeat these steps for each lead.

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 “Solving tachyarrhythmia therapy problems” on page 354.

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

20 - 200 ohms

≤ 25 J

Maximo DR 7278 Reference Manual

Chapter 4

Testing defibrillation operation and effectiveness

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

How to prepare for defibrillation threshold testing

1. Place the programming head over the ICD, 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 ICD is sensing properly.

3. Conduct a manual Lead Impedance Test lead connections. Perform this test with the ICD 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 ICD to properly detect VF with an adequate safety margin (1.2 mV sensitivity).

See “Measuring lead impedance” on page 320.

to verify the defibrillation

Maximo DR 7278 Reference Manual

Testing defibrillation operation and effectiveness

How to perform defibrillation threshold testing

Implanting the ICD

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].

Maximo DR 7278 Reference Manual

Chapter 4

Positioning and securing the ICD

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 energy level.

13. Wait until the on-screen timer reaches 5 minutes, then repeat steps 9 through 12 as desired.

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

Positioning and securing the ICD

Cautions: If no SVC electrode is implanted, the pin plug

provided with the device must be secured in the SVC port.

Program tachyarrhythmia detection Off before closing.

How to position and secure the device

Suture Hole Locations

Maximo DR 7278 Reference Manual

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. This position optimizes the ambulatory monitoring operations.

4. Suture the device securely within the pocket to

78Suture.eps

minimize post-implant rotation and migration of the device. Use a surgical needle to penetrate the suture holes.

Completing the implant procedure

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

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 one month post implant).

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

4. Program patient information. See “How to view and enter new patient information” on page 307.

5. Configure the Patient Alert feature. See “Using the Patient Alert feature” on page 259.

6. Set up data collection parameters. See “Setting up data collection” on page 273.

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

8. 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” on page 327.

9. Recheck pacing and sensing values, and adjust if necessary.

Implanting the ICD

Completing the implant procedure

Maximo DR 7278 Reference Manual

Conducting a patient follow-up

Patient follow-up guidelines 62

Verifying the status of the implanted system 62

Verifying accurate detection and appropriate therapy 63

Verifying effective bradycardia pacing 65

session

Maximo DR 7278 Reference Manual

Chapter 5

Patient follow-up guidelines

Schedule regular patient follow-up sessions to monitor the condition of the ICD and leads and to verify that the ICD 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 three 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

■

verify that the device is functioning correctly.

■

review the clinical performance and long term trends.

■

print appropriate reports1 to compare the results to the patient’s history and to retain for future reference.

Note: The Checklist feature provides a standard list of tasks to perform at a complete follow-up visit. You can also customize your own checklists if you wish. See “Streamlining follow-ups with Checklist” on page 267 for more information.

Verifying the status of the implanted system

To verify that the ICD and leads are functioning correctly, review the following information from the Quick Look screen and perform follow-up tests as indicated:

■

Review the displayed battery voltage for comparison to the Elective Replacement Indicator value (see page 22). 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 “Optimizing charge time” on page 214.

– If the programmer displays an Excessive Charge Time ERI,

the ICD should be replaced immediately.

See “Using Cardiac Compass to view long term clinical trends” on page 298 for information on this new report.

Maximo DR 7278 Reference Manual

Conducting a patient follow-up session

Verifying accurate detection and appropriate therapy

■

Review the defibrillation and pacing lead impedance values for inappropriate values or large changes since the last follow-up. See “Measuring lead impedance” on page 320.

■

Perform an EGM Amplitude test in each chamber for comparison to previous EGM Amplitude measurements. See “How to perform an EGM Amplitude test” on page 323.

■

To review longer term trends in sensing and impedance measurements, select the [>>] button from the lead impedance area of the Quick Look screen. The programmer displays a detailed history of automatic sensing and impedance measurements. See “Taking a quick look at device activity” on page 257.

Verifying accurate detection and appropriate therapy

To verify that the ICD 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 “Viewing episode data” on page 284.

■

Check stored SVT episode records for appropriate identification of SVTs.

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.

Maximo DR 7278 Reference Manual

Chapter 5

Verifying accurate detection and appropriate therapy

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 “Sensing integrity counter” on page 279.

If the ICD is oversensing, consider these programming options:

■

Increase the Pace Blanking value.

■

Increase the sensitivity threshold.

Caution: Do not re-program the ICD to decrease oversensing without assuring that appropriate sensing is maintained. See “Setting up sensing” on page 73.

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 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 “Detecting FVT episodes” on page 88.

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 “Enhancing detection with PR Logic criteria” on page 98, and “Enhancing VT detection with the Stability criterion” on page 108.

Maximo DR 7278 Reference Manual

Conducting a patient follow-up session

Verifying effective bradycardia pacing

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

■

Confirm that the patient is receiving adequate cardiac support for daily living activities.

■

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

■

Review the recorded Mode Switch episodes for comparison to the patient’s atrial arrhythmia history. A dramatic increase in frequency or duration of atrial episodes may indicate a need for investigation and analysis.

To display more detailed information about the Mode Switch episodes, perform these steps: select Episodes and Counters from the Data icon; select the Mode Switch episodes from the listed episode counters; then select the [Open Data] button.

■

Review the Cardiac Compass report for comparison to patient history (see page 298).

■

Conduct pacing threshold tests (see page 317) to verify that the programmed pacing outputs provide a sufficient safety margin.

Considerations

Review the following information before verifying bradycardia pacing.

Atrial Pacing – If the conduction history shows 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.

Maximo DR 7278 Reference Manual

Chapter 5

Verifying effective bradycardia pacing

Ventricular Pacing – If the ventricle is predominantly paced and the patient exhibits adequate ventricular response, consider these options:

■

Decrease the Lower Rate.

■

Increase the AV delays.

Conduction History – If the reported percentages in the conduction history do not add up to 100, the percentages may be rounded. Frequent premature contractions or A:V dissociation may also be the cause. Consider any of the following options:

■

Program the pacing mode to DDD or DDDR to promote A-V synchrony. (If appropriate, enable Mode Switch to keep the benefits of DDIR pacing during atrial high rate episodes.)

■

Enable Ventricular Rate Stabilization to smooth the heart rate following premature ventricular beats.

Maximo DR 7278 Reference Manual

Part III

Configuring the ICD for the patient

Maximo DR 7278 Reference Manual

Detecting tachyarrhythmias6

Detection overview 70

Setting up sensing 73

Detecting VF episodes 78

Detecting VT episodes 82

Detecting FVT episodes 88

Detecting tachyarrhythmia episodes with Combined Count 93

Monitoring episodes for termination or redetection 95

Enhancing detection with PR Logic criteria 98

Enhancing VT detection with the Stability criterion 108

Detecting double tachycardias 111

Detecting prolonged tachyarrhythmias with High Rate Timeout 112

Key terms 114

Maximo DR 7278 Reference Manual

Chapter 6

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.

Figure 6-1 shows how all of these detection features interact during initial detection. 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 “How to program VF detection” on page 80.

Maximo DR 7278 Reference Manual

Detecting tachyarrhythmias

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

Detection overview

Ye s

No / suspended by High Rate Timeout

Ye s

Update counts and pattern information

Has High Rate Timeout suspended detection

Does Stability reset the VT event count?

Are one or more PR Logic criteria on?

Is the median ventricular interval less than the SVT

Ventricular Event

Is the interval in the

VF, FVT, or VT detection zone?

Ye s

enhancements?

(VT and FVT via VT detection only)

Has a tachyarrhythmia event count

reached an NID?

Ye s

Limit?

Ye s

Tachy

Episode

Detected

Ye s

Is there a double tachycardia in progress?

Are one or more PR Logic criteria withholding

detection?

Maximo DR 7278 Reference Manual

Ye s

Chapter 6

Detection overview

Suspending tachyarrhythmia detection

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

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 page 93) 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 a High Rate Timeout Therapy operation, VT detection is not suspended (see page 114).

Maximo DR 7278 Reference Manual

Setting up sensing

The device provides bipolar sensing in both the atrium and ventricle via the sensing electrodes of the implanted atrial and ventricular 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 details about sensing on page 76.

Parameters

V. Sensitivity (mV) – Minimum amplitude of

electrical signal that registers as a sensed ventricular event.

Detecting tachyarrhythmias

Setting up sensing

* Medtronic nominal setting

0.15, 0.3*, 0.45, 0.6,

0.9, 1.2

Considerations

A. Sensitivity (mV) – Minimum amplitude of

electrical signal that registers as a sensed atrial event.

0.15, 0.3*, 0.45, 0.6,

0.9, 1.2, 1.5, 2.1

Review the following information before programming sensing parameters.

Dual chamber sensing and bradycardia pacing modes – The device senses in both the atrium and the ventricle at all times, except when the programmed bradycardia pacing mode is DOO or VOO. When the pacing mode is programmed to DOO or VOO mode, there is no sensing in the ventricle. In order to program either DOO or VOO 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.

Maximo DR 7278 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 ventr icular 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.

Maximo DR 7278 Reference Manual

Detecting tachyarrhythmias

Setting up sensing

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.

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.

How to program sensitivity

1. Select Params > Detection.

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

3. Select [PROGRAM].

Maximo DR 7278 Reference Manual

Chapter 6

Setting up sensing

Details about sensing

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. Figure 6-2 shows how sensitivity thresholds are adjusted after different types of events.

Figure 6-2. Auto-adjusting sensitivity thresholds

A S

Sensitivity Threshold

V P

74Autoadjust.eps

Rectified and

Filtered A. EGM

Rectified and

Filtered V. EGM

Marker Channel

1 2

A S

A P

V S

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.

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

Maximo DR 7278 Reference Manual

Detecting tachyarrhythmias

Setting up sensing

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 (sense blanking in the opposite chamber) after a sensed event.

■

Atrial sensing is still active during the Post-Ventricular Atrial Blanking (PVAB) period (see “Post-Ventricular Atrial Blanking Period” on page 170).

Table 6-1 shows the duration of the fixed blanking periods. For information on programmable pace blanking periods, see page 158.

Table 6-1. Fixed blanking periods

Cross-chamber blanking after atrial or ventricular pacing pulse 30 ms

Atrial blanking after sensed atrial event 100 ms

Ventricular blanking after sensed ventricular event 120 ms

Atrial and ventricular blanking after delivered cardioversion or defibrillation therapy

Maximo DR 7278 Reference Manual

520 ms

Chapter 6

Detecting VF episodes

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.

Synchronization refractory periods help prevent the device from delivering cardioversion and defibrillation therapies at inappropriate times. See “Synchronizing defibrillation without confirming VF” on page 125 and “Synchronizing cardioversion after charging” on page 145.

Note: Refractory periods do not affect tachyarrhythmia detection.

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 details about VF detection on page 80.

Parameters

VF Detection Enable – Turns VF

detection on or off.

VF Interval (ms) – 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.

Maximo DR 7278 Reference Manual

* Medtronic nominal setting

On*, Off

240, 250, . . ., 320*, . . .,400

12/16, 18/24*, 24/32, 30/40, 45/60, 60/80, 75/100, 90/120, 105/140, 120/160

6/8, 9/12, 12/16*, 18/24, 21/28, 24/32, 27/36, 30/40

Considerations

Detecting tachyarrhythmias

Detecting VF episodes

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 less than 300 ms.

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

■

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 “Enhancing detection with PR Logic criteria” on page 98.

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 “Detecting double tachycardias” on page 111.

Maximo DR 7278 Reference Manual

Chapter 6

Detecting VF episodes

Restrictions

How to program VF detection

Review the following information before programming VF Detection parameters.

Tachyarrhythmia detection and bradycardia pacing – To e n s u r e reliable ventricular tachyarrhythmia detection, the programmer regulates the values available for bradycardia pacing and tachyarrhythmia detection. See “Parameter interlocks” on page 392.

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.

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].

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 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).

Maximo DR 7278 Reference Manual

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 VF and delivers the next programmed VF therapy.

Note: The device can also detect VF Episodes via the Combined Count detection criterion (see page 93).

Figure 6-3. Device detects VF

ECG

Detecting tachyarrhythmias

Detecting VF episodes

1 2 3

A S

A R

Marker Channel

FSFSFSFSFSFSFSFSFSF

VSVSV

VF Event Count

V S

VSV

FSFSF

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

FSFSF

VF Interval

200 ms

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.

74VFDetection.eps

Maximo DR 7278 Reference Manual

Chapter 6

Detecting VT episodes

Parameters

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 details about VT detection on page 84.

* Medtronic nominal setting

VT Detection Enable – Turns VT detection on or off, or enables VT monitoring.

On, Off*, or Monitor

VT Interval (Rate) (ms) – 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.

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.

Maximo DR 7278 Reference Manual

280, 290, . . ., 400*, . . ., 600

12, 16*, . . ., 52, 76, 100

4, 8, 12*, . . ., 52

Detecting tachyarrhythmias

Detecting VT episodes

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

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 “Detecting tachyarrhythmia episodes with Combined Count” on page 93.

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 “Enhancing VT detection with the Stability criterion” on page 108, and “Enhancing detection with PR Logic criteria” on page 98.

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 page 111).

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.

Maximo DR 7278 Reference Manual

Chapter 6

Detecting VT episodes

How to program VT detection

Details about VT detection

To program VT detection:

1. Select Params > Detection.

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

3. Select [PROGRAM].

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).

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 via the Combined Count detection criterion (see page 93).

Maximo DR 7278 Reference Manual

Figure 6-4. Device detects VT

ECG

132

Detecting tachyarrhythmias

Detecting VT episodes

A S

ARARARARARARA

Marker Channel

VT Event Count

V S

VSV

T S

10123456

TSTSTSTSTST

VT Interval

ECG

ARARARARARARARARARARARA

Marker Channel

T D

V S

74VTDetection.eps

VT Event Count

TSTSTSTSTSTSTSTST

78910111213141516

VT Interval

200 ms

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.

Maximo DR 7278 Reference Manual

Chapter 6

Detecting VT episodes

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.

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.

Maximo DR 7278 Reference Manual

Figure 6-5. Device detects and monitors VT

ECG

Detecting tachyarrhythmias

Detecting VT episodes

2 31

A S

ARARA

ARARARARA

A R

Marker Channel

VT Event Count

V S

VSTSTSTST

1234

TSTSTSTDTSTST

13 14 15 16 0 0 0

74VTmonitor.eps

VT Interval

200 ms

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.

Maximo DR 7278 Reference Manual

Chapter 6

Detecting FVT episodes

Parameters

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 details about FVT detection on page 90.

* Medtronic nominal setting

FVT Detection Enable – Enables FVT detection via the VF or the VT detection algorithm.

Off*, via VF, or via VT

Considerations

FVT Interval (Rate) (ms) – V-V

intervals between this value and the programmed VF Interval are marked as FVT events.

200, 210, . . ., 600

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.

Maximo DR 7278 Reference Manual

Detecting tachyarrhythmias

Detecting FVT episodes

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:

■

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 two 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 one 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.

Restrictions

Double tachycardia detection – When any PR Logic detection

criteria is enabled, the device also enables double tachycardia detection (VF, VT, or FVT in the presence of an SVT, see page 111).

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 “Parameter interlocks” on page 392.

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.

Maximo DR 7278 Reference Manual

Chapter 6

Detecting FVT episodes

How to program FVT detection

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.

To program FVT detection:

1. Select Params > Detection.

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

3. Select [PROGRAM].

Details about FVT detection

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

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 eight intervals:

■

If any of the last eight intervals are in the VF zone, it detects the episode as VF.

■

If all of the last eight intervals are outside the VF zone, it detects the episode as FVT (see Figure 6-6).

Maximo DR 7278 Reference Manual

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 eight intervals:

■

If any of the last eight intervals are in the VF or FVT zones, it detects the episode as FVT.

■

If all of the last eight 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 Count detection criterion (see page 93).

Figure 6-6. Device detects FVT via VF

Detecting tachyarrhythmias

Detecting FVT episodes

1 2

ECG

A S

ARARA

A R

ARARARARARARARARA

Marker Channel

VF Event Count

V S

1 1 2345

TFTFTFT

TFT

TFTFTFTFTFV

13 14 15 16 17 18

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.

74FvtDetect.eps

200 ms

Maximo DR 7278 Reference Manual

Chapter 6

Detecting FVT episodes

Figure 6-7. FVT zone merging

Zone merging after detection

To ensure 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.

FVT set to “via VF” FVT set to “via VT”

Before detection:

After VF detection:

After FVT detection:

FVT

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

FVT

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

FVT

All zones remain unchanged. VT and FVT zones merge, leaving a

larger FVT zone.

FVT

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

FVT

FVT1.eps

FVT2.eps

FVT3.eps

Maximo DR 7278 Reference Manual

Detecting tachyarrhythmias

Detecting tachyarrhythmia episodes with Combined Count

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.

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 six, 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 7 21/28 24

9/12 10 24/32 28

12/16 14 27/36 31

18/24 21 30/40 35

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Chapter 6

Detecting tachyarrhythmia episodes with Combined Count

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 eight intervals and classifies the episode as

■

VF, if any of the last eight were in the VF zone.

■

FVT, if FVT Detection is enabled and none of the last eight was in the VF zone, but one or more was in the FVT zone.

■

VT, if all eight were outside the VF zone (and FVT zone, if FVT detection is enabled).

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

ECG

ARARARARARARARARARARARA

ARARARARARARA

Marker Channel

VSF

VF Event Count

VT Event Count

Combined Count

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

FSFSFSFSF

FST

SFSFSFSFSFSFSFSFS

TST

FDV

VF and VT Interval

200 ms

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.

74Combined.eps

Maximo DR 7278 Reference Manual

Detecting tachyarrhythmias

Monitoring episodes for termination or redetection

Once the device detects an arrhythmia, it considers the episode 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 details about episode termination and redetection on

page 96.

Parameters

* Medtronic nominal setting

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

6/8, 9/12, 12/16*, 18/24, 21/28, 24/32, 27/36, 30/40

Considerations

VT Redetect NID – Number of

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

4, 8, 12*, . . . 52

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.

Maximo DR 7278 Reference Manual

Chapter 6

Monitoring episodes for termination or redetection

How to program redetection parameters

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.

1. Select Params > Detection.

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

3. Select [PROGRAM].

Episode termination

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

■

eight consecutive ventricular intervals are greater than or equal to the programmed VT interval.

■

20 seconds 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.

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

Maximo DR 7278 Reference Manual

Monitoring episodes for termination or redetection

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 “Detecting tachyarrhythmia episodes with Combined Count” on page 93).

The device then delivers the next programmed therapy for the current arrhythmia and resumes monitoring for the outcome of that therapy. Figure 6-9 shows an example of redetection.

Figure 6-9. VT episode redetected after therapy

ECG

Detecting tachyarrhythmias

2 31

ARASASASASASARARARARARARARARARARARARA

Marker Channel

VT Event Count

VT Interval

TPT P

TPT

TPTPTPTPTPTSTSTSTSTSTSTSTSTSTSTST

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

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.

Suspending VT 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 throughout an episode.

If the defibrillation therapy is delivered as a result of a High Rate Timeout Therapy operation, VT detection is not suspended (see page 114).

74Redetect.eps

200 ms

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Chapter 6

Enhancing detection with PR Logic criteria

VT acceleration

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

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.

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

■

“Details about PR Logic pattern and rate analysis” on page 102

■

“Details about the PR Logic detection criteria” on page 106

Parameters

Maximo DR 7278 Reference Manual

AFib/AFlutter – Identifies rapidly conducted

atrial fibrillation, atrial flutter, or atrial tachycardia.

Sinus Tach – Identifies sinus tachycardia. On

1:1 VT-ST Boundary (%) – Threshold between

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

* Medtronic nominal setting

Ona, Off*

, Off*

35, 50*, 66, 75, 85

Detecting tachyarrhythmias

Enhancing detection with PR Logic criteria

* Medtronic nominal setting

Considerations

Other 1:1 SVTs – Identifies other one-to-one

SVTs where the atrial and ventricular activation are roughly simultaneous.

SVT Limit (ms) – 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.

On, Off*

240, 250, . . ., 320*, 330, 340, . . ., 600

Review the following information before programming PR Logic parameters.

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 “Pattern analysis of A-V and V-A intervals” on page 102.

■

Use caution when programming the 1:1 VT-ST Boundary. Incorrect programming of this parameter can result in inappropriate therapies or underdetection of tachyarrhythmias.

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 page 111).

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 “Customizing PR Logic for patients with slow conduction” on page 100.

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Chapter 6

Enhancing detection with PR Logic criteria

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.

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 “Pattern analysis of A-V and V-A intervals” on page 102.

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 on page 103.

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%.

Maximo DR 7278 Reference Manual

Medtronic 7278 Reference Guide

Specifications and Main Features

Frequently Asked Questions

User Manual

Table of contents

Introduction

Abbreviations and acronyms

Quick overview

Quick reference1

Physical characteristics

Magnet application

Longevity projections

Replacement indicators

Typical charge times

High voltage therapy energy

Stored data and diagnostics

New and enhanced features

The Maximo DR system2

System overview

Indications and usage

Contraindications

Patient screening

Emergency therapy3

Delivering emergency therapies

Device implant and patient follow-up procedures

Implanting the ICD4

Overview

Preparing for an implant

Replacing an ICD

Positioning the leads

Testing sensing and pacing thresholds

Connecting the leads to the ICD

Testing defibrillation operation and effectiveness

Positioning and securing the ICD

Completing the implant procedure

Patient follow-up guidelines

Verifying the status of the implanted system

Verifying accurate detection and appropriate therapy

Verifying effective bradycardia pacing

Configuring the ICD for the patient

Detecting tachyarrhythmias6

Detection overview

Setting up sensing

Detecting VF episodes

Detecting VT episodes

Detecting FVT episodes

Detecting tachyarrhythmia episodes with Combined Count

Monitoring episodes for termination or redetection

Enhancing detection with PR Logic criteria