Medtronic 7232CX Reference Guide

MAXIMO™ VR 7232Cx, 7232B, 7232E

Single Chamber Implantable Cardioverter Defibrillator (VVE-VVIR)

Reference Manual

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

MAXIMOTM VR 7232Cx, 7232B, 7232E

Reference Manual 0

A guide to the operation and programming of the Model 7232Cx, 7232B, and 7232E MaximoTM VR Single Chamber Implantable Cardoverter Defibrillator

The following are trademarks of Medtronic: Active Can, Cardiac Compass, Checklist, Decision Channel, Flashback, GEM,

Leadless ECG, Marker Channel, Maximo, Patient Alert, Quick Look, QuickLink, RapidRead, T-Shock, Wavelet

Introduction 11

Abbreviations and acronyms 13

Part I Quick overview

1 Quick reference 17

Physical characteristics 18

Magnet application 22

Longevity projections 23

Replacement indicators 26

Typical charge times 27

High-voltage therapy energy 27

Stored data and diagnostics 29

New and enhanced features 31

2 The Maximo VR system 37

System overview 38

Indications and usage 41

Contraindications 41

Patient screening 41

Table of contents

3 Emergency therapy 43

Delivering emergency therapies 44

Part II Device implant and patient follow-up procedures

4 Implanting the ICD 53

Overview 54

Preparing for an implant 54

Replacing an ICD 57

Positioning the leads 58

Testing sensing and pacing thresholds 60

Connecting the leads to the ICD 61

Testing defibrillation operation and effectiveness 65

Positioning and securing the ICD 67

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Table of contents

Completing the implant procedure 68

5 Conducting a patient follow-up session 69

Patient follow-up guidelines 70

Verifying the status of the implanted system 70

Verifying accurate detection and appropriate therapy 71

Verifying effective bradycardia pacing 73

Part III Configuring the ICD for the patient

6 Detecting tachyarrhythmias 77

Detection overview 78

Setting up sensing 81

Detecting VF episodes 85

Detecting VT episodes 90

Detecting FVT episodes 96

Detecting tachyarrhythmia episodes with Combined Count 101

Monitoring episodes for termination or redetection 104

Enhancing detection with Wavelet 107

Enhancing VT detection with the Onset criterion 116

Enhancing VT detection with the Stability criterion 121

Detecting prolonged tachyarrhythmias with High Rate Timeout 124

Key terms 126

7 Treating tachyarrhythmia episodes 131

Treating VF with defibrillation 132

Treating VT and FVT with antitachycardia pacing 143

Treating VT and FVT with cardioversion 153

Optimizing therapy with Smart Mode and Progressive Episode Therapies 161

Key terms 166

8 Treating bradycardia 169

Providing basic pacing therapy 170

Enhancing pacing for optimal cardiac output 174

Providing pacing after high-voltage therapies 185

Key terms 186

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Table of contents

9 Optimizing charge time and device longevity 189

Optimizing charge time 190

Optimizing device longevity 193

Key terms 194

Part IV Evaluating and managing patient treatment

10 Using the programmer 197

Setting up and using the programmer 198

Display screen features 199

Viewing and programming device parameters 206

Starting and ending patient sessions 210

Viewing live waveform traces 212

Recording live waveform strips 219

Saving and retrieving device data 221

Printing reports 225

Key terms 230

11 Using system evaluation tools 231

A summary of system evaluation tools 232

Taking a quick look at device activity 233

Using the Patient Alert feature 235

Streamlining follow-ups with Checklist 243

Key terms 246

12 Setting up and viewing collected data 247

A summary of data collection 248

Setting up data collection 249

Collecting lead performance data 255

Viewing the episode and therapy efficacy counters 257

Viewing episode data 260

Viewing Flashback Memory 268

Viewing battery and lead status data 270

Viewing lead performance trends 272

Using Cardiac Compass to view long term clinical trends 274

Viewing and entering patient information 279

Automatic device status monitoring 283

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Table of contents

Key terms 285

13 Testing the system 289

Testing overview 290

Evaluating the underlying rhythm 291

Measuring pacing thresholds 292

Testing the Wavelet criterion 295

Measuring lead impedance 299

Measuring EGM Amplitude 301

Testing the device capacitors 303

Key terms 305

14 Conducting electrophysiologic studies 307

EP Study overview 308

Inducing VF with T-Shock 310

Inducing VF with 50 Hz Burst 313

Inducing an arrhythmia with Manual Burst 316

Inducing an arrhythmia with PES 318

Delivering a manual therapy 320

Key terms 323

15 Solving system problems 325

Overview 326

Solving sensing problems 327

Solving tachyarrhythmia detection problems 328

Solving tachyarrhythmia therapy problems 330

Solving bradycardia pacing problems 331

Responding to device status indicators 332

Key terms 333

Appendices A Warnings and precautions 337

General warnings 338

Storage and handling 338

Resterilization 339

Device operation 340

Lead evaluation and lead connection 341

Follow-up testing 342

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Explant and disposal 343

Medical therapy hazards 343

Home and occupational environments 345

BDevice parameters347

Emergency settings 348

Detection parameters 349

Therapy parameters 351

Bradycardia pacing parameters 353

System maintenance parameters 354

Data collection parameters 356

System test and EP study parameters 357

Fixed parameters 360

Patient information parameters 361

Programmer symbols 362

Parameter interlocks 364

Index 365

Table of contents

Maximo VR 7232Cx, 7232B, 7232E 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 VR 7232Cx, 7232B, 7232E Reference manual

Chapter

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 VR 7232Cx, 7232B, 7232E Reference manual

Abbreviations and acronyms

ATP Antitachycardia Pacing

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

EGM Electrogram

EOL End of Life

ERI Elective Replacement Indicator

FDI Fibrillation Detection Interval

FTI Fast Ventricular Tachycardia Detection Interval

Abbreviations and acronyms

FVT Fast Ventricular Tachycardia

ICD Implantable Cardioverter Defibrillator

J joules

-1

reciprocal minutes; for example, pacing pulses per minute

min

ms milliseconds

mV millivolts

NID Number of Intervals to Detect

NST Non-sustained Tachycardia

PES Programmed Electrical Stimulation

ppm paces or pulses per minute

PVC Premature Ventricular Contraction

RNID Number of Intervals to Redetect

R-R a ventricular interval

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter

Abbreviations and acronyms

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

VT Ventricular Tachycardia

VT NID VT Number of Intervals to Detect

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Quick overview

Part I

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Physical characteristics 18

Magnet application 22

Longevity projections 23

Replacement indicators 26

Typical charge times 27

High-voltage therapy energy 27

Stored data and diagnostics 29

New and enhanced features 31

Quick reference1

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

Physical characteristics

Tab le 1- 1. ICD physical characteristicsa

Connector type Cx B or E

Volume 39 cc 45 cc

Mass 76 g 81 g

H x W x D

Surface area of

68 mm x 51 mm x 15 mm

67 cm

74 mm x 51 mm x 15 mm

64 cm

device can

Radiopaque IDc

PRN B-type connector PVF

E-type connector PVG

Materials in contact with human tissue

Titanium / polyurethane /

silicone rubber

Battery Lithium silver vanadium

oxide

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.

Titanium / polyurethane / silicone rubber

Lithium silver vanadium oxide

Tab le 1- 2. Cx-type connector characteristics

General description Device

One IS-1 connector for pacing and sensing, Two DF-1 connectors for high-voltage therapy, Active Can electrode (programmable).

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Port

Connector Typ e

Software Name

SVC DF-1 HVX

RV DF-1 HVB

Can — HVA, Can

V IS-1 bipolar

Figure 1-1. Cx-type connector

Quick reference

Physical characteristics

1 Suture holes

2 SVC port (DF-1)

3RV port (DF-1)

4 programmable Active Can

5V port (IS-1)

Tabl e 1-3 . B-type connector characteristics

General description Device

Port

Three 6.5 mm unipolar high-voltage ports and one

3.2 mm low profile bipolar pace/sense (IS-1 compatible) port.

HVB 6.5 mm HVB

HVA

HVX

Connector Typ e

6.5 mm HVX

Software Name

Can — HVA, Can

P/S bipolar pace

3.2 mm bipolar (IS-1 compatible)

sense

The HVA and HVX ports are electrically connected and are treated as the HVX electrode. For more information see “B- and E-type connector pathways” on page 136.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

Physical characteristics

Figure 1-2. B-type connector

1 Suture holes

2 HVB port (6.5 mm)

3 HVA port (6.5 mm)

4 programmable Active Can

5 HVX port (6.5 mm)

6 P/S port (3.2 mm)

Tab le 1- 4. E-type connector characteristics

General description Device

Port

Connector Typ e

Software Name

P+/S 5.0 mm

Two 6.5 mm unipolar high-voltage ports and two 5 mm unipolar pace/sense ports.

HVA 6.5 mm HVX

HVB 6.5 mm HVB

Can — HVA, Can

P-/S 5.0 mm

The HVA port of the E-type connector can be used as the HVX electrode when Active Can is programmed off. For more information, see “B- and E-type connector pathways” on page 136.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Figure 1-3. E-type connector

Quick reference

Physical characteristics

1 Suture holes

2 P+/S port (5.0 mm)

3 HVA port (6.5 mm)

4 programmable Active Can

5 HVB port (6.5 mm)

6 P-/S port (5.0 mm)

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

Magnet application

Bringing a magnet close to the device triggers changes in device operation as shown in Table 1-5. When the magnet is removed, the device returns to its programmed operations.

Tab le 1- 5. 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)

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)

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.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

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 1-6)

■

3 V pacing pulse amplitude, 0.4 ms pacing pulse width, and 35 J delivered therapy energy (see Table 1-7)

This model assumes default automatic capacitor formation setting. As a guideline, each full energy charge decreases device longevity by approximately 43 days.

Device longevity is affected by how certain features are programmed, such as EGM pre-storage. For more information, see “Optimizing device longevity” on page 193.

Considerations for using EGM pre-storage

When the EGM pre-storage feature is programmed off, the device starts to store EGM following the third tachyarrhythmia event and also provides up to 20 seconds of information before the onset of the tachyarrhythmia, including:

■

VV intervals

■

Marker Channel

■

interval plot Flashback

Quick reference

Longevity projections

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

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

■

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

■

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

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

Longevity projections

Tab le 1- 6. Projected longevity in years with 2.5 V pacing amplitude and

0.4 ms pulse width

Percent pacing

Maximum energy charging frequency

EGM pre-storage

500 ohm

impedance

pacing

900 ohm

pacing

impedance

0% Semi-Annual Off 10.1 10.1

On 9.8 9.8

Quarterly Off 8.3 8.3

On 8.1 8.1

15% Semi-Annual Off 9.8 10.0

On 9.6 9.7

Quarterly Off 8.1 8.2

On 7.9 8.0

50% Semi-Annual Off 9.3 9.7

On 9.1 9.5

Quarterly Off 7.8 8.0

On 7.6 7.8

100% Semi-Annual Off 8.7 9.3

On 8.5 9.1

Quarterly Off 7.3 7.7

On 7.1 7.6

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 VR 7232Cx, 7232B, 7232E Reference manual

Quick reference

Longevity projections

Tabl e 1-7 . Projected longevity in years with 3 V pacing amplitude and

0.4 ms pulse width

Percent pacing

0% Semi-Annual Off 10.1 10.1

15% Semi-Annual Off 9.8 9.9

50% Semi-Annual Off 9.1 9.5

100% Semi-Annual Off 8.2 9.0

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

Maximum energy charging frequency

EGM pre-storage

500 ohm

impedance

pacing

900 ohm

pacing

impedance

On 9.8 9.8

Quarterly Off 8.3 8.3

On 8.1 8.1

On 9.5 9.7

Quarterly Off 8.0 8.1

On 7.9 8.0

On 8.8 9.3

Quarterly Off 7.6 7.9

On 7.4 7.7

On 8.0 8.8

Quarterly Off 7.0 7.5

On 6.8 7.3

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

Replacement indicators

Battery voltage and messages about replacement status appear on the programmer display and on printed reports. Table 1-8 lists the Elective Replacement Indicator (ERI) and the End of Life (EOL) conditions.

Tab le 1- 8. 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% VVI pacing at 60 ppm (min

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 VR 7232Cx, 7232B, 7232E Reference manual

-1

), 3 V,

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 1-9).

Tabl e 1-9 . Ty p ic ala full energy charge times

At Beginning of Life (BOL) 7.0 seconds

At Elective Replacement (ERI) 9.1 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 1-10 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 VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

High-voltage therapy energy

Table 1-10. 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

0.4 0.5 0.1

Energy (J) Charge

Timec (sec)

Stored

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Stored data and diagnostics

Tabl e 1-1 1. Stored data and diagnostics

Episode data

Quick reference

Stored data and diagnostics

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

QRS Snapshot

EGM capacity for tachy episodes

14 minutesb of dual-channel EGM, or

23.5 minutes

of single-channel EGM

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

QRS Snapshota (the device does not usually store detailed episode records for NST episodes)

EGM capacity for SVT/NST episodes

2 minutes

3.6 minutese of single-channel EGM

of dual-channel EGM, or

EGM sources Six options: ventricular / far-field

EGM options Store before onset; Store during charging

Flashback memory 2000 intervals (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

■

NST episodes and SVTs

Percentage pacing:

■

VS and VP percentages

Additional counters:

■

Single PVCs and PVC runs

■

Rate stabilization pulses and runs

Therapy efficacy counters

Counts for each VF, FVT, VT Therapy:

■

Delivered

■

Successful

■

Unsuccessful

■

Intervention (manually aborted)

Total number of aborted shocks

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

Stored data and diagnostics

Tab le 1- 11. Stored data and diagnostics (continued)

Other stored data

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

■

Ventricular EGM amplitude (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

■

Percent of time pacing is active

■

Patient activity

■

Average day and night ventricular heart rate

When Wavelet is set to On or Monitor

13.5 minutes if Wavelet is set to On or Monitor

22 minutes if Wavelet is set to On or Monitor

1.6 minutes if Wavelet is set to On or Monitor.

2.75 minutes if Wavelet is set to On or Monitor.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

New and enhanced features

The following features are new or changed from the 7231 GEM III VR ICD.

Lead connection header options

The Maximo VR supports three types of lead connection headers. The connection types are Cx, B, and E.

■

Cx-type connector is normally used with one multipolar transvenous lead in the ventricle for sensing, pacing, and delivering therapies.

■

B-type connector is normally used with one multipolar transvenous lead in the ventricle for sensing and pacing and with two or three high-voltage electrodes placed to deliver cardioversion/defibrillation therapies.

■

E-type connector is normally used with two 5 mm unipolar myocardial pacing and sensing lead connectors and two

6.5 mm high-voltage lead connectors.

Quick reference

New and enhanced features

Regardless of the connector type used, the Active Can feature may be programmed so that the device Can serves as a second high-voltage electrode and the HVX port third high-voltage electrode if desired. For more information about connection pathways, see “B- and E-type connector pathways” on page 136.

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 274.

can accommodate a

The HVA port of the B- or E-type connector serves as the HVX electrode.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

New and enhanced features

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

■

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

For more information, see “Using the Patient Alert feature” on page 235.

EGM amplitude trends – The device automatically measures R-wave EGM amplitudes every day. These daily measurements are included in the data displayed on the Lead Performance Trends screen. See “Collecting lead performance data” on page 255.

EGM Amplitude test – You can use the EGM Amplitude test to measure R-wave EGM amplitudes. The results are reported on the EGM Amplitude test screen. See “Measuring EGM Amplitude” on page 301.

Lead impedance measurements for SVC (HVX)

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 299.

Leadless ECG signal – If a supplementary high-voltage electrode is placed in the SVC 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 249.

SVC refers to the HVX electrode. For pathway information, see “B- and E-type connector pathways” on page 136.

The HVA port of the B- or E-type connectors serves as the HVX electrode.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

– Along with

, the device provides the

Quick reference

New and enhanced features

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 249.

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 192.

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 210.

Wavelet test – The Wavelet test allows you to manually collect and assess the template used by the Wavelet criterion. See “Testing the Wavelet criterion” on page 295.

Auto Collection for Wavelet – The Wavelet criterion includes the option to have the device automatically collect and maintain the template used to distinguish between SVT and ventricular tachyarrhythmia. See “Details about Auto Collection” on page 114.

QRS Snapshot data – When the Wavelet criterion is programmed to On or Monitor, the device stores QRS Snapshot data with VT, VF, FVT and SVT episode records. This data includes graphical representations of up to eight QRS complexes, along with match scores and event classifications as “Match” or “No Match.”

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 1

New and enhanced features

Tachyarrhythmia detection

Wavelet Dynamic Discrimination criterion – The Wavelet

criterion is designed to prevent detection of rapidly conducted SVTs as ventricular tachyarrhythmias. It compares the shape of each QRS complex during a fast ventricular rate to a stored template. If enough events occur that match this template, Wavelet withholds detection. See “Enhancing detection with Wavelet” on page 107.

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 94.

Onset criterion – The Onset criterion is designed to prevent detection of sinus tachycardia as VT by requiring that a rapid increase in ventricular rate occurs before VT events can be classified. See “Details about Onset” on page 117.

High Rate Timeout – High Rate Timeout can turn off detection enhancements (Wavelet, Onset, or Stability) if a high rate episode is longer than a programmed duration. See “Details about High Rate Timeout” on page 125.

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 138 and “Confirming VT or FVT after detection” on page 158.

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. For more information about connection pathways, see “Delivery pathway electrodes” on page 135.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

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

Bradycardia pacing

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 VOO pacing mode, and provides the OVO mode to disable pacing. See Chapter 8, “Treating bradycardia” on page 169.

EP studies

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 66.

Quick reference

New and enhanced features

Maximo VR 7232Cx, 7232B, 7232E Reference manual

System overview 38

Indications and usage 41

Contraindications 41

Patient screening 41

The Maximo VR system2

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 2

System overview

The Model 7232 Maximo VR Single 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 ventricular leads. It then analyze s 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 a bipolar pacing/sensing lead (or paired unipolar

pacing/sensing leads) in the ventricle 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 sense cardiac activity and deliver pacing stimuli.

■

Programmer and software

The Medtronic programmer and Model 9979 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 VR 7232Cx, 7232B, 7232E Reference manual

The Maximo VR system

System overview

The Maximo VR devices and Model 9979 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 VR 7232Cx, 7232B, 7232E Implant Manual, which accompanies each device.

■

basic programmer and software desktop functions that are not included in Chapter 10, “Using the programmer” on page 197, 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 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 VR 7232Cx, 7232B, 7232E Reference manual

Chapter 2

System overview

You can use the Wavelet, Stability and Onset criteria to help the ICD distinguish between true ventricular arrhythmias and rapidly conducted supraventricular tachycardia (SVT) and withhold therapy for SVT.

Treating bradycardia

The ICD provides rate responsive ventricular pacing to treat bradycardia. 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 VR 7232Cx, 7232B, 7232E Reference manual

Indications and usage

The implantable cardioverter defibrillator is intended to provide ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life threatening ventricular arrhythmias.

Contraindications

The Maximo VR system is contraindicated for

■

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

■

patients with incessant VT or VF

■

patient who have a unipolar pacemaker

■

patients whose primary disorder is bradyarrhythmias or atrial arrhythmias.

The Maximo VR 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 VR 7232Cx, 7232B, 7232E Reference manual

Emergency therapy3

Delivering emergency therapies 44

How to deliver emergency 35 joule defibrillation 46

How to deliver emergency cardioversion 47

How to deliver emergency fixed burst pacing 48

How to deliver emergency VVI pacing 50

Maximo VR 7232Cx, 7232B, 7232E 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 VR 7232Cx, 7232B, 7232E 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 49).

Maximo VR 7232Cx, 7232B, 7232E 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

* Medtronic nominal setting

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 35 joule defibrillation

10, 11, …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. 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 VR 7232Cx, 7232B, 7232E 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 159.

Parameters

* Medtronic nominal setting

Emergency therapy

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

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 VR 7232Cx, 7232B, 7232E 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

* Medtronic nominal setting

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

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 VR 7232Cx, 7232B, 7232E 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. 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 mode

VVI

provided during emergency VVI pacing.

Lower Rate – Minimum pacing rate to maintain

70 ppm

adequate heart rate during periods of inactivity.

V. Amplitude – Voltage of the ventricular pacing

pulses delivered during emergency VVI pacing.

V. P u l se W i d t h – Duration of the ventricular pacing

1.6 ms

pulses delivered during emergency VVI pacing.

V. Pace Blanking – Time interval during which

320 ms

sensing is disabled after a pacing pulse.

Hysteresis – Enables tracking of intrinsic heart

Off 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 pacing rate to

Off 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 VR 7232Cx, 7232B, 7232E 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: 8 V

■

V. Width: 1.6 ms

■

V. Pace Blanking: 320 ms

■

Hysteresis: Off

■

Ventricu l a r R a te

)

Stabilization: Off

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

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Part II

Device implant and patient follow-up procedures

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Implanting the ICD4

Overview 54

Preparing for an implant 54

Replacing an ICD 57

Positioning the leads 58

Testing sensing and pacing thresholds 60

Connecting the leads to the ICD 61

Testing defibrillation operation and effectiveness 65

Positioning and securing the ICD 67

Completing the implant procedure 68

Maximo VR 7232Cx, 7232B, 7232E 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 9978/9979 software application

■

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

■

external defibrillator

Maximo VR 7232Cx, 7232B, 7232E 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

Implanting the ICD

Preparing for an implant

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 4

Preparing for an implant

How to prepare for implanting

Set up the programmer and start the application

Preprogram the device

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

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

2. Install the Maximo VR Model 9979 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.

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 device and print a full summary report. Note: The If the programmer reports that an electrical reset occurred,

do not implant the device. Contact a Medtronic representative.

3. Confirm that the battery voltage displayed on the Quick Look screen is at least 3.0 V at room temperature

(see page 233).

4. Set up data collection parameters and the device internal clock (see page 251).

5. Perform a manual capacitor formation (see page 303).

■

Dump any charge on the capacitors.

■

Perform a test charge to full energy.

■

Retrieve the charge data.

■

Do not dump the stored charge. Allow it to dissipate, thus reforming the capacitors.

■

If the reported charge time is clinically unacceptable, contact a Medtronic representative.

6. Program the therapy and pacing parameters to values appropriate for the patient (see page 172 ). Ensure that all tachyarrhythmia detection is programmed Off (see page 80).

7. Interrogate the device again.

If the device has been exposed to lower temperatures or has delivered a recent high-voltage charge, the battery voltage may be temporarily lower than 3.0 V.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

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:

■

Notes:

■

Implanting the ICD

Replacing an ICD

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.

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 device free from the pocket. Be careful not to nick or breach the lead insulation.

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

4. Remove the device from the surgical pocket.

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

6. Measure sensing, pacing, and defibrillation efficacy using the replacement device.

7. Evaluate the defibrillation efficacy of the replacement system.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 4

Positioning the leads

Using transvenous 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 VR 7232Cx, 7232B, 7232E Implant Manual). Transvenous or epicardial leads may be used.

Use standard transvenous implant techniques to position the ventricular lead tip in the right ventricular apex.

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.

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.

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:

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Surgical incisions

Implanting the ICD

Positioning the 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.

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 VR 7232Cx, 7232B, 7232E Reference manual

Chapter 4

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 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.

Tab le 4- 1. Sensing and pacing values at implant

Measurement Acute Transvenous Leads Chronic Leads

R- wave amplitude ≥ 5 mV ≥ 3 mV

Ventricular slew rate: ≥ 0.75 V/s ≥ 0.5 V/s

Ventricular capture threshold:

At 0.5 ms pulse width

Considerations

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

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.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

≤ 1.0 V ≤ 3.0 V

Connecting the leads to the ICD

For more detailed information about lead/connector compatibility, see the Maximo VR 7232Cx, 7232B, 7232E Implant Manual, or contact Medtronic Technical Services at 1-800-723-4636.

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

Tabl e 4-2 . Cx-type connector characteristics

General description Device

One IS-1 connector for pacing and sensing, Two DF-1 connectors for high-voltage therapy, Active Can electrode (programmable)

Implanting the ICD

Connecting the leads to the ICD

Port

SVC DF-1 HVX

RV DF-1 HVB

Can — HVA, Can

V IS-1 bipolar

Connector Typ e

Software Name

Figure 4-1. Cx-type connector

1 Suture holes

2 SVC port (DF-1)

3RV port (DF-1)

4 Programmable Active Can

5V port (IS-1)

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 4

Connecting the leads to the ICD

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

Tab le 4- 3. B-type connector characteristics

General description Device

Three 6.5 mm unipolar high-voltage ports and one

3.2 mm low profile bipolar pace/sense (IS-1 compatible) port.

The HVA and HVX ports are electrically connected and are treated as the HVX electrode. For more information, see “B- and E-type connector pathways” on page 136.

Figure 4-2. B-type connector

Port

Connector Typ e

Software Name

HVB 6.5 mm HVB

HVA

HVX

6.5 mm HVX

Can — HVA, Can

P/S bipolar pace

3.2 mm bipolar (IS-1 compatible)

sense

1 Suture holes

2 HVB port (6.5 mm)

3 HVA port (6.5 mm)

4 Programmable Active Can

5 HVX port (6.5 mm)

6 P/S port (3.2 mm)

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Implanting the ICD

Connecting the leads to the ICD

Tabl e 4-4 . E-type connector characteristics

General description Device

Port

P+/S 5.0 mm

Two 6.5 mm unipolar high-voltage ports and two 5 mm unipolar pace/sense ports.

HVA 6.5 mm HVX

HVB 6.5 mm HVB

Can — HVA, Can

P-/S 5.0 mm

The HVA port of the E-type connector can be used as the HVX electrode when Active Can is programmed off. For more information, see “B- and E-type connector pathways” on page 136.

Figure 4-3. E-type connector

Connector Typ e

Software Name

1 Suture holes

2 P+/S port (5.0 mm)

3 HVA port (6.5 mm)

4 Programmable Active Can

5 HVB port (6.5 mm)

6 P-/S port (5.0 mm)

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 4

Connecting the leads to the ICD

How to connect the lead to the device

30SetScrew.eps

30LeadTIp.eps

Model 7232Cx connector shown in example

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.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Implanting the ICD

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 330.

High-voltage implant values

Measured values must meet the following requirements at implant.

Tabl e 4-5 . High-voltage therapy values at implant

Measurement Acute or Chronic Leads

V. Defib impedance

SVC (HVX) impedance (if applicable)

Defibrillation threshold

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

20 - 200 ohms

≤ 25 J

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 299.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

to verify the defibrillation

Chapter 4

Testing defibrillation operation and effectiveness

How to perform defibrillation threshold testing

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 VR 7232Cx, 7232B, 7232E Reference manual

Implanting the ICD

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

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

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 4

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

3. Program patient information. See “How to view and enter new patient information” on page 282.

4. Configure the Patient Alert feature. See “Using the Patient Alert feature” on page 235.

5. Set up data collection parameters. See “Setting up data collection” on page 249.

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

7. 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 307.

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

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Conducting a patient follow-up

Patient follow-up guidelines 70

Verifying the status of the implanted system 70

Verifying accurate detection and appropriate therapy 71

Verifying effective bradycardia pacing 73

session

Maximo VR 7232Cx, 7232B, 7232E 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 243) 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 26). 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 190).

– 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 274) for information on this new report.

Maximo VR 7232Cx, 7232B, 7232E 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 299).

■

Perform an EGM Amplitude test for comparison to previous EGM Amplitude measurements. See (“How to perform an EGM Amplitude test” on page 302).

■

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 233).

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 260).

■

Check stored SVT episode records for appropriate identification of SVTs.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 5

Verifying accurate detection and appropriate therapy

Considerations

Review the following information before verifying detection and therapy.

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

Episode misidentification – If the episode records indicate that false detections have occurred, the Sensing Integrity counter may help in determining the prevalence of oversensing. For more information, see (“Sensing integrity counter” on page 256).

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 81).

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 96).

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 Wavelet” on page 107), (“Enhancing VT detection with the Onset criterion” on page 116), and (“Enhancing VT detection with the Stability criterion” on page 121).

Maximo VR 7232Cx, 7232B, 7232E 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 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 Cardiac Compass report for comparison to patient history (see page 274 ).

■

Conduct a pacing threshold test (see page 294) to verify that the programmed pacing parameters provide a sufficient safety margin.

Considerations

Review the following information before verifying bradycardia pacing.

Ventricular Pacing – If the ventricle is predominantly paced and the patient exhibits adequate ventricular response, consider decreasing the Lower Rate.

% Pacing – Because the percentages for this counter are rounded to the nearest unit, they may not add up to 100%.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Part III

Configuring the ICD for the patient

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Detecting tachyarrhythmias6

Detection overview 78

Setting up sensing 81

Detecting VF episodes 85

Detecting VT episodes 90

Detecting FVT episodes 96

Detecting tachyarrhythmia episodes with Combined Count 101

Monitoring episodes for termination or redetection 104

Enhancing detection with Wavelet 107

Enhancing VT detection with the Onset criterion 116

Enhancing VT detection with the Stability criterion 121

Detecting prolonged tachyarrhythmias with High Rate Timeout 124

Key terms 126

Maximo VR 7232Cx, 7232B, 7232E 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 the Wavelet Dynamic Discrimination criterion, the Onset criterion, and the Stability criterion.

Figure 6-1 shows how all of these detection features interact during initial detection. During redetection, the device does not apply the Wavelet and Onset 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 88.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Detecting tachyarrhythmias

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

Detection overview

Ye s

No / suspended by High Rate Timeout

Update counts and pattern information

Has High Rate Timeout suspended detection

Is the Onset criterion allowing VT event counting? (VT and

Does Stability reset the VT event count?

Ventricular Event

Is the interval in the

VF, FVT, or VT detection zone?

Ye s

enhancements?

FVT via VT detection only)

Ye s

(VT and FVT via VT detection only)

Has a tachyarrhythmia event count

reached an NID?

Ye s

Is Wavelet on?

Ye s

Tachy

Episode

Detected

Ye s

Is the median ventricular interval less than the

SVT Limit?

Is Wavelet withholding detection?

Ye s

Maximo VR 7232Cx, 7232B, 7232E Reference manual

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, Wavelet, 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 101) 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 126).

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Setting up sensing

The device provides bipolar sensing in the ventricle via the sensing electrodes of the implanted ventricular lead. You can adjust the sensitivity to intracardiac signals using the ventricular sensitivity setting. This setting defines the minimum electrical amplitude recognized by the device as a ventricular sensed event.

Proper sensing is essential for the safe and effective use of the device. To provide appropriate sensing, the device uses an auto-adjusting ventricular sensing threshold.

See “Details about sensing” on page 83.

Parameters

V. Sensitivity (mV) – Minimum amplitude of

electrical signal that registers as a sensed ventricular event.

Considerations

Detecting tachyarrhythmias

Setting up sensing

* Medtronic nominal setting

0.15, 0.3*, 0.45, 0.6,

0.9, 1.2

Review the following information before programming sensing parameters.

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

Bradycardia pacing and sensing – A combination of high pacing pulse width or high amplitude with a low sensitivity threshold may cause inappropriate sensing. 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 ventricula r sensitivity threshold of 0.3 mV is recommended to maximize the probability of detecting VF and to limit the possibility of oversensing.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 6

Setting up 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 and oversensing.

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

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.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

How to program sensitivity

Details about sensing

Auto-adjusting sensitivity thresholds

Detecting tachyarrhythmias

Setting up sensing

1. Select Params > Detection

2. Select the desired V. Sensitivity parameter value.

3. Select [PROGRAM].

The device automatically adjusts the sensitivity thresholds after certain paced and sensed events to help reduce oversensing from T-waves and pacing. Figure 6-2 shows how sensitivity thresholds are adjusted after different types of events.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 6

Setting up sensing

Figure 6-2. Auto-adjusting sensitivity threshold

Sensitivity threshold

1 2

Rectified and Filtered

V. E G M

Marker Channel

30Autoadjust.eps

V S

V P

1 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).

2 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.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Detecting tachyarrhythmias

Detecting VF episodes

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 ventricular depolarizations.

Table 6-1 shows the duration of the fixed blanking periods. For information on programmable pace blanking periods (see page 186).

Tabl e 6-1 . Fixed blanking periods

Ventricular blanking after sensed ventricular event 120 ms

Ventricular blanking after delivered cardioversion or defibrillation therapy

Refractory periods

During a refractory period, the device senses normally, but classifies sensed events as refractory and limits its response to these events. Refractory periods are used during synchronization to help prevent the device from delivering cardioversion and defibrillation therapies at inappropriate times. See “Synchronizing defibrillation without confirming VF” on page 137 and “Synchronizing cardioversion after charging” on page 159.

Note: Refractory periods do not affect tachyarrhythmia detection.

Detecting VF episodes

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

See “Details about VF detection” on page 88.

520 ms

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Chapter 6

Detecting VF episodes

Parameters

* Medtronic nominal setting

Considerations

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.

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

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.

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Restrictions

Detecting tachyarrhythmias

Detecting VF episodes

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 Wavelet – You can program the device to exclude rapidly conducted SVTs from VF detection by enabling the Wavelet Dynamic Discrimination criterion. Note that the SVT Limit must be programmed shorter than the VF Interval in order for Wavelet to affect VF detection. See “Enhancing detection with Wavelet” on page 107.

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 364).

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 VR 7232Cx, 7232B, 7232E Reference manual

Chapter 6

Detecting VF episodes

How to program VF detection

Details about VF detection

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].

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).

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 101).

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Figure 6-3. Device detects VF

ECG

Marker Channel

Detecting tachyarrhythmias

Detecting VF episodes

1 2 3

FSFSFSFSFSFSFSFSFSF

VSVSV

VF Event Count

V S

FSFSF

V S

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

30VFDetection.eps

Maximo VR 7232Cx, 7232B, 7232E 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 92.

* Medtronic nominal setting

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

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.

On, Off*, or Monitor

280, 290, …400*, …600

12, 16*, …52, 76, 100

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

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Considerations

Detecting tachyarrhythmias

Detecting VT episodes

Review the following information before programming VT detection parameters.

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

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

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 101.

VT detection and rapidly conducted SVTs – You can program the device to exclude rapidly conducted SVTs from VT detection by enabling the Wavelet, Onset, or Stability detection criteria. See “Enhancing detection with Wavelet” on page 107, “Enhancing VT detection with the Onset criterion” on page 116, and “Enhancing VT detection with the Stability criterion” on page 121.

Restrictions

Review the following information before programming VT detection parameters.

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

Maximo VR 7232Cx, 7232B, 7232E 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 101).

Maximo VR 7232Cx, 7232B, 7232E Reference manual

Figure 6-4. Device detects VT

ECG

Marker Channel

132

Detecting tachyarrhythmias

Detecting VT episodes

VT Event Count

V S

VSV

T S

10123456

TSTSTSTSTST

VT Interval

ECG

Marker Channel

T D

V S

30VTDetection.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 than 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 VR 7232Cx, 7232B, 7232E 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.

Wavelet, Onset, and Stability criteria – Before the device detects a tachyarrhythmia episode, the Wavelet, Onset, 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 Wavelet as initial VF or FVT detection begins. However, since Stability and Onset do not affect either VF detection or FVT via VF detection, they are 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 VR 7232Cx, 7232B, 7232E Reference manual

Figure 6-5. Device detects and monitors VT

ECG

Marker Channel

Detecting tachyarrhythmias

Detecting VT episodes

2 31

TSTSTSTDTSTST

13 14 15 16 0 0 0

30VTMonitor.eps

200 ms

VT Event Count

VT Interval

V S

VSTSTSTST

1234

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 VR 7232Cx, 7232B, 7232E 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 98.

* Medtronic nominal setting

Considerations

FVT Detection Enable – Enables FVT

detection via the VF or the VT detection algorithm.

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

Off*, via VF, or via VT

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 VR 7232Cx, 7232B, 7232E 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 Wavelet – You can program the device to exclude rapidly conducted SVTs from FVT detection by enabling the Wavelet detection criterion. Note that the SVT Limit must be programmed shorter than the VF Interval for Wavelet to affect FVT via VF detection. See “Enhancing detection with Wavelet” on page 107.

Restrictions

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 364.

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 VR 7232Cx, 7232B, 7232E 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 VR 7232Cx, 7232B, 7232E 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 101).

Figure 6-6. Device detects FVT via VF

Detecting tachyarrhythmias

Detecting FVT episodes

1 2

ECG

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.

30FVTDetect.eps

200 ms

Maximo VR 7232Cx, 7232B, 7232E Reference manual

100

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 VR 7232Cx, 7232B, 7232E Reference manual

Medtronic 7232CX 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 VR 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