Medtronic 7231CX Reference Guide

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GEM®III VR 7231

Implantable Cardioverter Defibrillator

System Reference Guide

GEM® III VR System Reference Guide

A guide to the operation and programming of the 7231 GEM®III VR Implantable Cardioverter Deﬁbrillator

GEM, Marker Channel, Decision Channel, T-Shock, Quick Look, QuickLink, Patient Alert, Active Can, and Flashback are trademarks of Medtronic, Inc.

Table of Contents

Introduction vii Abbreviations and Acronyms ix

1. Quick Reference

Primary Capabilities 1-2 Physical Characteristics 1-5 Electrical Characteristics 1-6 Magnet Application 1-10 Emergency Settings 1-11 Programmable Parameters Overview 1-12 Detection Parameters 1-13 Therapy Parameters 1-14 Bradycardia Pacing Parameters 1-16 Automatic Capacitor Formation Parameters 1-17 Data Collection Parameters 1-18 Patient Alert™ Monitoring System Parameters 1-19 Patient Information Parameters 1-20 EP Studies Parameters 1-21 Fixed Parameters 1-23 Notes 1-24

2. Emergency Therapy

Overview 2-2 Effect on System Operation 2-3 On-Screen and Display Panel Buttons 2-3 Emergency Deﬁbrillation 2-4 Emergency Cardioversion 2-5 Emergency Fixed Burst Pacing 2-6 Emergency VVI Pacing 2-7

3. Overview

System Description 3-2 Detection and Therapy Overview 3-4

4. Tachyarrhythmia Detection

Sensing 4-2 VF Detection 4-5 VT Detection 4-8 Combined Count Detection 4-11 VT Stability Option 4-13 EGM Width Criterion 4-15

GEM®III VR System Reference Guide

iii

Table of Contents

FVT Detection 4-21 Termination and Redetection 4-26

5. Tachyarrhythmia Therapies

High Voltage Therapy Overview 5-2 Deﬁbrillation 5-9 Cardioversion 5-15 Antitachycardia Pacing Therapy Overview 5-20 Programming ATP Therapies 5-22 Burst Pacing 5-24 Ramp Pacing 5-26 Ramp+ Pacing 5-28 Smart Mode 5-30 Progressive Episode Therapies 5-33

6. Bradycardia Pacing

Pacing Mode 6-2 Bradycardia Pacing Parameters 6-4 Post Shock Pacing Parameters 6-8 Rate Responsive Pacing 6-11 Hysteresis 6-17 Ventricular Rate Stabilization 6-20

7. Programmer and Software

Connecting the Programmer Hardware 7-2 Setting Up and Using the Programmer 7-12 Using the Programmer Display Screen 7-22 Starting a Patient Session 7-30 Programming Parameter Values 7-32 Checklist 7-35 Live Rhythm Monitor 7-42 Recording Live Waveforms 7-54 Printing Reports 7-61 Changes This Session 7-66 Ending a Patient Session 7-67

8. Conducting System Tests

System Tests Overview 8-2 Underlying Rhythm Test 8-3 Pacing Threshold Test 8-4 Lead Impedance Test 8-6 EGM Width Test 8-9 Manual EGM Amplitude Test 8-14 Test Charge / Dump 8-16

GEM®III VR System Reference Guide

Capacitor Formation 8-18

9. EP Studies

EP Studies Overview 9-2 Delivering Inductions 9-6 T-Shock™ 50 Hz Burst Induction 9-9 Manual Burst Induction 9-10 PES Induction 9-11 Delivering Manual Therapies 9-12 Manual Deﬁbrillation Therapy 9-13 Manual Cardioversion Therapy 9-14 Manual ATP (Antitachycardia Pacing) Therapies 9-14

10. Data Collection

Data Collection Overview 10-2 Quick Look™ 10-4 Setting Up Data Collection 10-6 Counter Data 10-11 Episode Data 10-15 Patient Information 10-28 Battery and Lead Measurements 10-32 Device Status Indicators 10-36 Saving and Retrieving ICD Data 10-38

Induction 9-8

Table of Contents

11. Patient Alert™ Monitoring System

Patient Alert™ Setup 11-2 Instructions for the Patient 11-7 Instructions for Clinic Personnel 11-9 Patient Alert™ Event Log 11-10

12. Implant and Follow-up

Pre-Implant Information 12-2 Operative Set-Up 12-4 Surgical Approach 12-6 Sensing and Pacing Measurements 12-8 Deﬁbrillation Testing 12-9 Placing the ICD 12-15 Replacing the ICD 12-16 Pre-Discharge Evaluation 12-18 Follow-Up Recommendations 12-19

A. Appendix A - Warnings and Precautions

General Warnings A-2

GEM®III VR System Reference Guide

Table of Contents

Sterilization, Storage, and Handling A-3 Implantation and ICD Programming A-4 Lead Evaluation and Lead Connection A-5 Follow-up Testing A-6 ICD Explant and Disposal A-7 Environmental and Medical Therapy Hazards A-7 Home and Occupational Environments A-9

B. Appendix B - Parameter Interlocks

Bradycardia Pacing Parameter Interlocks B-2 Detection Parameter Interlocks B-3 Resolving Tachy / Brady Parameter Interlocks B-4

G. Glossary

I. Index

GEM®III VR System Reference Guide

Introduction

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.

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.

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.

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.

GEM®III VR System Reference Guide

vii

Introduction

References

Automatic deﬁbrillation was invented and patented in 1953 by Dr. F. Zacouto, who designed an external device that delivered a deﬁbrillation impulse to the heart upon detection of very rapid ECG activity in combination with the absence of arterial pulsations.

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

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

Futura Publishing Co. 1994.

■

Singer I, Barold SS, Camm AJ, Eds.

Nonpharmacological Therapy of

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

Futura Publishing Co. 1998.

■

Estes M, Manolis AS, Wang P, Eds.

Cardioverter-Deﬁbrillators

■

Kroll MW, Lehmann MH, Eds.

. New York, NY: Marcel Dekker, Inc. 1994.

Therapy: The Engineering-Clinical Interface

Implantable

Implantable Cardioverter-Deﬁbrillator

. Norwell, MA: Kluwer

Academic Publishers 1996.

Cardiac

. Armonk, NY:

viii

Notice

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.

GEM®III VR System Reference Guide

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

FVT Fast Ventricular Tachycardia

ICD Implantable Cardioverter-Deﬁbrillator

J joules

-1

min

ms milliseconds

mV millivolts

NID Number of Intervals to Detect

PES Programmed Electrical Stimulation

POR Power On Reset

ppm paces or pulses per minute

PVC Premature Ventricular Contraction

RCNID Combined (VT and VF) Number of Intervals to Redetect

RNID Number of Intervals to Redetect

RR R-R interval; a ventricular interval

SVT Supraventricular Tachycardia

TDI Tachycardia Detection Interval

V volts

V- Ventricular

VF Ventricular Fibrillation

VF NID VF Number of Intervals to Detect

VF RNID VF Number of Intervals to Redetect

reciprocal minutes; for example, pacing pulses per minute

Abbreviations and Acronyms

GEM®III VR System Reference Guide

Abbreviations and Acronyms

VRS Ventricular Rate Stabilization

VT Ventricular Tachycardia

VT NID VT Number of Intervals to Detect

VT RNID VT Number of Intervals to Redetect

GEM®III VR System Reference Guide

Quick Reference

Primary Capabilities 1-2

Physical Characteristics 1-5

Electrical Characteristics 1-6

Magnet Application 1-10

Emergency Settings 1-11

Programmable Parameters Overview 1-12

Detection Parameters 1-13

Therapy Parameters 1-14

Bradycardia Pacing Parameters 1-16

Automatic Capacitor Formation Parameters 1-17

Data Collection Parameters 1-18

Patient Alert™ Monitoring System Parameters 1-19

Patient Information Parameters 1-20

EP Studies Parameters 1-21

Fixed Parameters 1-23

Notes 1-24

GEM®III VR System Reference Guide

1-1

Quick Reference

Primary Capabilities

Pacing Management

Rate responsive bradycardia pacing up to 150 ppm (min-1): VVIR and VVI modes

Ventricular Rate Stabilization after short ventricular intervals

Single chamber hysteresis

Tachyarrhythmia Detection

Ventricular ﬁbrillation and ventricular tachycardia detection (VF, VT, and FVT)

Single chamber VT Stability criterion

Single chamber EGM Width criterion

Tachyarrhythmia Therapy

1-2

Up to six (each) automatic VF, VT, and FVT therapies

Ventricular deﬁbrillation and cardioversion, 30 joules delivered (35 joules stored) with 50% tilt

Burst, Ramp, and Ramp+ antitachycardia pacing

Smart Mode disables ineffective ATP therapies

Progressive Episode Therapies ensures increasingly aggressive therapy sequencing

Patient Management

Audible Patient Alert™ monitoring system

Automatic, painless pacing and HV lead impedance testing

Programmer-assisted EGM Amplitude Test

Lead performance trend report and display

Sensing integrity counter

GEM®III VR System Reference Guide

Quick Reference

Primary Capabilities

Patient information that can be entered, viewed and printed via the programmer

Two simultaneous real time EGMs: ventricular / far-ﬁeld

Two channels stored EGM: ventricular / far-ﬁeld

Marker Channel™ telemetry

Supplementary Decision Channel™ annotations in stored EGM and on real time recordings that indicate detection algorithm status.

256 Kbyte data storage, including two EGMs, Markers, and Flashback™ Memory of V-V intervals

Save-to-Disk and Read-from-Disk patient data features

Table 1-1. GEM®III VR ICD Data Collection Summary

Tachy episodes

SVT/NST episodesa50 SVT/NST episodes: text, stored EGM, intervals,

EGM capacity 12 minutes (2 channels) or 22 minutes (1 channel)

EGM sources Four options: ventricular / far-ﬁeld

EGM options Store before onset; Store during charging

Flashback™ Memory

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

Episode counters - VF, FVT, and VT

Therapy Efﬁcacy Counters

Patient Alert™ Events

All tachy, NST, and SVT episode data are stored in the same block of memory.

For VT or SVT episodes, when EGM Width criterion is On or Passive.

150 VF/VT/FVT episodes: text, stored EGM, intervals, QRS Snapshot

QRS Snapshotb, and episode summaries (typically, only episode summaries are provided for NSTs)

1000 intervals before interrogation, latest VF, and latest VT

- Non-sustained tachy episodes and SVTs

- Percentage paced/sensed rhythm

- Single PVCs and PVC runs

- Rate stabilization pulses and runs

Counts for each VF, FVT, VT Therapy:

- Delivered

- Successful

- Unsuccessful

- Intervention Total number of aborted shocks

Up to 10 log entries: text and date for the ﬁrst time an alert is triggered between clearing the log entries.

GEM®III VR System Reference Guide

1-3

Quick Reference

Primary Capabilities

Other features

Direct replacement for DF-1 / IS-1 systems, including all Medtronic “C,” “Cx,” and “D” ICDs

Medtronic icon-based user interface

Full-size report printing

Quick Look™ programming summary with Quick Links™ to stored episodes and observations

Non-invasive EP study functions: ventricular inductions / manual therapies

Smart Auto Cap Formation extends the formation timer after therapeutic charging

Auto-Resume feature automatically resumes detection after an induction

Checklist feature provides streamlined, customizable navigation through sets of tasks for follow-up and implant visits

1-4

GEM®III VR System Reference Guide

Physical Characteristics

Volume 39.2 cc

Mass 77.4 g

H x W x D

Surface area of device can 69 cm

Quick Reference

Physical Characteristics

69.3 mm x 50.8 mm x 13.5 mm

Radiopaque ID

Materials in contact with human tissue

PJL

Titanium / polyurethane / silicone rubber

Battery Lithium silver vanadium oxide

Connector conﬁguration One IS-1 connector for pacing and sensing,

Two DF-1 connectors for high voltage therapy, Active Can® electrode

SVC

(HVX)

IS-1 V

DF-1

(HVB)

Can (HVA)

This measurement refers to the thickness (depth) of the can; grommets may protrude slightly beyond 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.

GEM®III VR System Reference Guide

1-5

Quick Reference

Electrical Characteristics

Longevity

Table 1-2 below provides longevity estimates based on accelerated battery discharge data and device modeling with 60 ppm (min-1) pacing

rate, 2 V pacing pulse amplitude, 0.6 ms pacing pulse width, and 30 J delivered therapy energy

Table 1-2. GEM®III VR Projected Longevity in Years with 2 V Pacing Pulse

Percent pacing

0% Semi-Annual 8.9 8.9

15% Semi-Annual 8.6 8.7

50% Semi-Annual 8.2 8.5

100% Semi-Annual 7.6 8.1

Maximum Energy Charging Frequency

Quarterly 7.8 7.8

Quarterly 7.5 7.6

Quarterly 7.2 7.4

Quarterly 6.8 7.2

Amplitude and 0.6 ms Pacing Pulse Width

500 ohm pacing

impedance

900 ohm pacing

impedance

1-6

Table 1-3 below provides longevity estimates based on accelerated battery discharge data and device modeling with 60 ppm (min-1) pacing

rate, 3 V pacing pulse amplitude, 0.4 ms pacing pulse width, and 30 J delivered therapy energy

Table 1-3. GEM®III VR Projected Longevity in Years with 3 V Pacing Pulse

Percent pacing

0% Semi-Annual 8.9 8.9

15% Semi-Annual 8.4 8.5

50% Semi-Annual 7.5 8.0

100% Semi-Annual 6.5 7.4

EGM pre-storage feature set to Off.

Maximum Energy Charging Frequency

Quarterly 7.8 7.8

Quarterly 7.4 7.5

Quarterly 6.7 7.0

Quarterly 6.0 6.6

GEM®III VR System Reference Guide

Amplitude and 0.4 ms Pacing Pulse Width

500 ohm pacing

impedance

900 ohm pacing

impedance

Quick Reference

Electrical Characteristics

The following factors result in decreased longevity:

■

an increase in pacing rate, pacing amplitude or pulse width, the ratio of bradycardia paced to sensed events, or the charging frequency,

■

a decrease in pacing impedance, or

■

using the pre-onset EGM storage feature or Holter telemetry.

To maximize ICD longevity:

■

Optimize pacing rate and output parameters for the patient.

■

Set the delivered energy value for the ﬁrst programmed high voltage therapy to a value lower than maximum energy.

■

Set the automatic capacitor formation interval to a longer value (unless a shorter interval is required to maintain clinically acceptable charge times).

■

Use the pre-onset EGM storage feature and Holter telemetry only for short periods of time.

Battery Voltage

Battery voltage appears on the programmer display and on printed reports. See “Preparing the ICD for Implant” on page 12-5, and “Replacement Indicators” on page 12-20 for more information.

Table 1-4. Battery Voltage Indicators

Elective Replacement (ERI)

≤ 2.55 V

Pacing mode and rate (magnet and non-magnet) as programmed

End of Life (EOL)

≤ 2.40 V

Pacing mode and rate (magnet and non-magnet) as programmed

The minimum time between ERI and End of Life is three months, assuming 100% VVI pacing at 60 ppm (min

When the battery reaches EOL, immediate replacement is recommended. (See also “Charge Circuit Timeout” on page 5-4.)

-1

), 3 V, 0.4 ms; 500 Ω pacing load; and six 30 J charges.

GEM®III VR System Reference Guide

1-7

Quick Reference

Electrical Characteristics

Charge Time

The high voltage capacitors charge more rapidly just following a capacitor formation, when they are fully formed. Between formations, the capacitors gradually deform, resulting in longer charge times toward the end of the formation interval. See page 8-18 for information on managing charge time. See page 8-17 for instructions on using the Test Charge feature to measure charge time. Table 1-5 provides typical full energy charge times at BOL and ERI based on the time interval since the last capacitor formation. A full energy charge is any charge to full energy (either via a capacitor formation or therapy delivery).

Table 1-5. Typical Full Energy (30 J Delivered) Charge Times

Capacitors

fully formed

At Beginning of Life (BOL) 6 seconds ≈ 1 second

Near Elective Replacement Indicator (ERI)

Typical values for stated conditions, actual charge time performance may vary.

14 seconds ≈ 1 seconds

1 month after

capacitor

formation

longer than fully formed

6 months after

capacitor

formation

≈ 2 seconds longer than fully formed

≈ 5 seconds longer than fully formed

1-8

GEM®III VR System Reference Guide

Quick Reference

Electrical Characteristics

High Voltage Therapy Energy

Table 1-6 compares delivered energy levels to energy levels stored by the device.

Note: 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 1-6. Comparing Programmed (Actual Delivereda) and Storedb Energy Levels

Programmed

(Actual Delivered)

Energy (J)

0.4 0.5 .09 9 11 1.94

0.6 0.8 .13 10 12 2.16

0.8 1.0 .17 11 13 2.38

1.0 1.2 .22 12 14 2.59

1.2 1.5 .26 13 15 2.81

1.4 1.7 .30 14 16 3.02

1.6 2.0 .35 15 18 3.24

1.8 2.2 .39 16 19 3.46

2 2.4 .43 18 21 3.89

3 3.6 .65 20 24 4.32

4 4.7 .86 22 26 4.75

5 5.9 1.08 24 28 5.18

6 7.1 1.30 26 31 5.62

7 8.3 1.51 28 33 6.05

8 9.4 1.73 30 35 6.48

Energy and voltage delivered at connector block into a 75 ohm load.

Energy stored at end of charge on capacitor.

Typical charge time at BOL, with fully formed capacitors.

Stored

Energy (J)

Charge

Timec (sec)

Programmed

(Actual Delivered)

Energy (J)

Stored

Energy (J)

Charge

Timec (sec)

GEM®III VR System Reference Guide

1-9

Quick Reference

Magnet Application

Applying a magnet closes a reed switch within the ICD (see Table 1-7 for magnet effects). When the magnet is removed, the ICD returns to its programmed operations.

Pacing Mode as programmed

Pacing Rate and Interval as programmed

VF, VT, and FVT Detection and Therapy

Patient Alert™ Audible Tones

The programming head contains a magnet which can suspend detection. However, if the Resume option has been enabled via the programmer, detection will remain enabled.

The alert sounds only if Patient Alert™ is programmed On for any alert except POR. A POR alert causes an alarm every 20 hours, even if Patient Alert is programmed Off.

Table 1-7. Effects of Magnet Application

suspended

(30 seconds or less) continuous tone (Alarm OK) on/off intermittent tone (seek follow-up) high/low dual tone (urgent follow-up)

1-10

GEM®III VR System Reference Guide

Emergency Settings

The table below lists the values that can be selected for the ICD emergency therapy parameters. Default values are highlighted in

italicized

page 1-24.

Table 1-8. Emergency Therapy Parameters

Parameter Selectable Values (and

Deﬁbrillation

Energy (J) 10, 11, . . ., 16,

Pathway AX→B

Cardioversion

Energy (J) 0.4, 0.6, . . ., 1.8,

Pathway AX→B

Fixed Burst

Pacing Interval (ms) 100, 110, . . .,

Pulse Amplitude (V) 8

Pulse Width (ms) 1.6

text. The Notes column lists letters than correspond to notes on

18, 20, . . .,

2, 3, . . ., 16 18, 20, . . .,

360, 370, . . ., 600

350

default value

Quick Reference

Emergency Settings

bold,

) Notes

VVI Pacing

Pacing Mode VVI

Lower Rate (ppm, min-1)70

Vent. Rate Stabilization Off

Hysteresis Off

Sensitivity As programmed

Pulse Amplitude (V) 8 V

Pulse Width (ms) 1.6 ms

Pace Blanking (ms) 320 ms

Post Shock Pace Blanking (ms) 320 ms A.

GEM®III VR System Reference Guide

1-11

Quick Reference

Programmable Parameters Overview

The tables that follow (from “Detection Parameters” on page 1-13 to “Patient Information Parameters” on page 1-20) list the values that can be selected for all ICD programmable parameters. As applicable, these tables also indicate the Medtronic nominal value, the POR value, and the shipped value for each parameter.

Medtronic nominal values – are suggested settings for parameters under nominal conditions. Medtronic nominal values, if applicable, are indicated in the Programmable Values column with

POR values – are the values to which the ICD resets parameters after a power-on reset (POR). If a POR occurs, the ICD sounds a high-urgency Patient Alert™ tone every twenty hours. See the “Power-On Reset Recovery Procedure” on page 10-37.

Shipped values – are the programmed parameter values when the ICD is shipped from Medtronic.

The Notes column in each table lists letters that correspond to notes on page 1-24. These include exceptions or clariﬁcations that relate to the values listed in the programmable parameter tables.

bold, italicized

text.

1-12

GEM®III VR System Reference Guide

Quick Reference

Detection Parameters

Table 1-9. Detection Parameters

Parameter Programmable Values

VF DETECTION PARAMETERS

Detection Enable

Interval (ms) 240, 250, . . .,

Initial NID 12/16,

Redetect NID 6/8, 9/12,

V. Sensitivity (mV) 0.15,

FVT DETECTION PARAMETERS

Detection Enable

Interval (ms) 200, 210, . . ., 600 --- --- C, F.

V. Sensitivity (mV) 0.15,

(and

Medtronic Nominal

, Off On Off

320

330, 340, . . ., 400

18/24

12/16

0.3

, 0.45, 0.6,

0.3

, 0.45, 0.6,

, 24/32,

, 18/24,

30/40, 45/60, 60/80, 75/100, 90/120, 105/140, 120/160

21/28, 24/32, 27/36, 30/40

0.9, 1.2

Off

, via VF, via VT Off Off

0.9, 1.2

)

POR

Value

320 320 C.

18/24 18/24 B.

12/16 12/16

0.3 0.3 D, E.

Shipped

Value

Notes

VT DETECTION PARAMETERS

Detection Enable On,

Interval (ms) 280, 290, . . .,

Initial NID 12,

Redetect NID 4, 8, 12, . . ., 52 12 12

V. Sensitivity (mV) 0.15,

VT Stability Criterion Parameters

VT Stability (ms)

EGM WIdth Criterion Parameters

EGM Width Enable On, Passive,

Slew threshold (mV/sec) 18, 24, 30, . . ., 144 30 30

Width threshold (ms) 24, 28, 32, . . ., 80, . . ., 152 80 80

Off

400

410, 420, . . ., 600

, . . ., 52,

76, 100

0.3

0.9, 1.2

Off

, 0.45, 0.6,

, 30, 40, . . ., 100 Off Off C.

Off

Off Off

400 400 C.

16 16

0.3 0.3 D, E.

Off Off G.

GEM®III VR System Reference Guide

1-13

Quick Reference

Therapy Parameters

Table 1-10. Therapy Parameters (Sheet 1 of 2)

Parameter Programmable Values

VF THERAPY PARAMETERS

Therapy Status

Energy (J) 0.4, 0.6, . . ., 1.8,

Pathway

Reconﬁrm VF

VT and FVT THERAPY PARAMETERS

Cardioversion Therapy Parameters

Therapy Status

Energy (J) 0.4, 0.6, . . ., 1.8,

Pathway

(and

Medtronic Nominal

, Off On (all) On (all)

2, 3, . . ., 16, 18, 20, . . .,

AX→B

Yes

, Off --- ---

2, 3, . . ., 16, 18, 20, . . .,

AX→B

, B→AX AX→B (all) AX→B (all) I.

, No Yes Yes L.

, B→AX --- --- I.

)

POR

Value

30 (all) 30 (all) I, J, K.

--- --- I, K.

Shipped

Value

Notes

Burst Pacing Therapy Parameters

Therapy Status

Initial # Pulses 1, 2, . . ., 6, . . ., 15 --- --- I.

R-S1 Interval (% of R-R)

Pacing Interval Decrement (ms) 0,

# Sequences 1, 2, 3, . . ., 10 --- ---

Smart Mode On,

1-14

GEM®III VR System Reference Guide

, Off --- ---

50, 53, 56, 59, 63, 66, . . ., 84, 88, 91, 94, 97

, . . ., 40 --- ---

Off

--- --- I.

--- --- M.

Quick Reference

Therapy Parameters

Table 1-10. Therapy Parameters (Sheet 2 of 2)

Parameter Programmable Values

Ramp Pacing Therapy Parameters

Therapy Status

Initial # Pulses 1, 2, . . ., 8, . . ., 15 --- --- I, X.

R-S1 Interval (% of R-R)

Pacing Interval Decrement (ms) 0, 10, . . ., 40 --- --- I.

# Sequences 1, 2, 3, . . ., 10 --- ---

Smart Mode On,

Ramp+ Pacing Therapy Parameters

Therapy Status

Initial # Pulses 1, 2, 3, . . ., 15 --- --- I.

R-S1 Interval (% of R-R)

S1-S2 Interval (% of R-R)

S2-Sn Interval (% of R-R)

# Sequences 1, 2, . . ., 5, . . ., 10 --- ---

Smart Mode On,

(and

Medtronic Nominal

, Off --- ---

50, 53, 56, 59, 63, 66, . . ., 84, 88,91, 94, 97

)

Off

, Off --- ---

50, 53, 56, 59, 63, 66, . . ., 75, . . ., 84, 88, 91, 94, 97

50, 53, 56, 59, 63, 66, 69, . . ., 84, 88, 91, 94, 97

50, 53, 56, 59, 63,66, . . ., 84, 88, 91, 94, 97

Off

POR

Value

--- --- I, X.

--- --- M.

--- --- I.

--- --- M.

Shipped

Value

Notes

SHARED PARAMETERS FOR TACHYARRHYTHMIA THERAPIES

Shared by all Automatic ATP Therapies I.

V. Pulse Width (ms) 0.03, 0.06,

V. Amplitude (V) 1, 2, . . ., 6,

V. Pace Blank (ms) 150, 160, . . .,

ATP Minimum Interval (ms) 150, 160, . . .,

Shared by all VF, VT, and FVT Therapies

Progressive Episode Therapies Enable

0.1, 0.2, . . .,

On,

Off

1.6

240

, . . ., 440 240 240

200

, . . ., 400 200 200

1.6 1.6

Off Off

GEM®III VR System Reference Guide

1-15

Quick Reference

Bradycardia Pacing Parameters

Table 1-11. Bradycardia Pacing Parameters (Sheet 1 of 2)

Parameter Programmable Values

Pacing Mode VVIR,

Lower Rate (ppm, min-1) 34, 35, 40, . . ., 60,

Upper Sensor Rate (ppm, min-1)

Sensitivity (mV) 0.15,

Pulse Width (ms) 0.03, 0.06,

Pulse Amplitude (V) 1, 2, 3, . . ., 6, 8 8 3

Pace Blanking (ms) 150, 160, . . .,

(and

Medtronic Nominal

VVI

70, 75, . . ., 105, 109, 115, 120

80, 85, . . ., 105, 109, 115, 146, 150

0.9, 1.2

0.1, 0.2, . . .,

0.5, 0.6, . . . , 1.6

210, 220, . . ., 440

0.3

, 0.45, 0.6,

120

, 125, 130, 136, 140,

0.4

200

)

POR

Value

VVI VVI

65 40 H.

120 120 H.

0.3 0.3 D, E.

1.6 0.4

320 200

Shipped

Value

Notes

Post-Shock Pacing Parameters

Pulse Width (ms) 0.03, 0.06,

Pulse Amplitude (V) 1, 2, 3, 4, 5,

Pace Blanking (ms) 150, 160, . . .,

Rate Response Pacing Parameters

Rate Response 1, 2, . . .,

Activity Threshold Low, Medium Low,

Activity Acceleration (sec.) 15, 30, 60 30 30

Activity Deceleration (min.) Exercise, 2.5, 5, 10 5 5

Hysteresis

Enable-Rate (bpm, min-1)

1-16

GEM®III VR System Reference Guide

0.1, 0.2, . . .,

210, 220, . . ., 440

Medium

Medium High, High

Off

, 34, 40, 50, 60, 70, 80 Off Off N.

1.6

886

200

, 8, 9, 10 7 7

1.6 1.6

320 200

High Medium

Automatic Capacitor Formation Parameters

Table 1-11. Bradycardia Pacing Parameters (Sheet 2 of 2)

Parameter Programmable Values

Ventricular Rate Stabilization Parameters

Enable On,

Interval Increment (ms) 50, 60, . . .,

Minimum Interval (ms)

(and

Medtronic Nominal

Off

150

160, 170, . . ., 400

500

, 550, . . ., 900 500 500

)

POR

Value

Off Off

150 150

Automatic Capacitor Formation Parameters

Table 1-12. Automatic Capacitor Formation Parameters

Parameter Programmable Values

Automatic Capacitor Formation Interval (months)

(and

Medtronic Nominal

Off, 1, 2, . . .,

)

POR

Value

6 Off O.

Shipped

Quick Reference

Shipped

Value

Notes

GEM®III VR System Reference Guide

1-17

Quick Reference

Data Collection Parameters

Table 1-13. Data Collection Setup

Parameter Programmable Values

EGM Source Parameters

EGM Channel 1 Source

EGM Channel 1 Range (mV) ± 4, ± 8, ± 16 ± 8 ± 8

EGM Channel 2 Source HVA to HVB, HVA to Vring,

EGM Channel 2 Range (mV) ± 4, ± 8, ± 16 ± 8 ± 8

Store EGM Channel 1? Yes,

Store EGM Channel 2 Yes (ﬁxed) Yes Yes

Store EGM during charging?

Store EGM before tachycardia starts?

(and

Medtronic Nominal

HVA to HVB

Vtip to HVB, Vtip to Vring

Vtip to HVB,

Yes

, No Yes Yes

Ye s ,

, HVA to Vring,

Vtip

)

Vring

POR

Value

HVA to HVB HVA to HVB Q.

Vtip to Vring Vtip to Vring Q.

No No

Shipped

Value

Notes

Device Date/Time

Premature Event Recording Parameters

Premature Event Threshold (%)

Holter Telemetry Parameters

Duration (hours)

(enter time and date) --- --- T.

56, 59, 62, 66, 69, . . ., 84, 88, 91, 94, 97

Off

, 0.5, 1, 2, 4,

8, 16, 24, 36, 46

69 69

Off Off

1-18

GEM®III VR System Reference Guide

Quick Reference

Patient Alert™ Monitoring System Parameters

Table 1-14. Patient Alert™ Setup

Parameter Programmable Values

ALERT TIME

Hour 0, 1, 2, . . ., 23 --- ---

Minute 0, 10, . . ., 50 --- ---

LEAD IMPEDANCE OUT OF RANGE ALERT

Pacing Lead Impedance Alert W.

Enable On, Off Off Off

Minimum Threshold (ohms) 200 Ω (ﬁxed) --- ---

Maximum Threshold (ohms) 2000 Ω (ﬁxed) --- ---

Deﬁbrillation Lead Impedance Alert W.

Enable On, Off Off Off

Minimum Threshold (ohms) 10 Ω (ﬁxed) --- ---

Maximum Threshold (ohms) 200 Ω (ﬁxed) --- ---

Alert Urgency

(and

Medtronic Nominal

Low

, High --- ---

)

POR

Value

Shipped

Value

Notes

LOW BATTERY VOLTAGE ALERT

Alert Enable - Urgency Off,

Battery Voltage Threshold (V) 2.55 (ERI) --- ---

EXCESSIVE CHARGE TIME ALERT

Alert Enable - Urgency Off,

Charge Time Threshold (seconds) 15, 16, 17, 18, . . ., 25 --- ---

NUMBER OF SHOCKS DELIVERED IN AN EPISODE ALERT

Alert Enable - Urgency Off,

Number of Shocks Threshold 1, 2, 3, 4, 5, 6 --- ---

ALL THERAPIES IN A ZONE EXHAUSTED FOR AN EPISODE ALERT

Alert Enable - Urgency Off,

On-Low

, On-High Off Off

On-Low

, On-High Off Off

On-Low

, On-High Off Off

On-Low

, On-High Off Off

GEM®III VR System Reference Guide

1-19

Quick Reference

Patient Information Parameters

Table 1-15. Description of Patient Information

Information Field Description and Action

Patient Enter the patient name or ID number (up to 30 characters).

ID Enter the patient ID.

Date of Birth Select patient’s date of birth.

ICD Number (Not selectable)

Lead 1 . . . Lead 2 . . . Lead 3 . . .

Implant Enter measured values from implant. Using the displayed submenu, enter new

Notes Enter notes about patient or other information.

History (2 ﬁelds) Select medical history from list box. If necessary, you can indicate that more

EF, on Select the Ejection Fraction from a table of values. Then enter the date in the

Physician Select or add the name of the physician.

Phone Enter the phone of the physician.

Hospital Select or add the hospital information.

Last Update (Not selectable)

Displays serial number for implanted ICD after interrogation.

Enter detailed information for leads 1, 2, and 3:

•

Model

•

Position:

• Serial Number

• Manufacturer

• Implant date

information from the keyboard and make list box selections.

information is located in the Notes ﬁeld.

following ﬁeld.

Displays the date of the last Patient Information update.

pick from list of positions, or enter position

1-20

GEM®III VR System Reference Guide

EP Studies Parameters

Table 1-16. EP Studies Parameters (Sheet 1 of 2)

Parameter Selectable Values (and

INDUCTIONS

T-Shock™ Induction Parameters

#S1 2, 3, . . .,

S1S1 (ms) 350, 360, . . .,

410, 420, . . ., 1760

Delay (ms) 50, 60, . . .,

320, 330, . . ., 600

Energy (J) 0.4,

Pathway

Waveform

Pulse Amplitude 8 V (ﬁxed)

Pulse Width 1.6 ms (ﬁxed)

Enable Enabled,

Resume at Deliver

2, 3, . . ., 16, 18, 20, . . ., 30

AX→B

Monophasic

Enabled

0.6

, . . ., 1.8,

, B→AX

, Disabled

400

310

, Biphasic

Disabled

default value

Quick Reference

EP Studies Parameters

) Notes

50 Hz Burst Induction Parameters V.

Interval (ms) 20 ms (ﬁxed)

Pulse Amplitude (V) 1, 2, . . ., 6,

Pulse Width (ms) 0.03, 0.06,

Resume at Burst

Manual Burst Induction Parameters V.

Interval (ms) 100, 110, . . .,

Pulse Amplitude (V) 1, 2, . . ., 5, 6, 8

Pulse Width (ms) 0.03, 0.06,

Resume at Burst

0.1, 0.2, . . .,

Enabled

0.1, 0.2, . . .,

0.6, 0.7, . . ., 1.6

Enabled

1.6

, Disabled

600

0.5

, Disabled

GEM®III VR System Reference Guide

1-21

Quick Reference

EP Studies Parameters

Table 1-16. EP Studies Parameters (Sheet 2 of 2)

Parameter Selectable Values (and

PES Induction Parameters

#S1 1, 2, . . ., 8,

S1S1 (ms) 100, 110, . . .,

S1S2 (ms) Off, 100, 110, . . .,

S2S3 (ms)

S3S4 (ms)

Pulse Amplitude (V) 1, 2, . . ., 5, 6, 8

Pulse Width (ms) 0.03, 0.06,

Resume at Deliver

MANUAL THERAPY PARAMETERS

In general, each manual therapy uses the same parameter values as the automatic therapy. See “Therapy Parameters” beginning on page 1-14.

9, 10, . . ., 15

600

610, 620, . . ., 1760

410, 420, . . ., 600

Off

, 100, 110, . . ., 600 V.

Off

, 100, 110, . . ., 600 V.

0.1, 0.2, . . .,

0.6, 0.7, . . ., 1.6

Enabled

0.5

, Disabled

400

default value

) Notes

1-22

GEM®III VR System Reference Guide

Quick Reference

Fixed Parameters

Table 1-17. Fixed Parameters

Parameter Value Notes

SENSING

Blanking Periods

After a sensed vent. event 120 ms

After charging ends 300 ms

After HV therapy 520 ms

HIGH VOLTAGE THERAPIES

Maximum charging period 30 seconds

Waveform Biphasic

Tilt 50%

VF Synchronization Periods R.

After post-charge blanking 500 ms

After a sensed event 500 ms

Synchronization Refractory Periods

After V. sense during CV synch. 200 ms

After charge during DF synch. 400 ms P.

Post-Therapy

Escape interval after CV/Deﬁb 1200 ms

Suspension of VT Detection after Deﬁbrillation therapy

EP STUDIES

T-Shock™ S1 pacing outputs 1.6 ms at 8 V V.

HARDWARE PARAMETERS

Ventricular rate limit (protective feature)

Input protection 100 kΩ minimum

17 V. events

171 ppm (min

-1

)S.

GEM®III VR System Reference Guide

1-23

Quick Reference

Notes

Post-shock Pace Blanking is reprogrammed by Emergency VVI pacing, but is not displayed on the Emergency Screen.

The VF Initial NID cannot be programmed to a value greater than 30/40 if VT Detection is enabled.

The measured intervals are truncated to a 10 ms multiple (e.g., 457 ms becomes 450 ms). The device uses this truncated interval value when applying the programmed criteria and calculating interval averages.

With a 40 ms sine2 waveform. When using the Cenelec waveform, the rated sensing threshold value will be 1.5 times the rated sine sensing threshold.

This setting applies to all sensing for both tachyarrhythmia detection and bradycardia pacing operations.

Nominal value is blank until detection is enabled.

EGM width is measured on the intracardiac EGM programmed as Channel 2.

The shortest pacing escape interval must exceed all programmed Detection Intervals by at least 60 ms.

These speciﬁcations apply to both automatic and manual therapies, except as noted.

For automatic therapy 3, 4, 5, or 6, energy must be at least 10 joules.

Delivered energy based on a biphasic pulse into a 75 ohm load.

Applies only to the ﬁrst VF therapy that is programmed On.

Smart Mode is only available for Therapies 1, 2, 3, and 4.

Pacing mode must be VVI, and the hysteresis rate must be less than the pacing rate.

The ICD is shipped with Automatic Capacitor Formation Interval set to Off. However, when VF Detection is set to On for the ﬁrst time, the Automatic Capacitor Formation Interval is automatically set to 6 month.

When Reconﬁrm VF is active, a refractory period equal to 60 ms plus the greatest programmed detection interval follows the post-charge blanking period and all paced events.

Both channels appear on-screen as real-time telemetered signals.

When Reconﬁrm VF is active, the VF synchronization (reconﬁrmation) periods are 60 ms plus the greatest programmed detection interval; and the synchronization escape period is equal to the current lower rate (i.e., sensor or programmed lower rate) escape period.

Does not apply during therapies or programmed high rates.

The time stamp on episode records and other stored data is determined by the device’s date/time clock.

Delivered in the VVI mode.

1-24

GEM®III VR System Reference Guide

Quick Reference

Delivered in the VOO mode.

After a POR, all programmed Patient Alert conditions are disabled. The Reset condition itself activates a high-urgency alert that sounds every

twenty hours

For manual ramp therapy, 6 is the nominal number of pulses, and 97% is the nominal value for % of R-R interval.

until cleared.

Notes

GEM®III VR System Reference Guide

1-25

Quick Reference

Notes

1-26

GEM®III VR System Reference Guide

Emergency Therapy

Overview 2-2

Effect on System Operation 2-3

On-Screen and Display Panel Buttons 2-3

Emergency Deﬁbrillation 2-4

Emergency Cardioversion 2-5

Emergency Fixed Burst Pacing 2-6

Emergency VVI Pacing 2-7

GEM®III VR System Reference Guide

2-1

Emergency Therapy

Overview

The ICD provides the following Emergency therapies:

■

Deﬁbrillation therapy

■

Cardioversion therapy

■

Fixed Burst pacing therapy

■

Maximum output VVI pacing

To deliver an Emergency therapy, the programming head must be positioned over the ICD.

Deﬁbrillation is the default Emergency therapy, and 30 joules is the default delivered energy. When you select

[Emergency] and [DELIVER], the ICD

charges and delivers a biphasic 30 joule shock along the AX>B pathway.

If you select a different deﬁbrillation energy, the programmer resets the energy to 30 joules the next time you select

[Emergency]. Emergency

Cardioversion and Emergency Fixed Burst values remain as selected for the duration of the session.

2-2

Aborting the Therapy – As a safety precaution, the programmer also

displays an

[ABORT] button which immediately terminates any Emergency

therapy in progress.

To return to other programming functions from an Emergency screen, select

[Exit Emergency].

GEM®III VR System Reference Guide

Effect on System Operation

The ICD suspends its 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] re-enables detection.

On-Screen and Display Panel Buttons

The on-screen [Emergency] button and the red mechanical Emergency button by the programmer display panel are equivalent at all times.

Emergency Therapy

Effect on System Operation

Red Emergency Button

The on-screen

[DELIVER] button and the yellow-on-blue mechanical

Functions the same as on-screen

[Emergency]

at all times.

Deliver button by the programmer display panel are equivalent during Emergency operations only. The mechanical Deliver button operates only during Emergency operations.

Yellow-on-Blue

Deliver Button

Functions the same as on-screen

[DELIVER], but only during

Emergency functions.

Temporary Parameter Values

Emergency tachyarrhythmia therapies use the permanently programmed parameters of the ICD. in effect until you begin the temporary operation by selecting After the tachyarrhythmia therapy is complete, the ICD reverts to its permanently programmed values.

test values

that do not change

Test values are not

[DELIVER].

Delivery of Emergency VVI Pacing permanently changes the programmed bradycardia pacing values to those used during emergency pacing (see page 2-7).

GEM®III VR System Reference Guide

2-3

Emergency Therapy

Emergency Deﬁbrillation

To Deliver Emergency 30 Joule Deﬁbrillation

♦

1. Position the programming head over the ICD.

2. Select [Emergency].

3. Select [DELIVER].

If delivery is not conﬁrmed, verify that the programming head is properly positioned and select

To Change the Deﬁbrillation Energy and Deliver

♦

1. From the Emergency Therapy screen, select Energy.

2. Select a new energy value.

3. Select [DELIVER].

[Retry] or [Cancel].

Select to Change

Emergency Deﬁbrillation

Select to Deliver

Emergency Deﬁbrillation

2-4

GEM®III VR System Reference Guide

Energy

Figure 2-1. Emergency Deﬁbrillation Screen

Emergency Cardioversion

To Deliver Emergency Cardioversion

♦

1. Position the programming head over the ICD.

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

Emergency Therapy

Emergency Cardioversion

[Retry] or [Cancel].

Emergency Cardioversion

Select to Change

Energy

Select to Deliver

Emergency Cardioversion

Figure 2-2. Emergency Cardioversion Screen

GEM®III VR System Reference Guide

2-5

Emergency Therapy

Emergency Fixed Burst Pacing

To Deliver Emergency Fixed Burst Pacing

♦

1. Position the programming head over the ICD.

2. Select [Emergency].

3. Select [Fixed Burst].

4. Accept the pacing interval shown on the screen, or select Interval for

a new interval value.

Select to Change

Burst Interval

Press and Hold to Deliver

Emergency Fixed

Burst Pacing

5. Select

If delivery is not conﬁrmed, the programmer displays an error window. Verify that the programming head is properly positioned. Select the window and reselect

[BURST Press and Hold].

[OK] from

[BURST Press and Hold].

Figure 2-3. Emergency Fixed Burst Pacing Screen

2-6

GEM®III VR System Reference Guide

Emergency VVI Pacing

To Deliver Emergency VVI Pacing

♦

1. Position the programming head over the ICD.

2. Select [Emergency].

3. Select [VVI Pacing].

4. Select [PROGRAM]. A successful programming sets the ICD to the

following maximum output bradycardia pacing values.

Pacing Mode VVI

Lower Rate 70 ppm (70 min-1)

Amplitude 8 V

Pulse Width 1.6 ms

Pace Blanking 320 ms

Post Shock Pace Blanking 320 ms

Hysteresis Off

Ventricular Rate Stabilization Off

Emergency Therapy

Emergency VVI Pacing

Reprogrammed by Emergency VVI operation, but not displayed on Emergency screen.

If programming is not conﬁrmed, verify that the programming head is properly positioned and select

[Retry] or [Cancel].

GEM®III VR System Reference Guide

2-7

Emergency Therapy

Emergency VVI Pacing

Parameters (ﬁxed)

Select to Program

Emergency VVI Pacing

Figure 2-4. Emergency VVI Pacing Screen

2-8

GEM®III VR System Reference Guide

Overview

System Description 3-2

Detection and Therapy Overview 3-4

GEM®III VR System Reference Guide

3-1

Overview

System Description

The GEM®III VR Model 7231 Implantable Cardioverter Deﬁbrillator (ICD) System is an implantable medical device system that automatically detects and treats episodes of ventricular ﬁbrillation (VF), ventricular tachycardia (VT), fast ventricular tachycardia (FVT), and bradyarrhythmia. When a cardiac arrhythmia is detected, the implantable device delivers deﬁbrillation, cardioversion, antitachycardia pacing, or bradycardia pacing therapy.

The VF Detection circuitry monitors the cardiac cycle length to identify a VF episode. Upon detection of VF, the ICD provides a biphasic deﬁbrillation shock of up to 30 joules delivered energy. If the VF episode persists, up to ﬁve more individually programmed deﬁbrillation shocks can be delivered.

The VT Detection circuitry monitors the cardiac cycle length to identify the presence of a tachycardia. Upon detection of VT, the ICD delivers its ﬁrst programmed VT therapy to restore the patient’s normal cardiac rhythm. If the VT episode persists, up to ﬁve more individually programmed VT therapies can be delivered. Therapy selections include three methods of antitachycardia pacing and synchronized cardioversion.

3-2

FVT detection can be programmed through the VT Detection algorithm or through the VF Detection algorithm. As with VF and VT, up to six FVT therapies can be independently programmed. Therapy selections include three methods of antitachycardia pacing and synchronized cardioversion.

The ICD provides rate responsive single chamber bradycardia pacing to optimize hemodynamics. An internal piezoelectric sensor enables the ICD to increase and decrease its pacing rate in response to the patient’s detected physical activity.

The ICD is intended for implantation with transvenous or epicardial deﬁbrillation leads. The lead system should consist of bipolar or paired unipolar pacing/sensing leads in the ventricle, and one or two high voltage cardioversion/ deﬁbrillation electrodes. (The Active Can serves as one high voltage electrode.) Sensing of cardiac activity and the delivery of pacing stimuli occur between the ventricular pacing/sensing electrodes.

The physician can use the ICD to conduct noninvasive electrophysiologic studies. The physician can also manually deliver any of the ICD therapies to manage an induced or spontaneous tachyarrhythmia.

GEM®III VR System Reference Guide

device case also

Overview

System Description

A programmable Patient Alert™ monitoring feature notiﬁes the patient by audible tones if certain conditions (low battery voltage, high lead impedance, etc.), selected by the physician, occur. The patient can then respond based on instructions provided by the physician.

The ICD provides the physician with real-time information about its detection and therapy parameters and status. The ICD also provides accumulated data on its operation, including stored electrograms, records of tachyarrhythmia episodes detected and treated, bradycardia interventions, and the efﬁcacy of therapy. All of this information can be printed and retained in the patient’s ﬁle, saved in the programmer to read back at a later time, or saved in electronic format on a ﬂoppy diskette.

GEM®III VR System Reference Guide

3-3

Overview

Detection and Therapy Overview

Implanted sensing electrodes provide a ventricular intracardiac electrogram to the ICD. The ICD measures the time between events to determine V-V intervals, and calculates the ventricular rate from these intervals.

When a V-V interval falls within the programmed VF, VT, or FVT detection zone, it increments a VF or VT event counter. If either counter reaches the Number of Intervals to Detect (NID) programmed by the physician, the ICD detects the arrhythmia and delivers the programmed therapy.

Monitor for next

R-wave

Normal sinus rhythm

Detect depolarization and

Measure the R-R interval

Classify the interval and update

event counters

Detect an arrhythmia episode

Ye s

Deliver therapy

Monitor for redetection and

termination

Redetection

After a therapy delivery, if the VF or VT event counter reaches the programmed “Number of Intervals to Redetect” (RNID), the episode is redetected and the next programmed therapy is delivered. This progression continues until the ICD conﬁrms termination of the episode (page 4-27) or delivers all the therapies programmed for the detected tachyarrhythmia.

3-4

GEM®III VR System Reference Guide

Overview

Detection and Therapy Overview

Therapy

The ICD provides ﬁve ventricular therapies: Burst pacing; Ramp pacing; Ramp+ pacing; synchronized cardioversion; and deﬁbrillation. Each VF episode can be treated with up to six deﬁbrillation shocks. Each VT or FVT episode can be treated with up to six therapies of antitachycardia pacing and/or cardioversion. An FVT therapy set must end with at least one cardioversion therapy.

Suspending Detection and Therapy

Automatic Suspension of Detection

Detection is temporarily suspended during:

■

Programming head application (unless [Resume] is programmed) or other magnet application. Detection resumes automatically when the head or magnet is removed.

■

Temporary programmer operations such as manual and emergency therapies delivered through the programmer. Detection remains suspended until the programming head is removed or programmed.

[Resume] is

Note: If the Resume at Deliver feature is disabled

and

detection was suspended before a temporary induction is performed, then detection remains suspended.

■

Automatic daily lead impedance and battery voltage measurements (see page 10-33). Detection resumes when the measurement is complete.

■

Automatic tachyarrhythmia therapy deliveries, including charging periods for high voltage therapy and automatic capacitor formations. Detection resumes automatically when the therapy or charging period is complete.

VT Detection is temporarily suspended during the ﬁrst 17 ventricular events (paced and sensed) after an automatic ventricular deﬁbrillation therapy.

GEM®III VR System Reference Guide

3-5

Overview

Detection and Therapy Overview

Manually Suspending Detection and Therapy

ICD detection and therapy capabilities can be temporarily suspended by:

■

positioning the programming head, the Patient Alert™ patient magnet, or another magnet over the ICD.

■

executing a [Suspend] command from the programmer.

The bradycardia pacing and manually-initiated therapy capabilities of the ICD are still functional. Suspending detection does not change the

programmed settings of the ICD.

Removing the programming head or magnet from its position over the ICD restores the ICD to normal operation. If automatic detection is enabled, the

[Resume] button causes the ICD to resume automatic detection even

while the programming head is in position over the ICD.

Disabling Detection and Therapies

Automatically Disabling Detection and Therapies

The ICD turns off VT Detection if a power-on reset (POR) occurs. The programmable parameter tables starting on page 1-13 list the POR values for all programmable parameters.

3-6

The ICD automatically turns off all VT and VF automatic therapies if three consecutive 30-second charges have failed to reach the programmed energy level (see “Charge Circuit Inactive” on page 5-4).

Manually Disabling Detection and Therapies

To turn off the automatic detection and therapy functions of the ICD, program the functions

1. Select the Params icon and choose the Detection option.

2. Set the Enable parameters to Off.

3. Position the programming head and select [PROGRAM].

To re-enable automatic detection and therapy, reprogramming is required.

GEM®III VR System Reference Guide

Off via the programmer.

Tachyarrhythmia Detection

Sensing 4-2

VF Detection 4-5

VT Detection 4-8

Combined Count Detection 4-11

VT Stability Option 4-13

EGM Width Criterion 4-15

FVT Detection 4-21

Termination and Redetection 4-26

GEM®III VR System Reference Guide

4-1

Tachyarrhythmia Detection

Sensing

Proper sensing is essential for the safe and effective use of the ICD.

To provide appropriate sensing, the ICD uses auto-adjusting sensing thresholds after paced and sensed events (see page 4-3).

Programming for Appropriate Sensing

The programmable sensitivity threshold deﬁnes the minimum electrical amplitude that the ICD recognizes as a ventricular event.

A combination of high pacing pulse width and/or amplitude with a low sensitivity threshold may cause inappropriate sensing after pacing. Programming a lower pulse width, lower amplitude, longer pace blanking, or a higher threshold may eliminate this inappropriate sensing.

Ventricular Sensing

A ventricular sensitivity threshold of 0.3 mV is recommended to maximize the probability that VF will be detected.

■

Always verify that the ICD is sensing and detecting VF properly. You may need to reposition or replace the ventricular sensing lead.

■

A value greater than 0.6 mV is not recommended except for testing and troubleshooting, as it may lead to undersensing or underdetection.

■

Carefully evaluate the potential for increased susceptibility to EMI and oversensing before changing the ventricular sensitivity threshold to its most sensitive setting of 0.15 mV.

■

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

■

If the ICD is not sensing or detecting properly, program all automatic therapies to continuously for life-threatening arrhythmias until you program automatic therapies

Off and evaluate the ICD system. Monitor the patient

On again.

4-2

GEM®III VR System Reference Guide

Tachyarrhythmia Detection

Sensing

Auto-Adjusting Sensitivity Thresholds

The ICD automatically adjusts its sensitivity threshold following certain paced and sensed events (Figure 4-1) to reduce the incidence of T-wave sensing. The auto-adjusting thresholds increase dramatically (Table 4-1), and then gradually return to their programmed settings. Note that the thresholds may already differ from their programmed values, having been adjusted by the preceding sensed or paced event.

Table 4-1. Auto-Adjusting Sensitivity Threshold Values

the sensitivity threshold is:

After a sensed event

After a paced event

Up to a maximum of 8x the programmed value.

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

Up to a maximum of 1.8 mV.

Until the preceding 450 ms decay, or the programmed threshold, is restored.

Increased to 75% of EGM peak. 450 ms decay constant

Increased to 4.5x the programmed value. 450 ms decay constant.

Ventricular EGM

Programmed

Sensitivity Threshold

Programmed

Post-Pace Blanking

Figure 4-1. Auto-Adjusting Sensitivity Threshold

4.5x

Changing Threshold

Post-Pace Post-Sense

V P

V S

GEM®III VR System Reference Guide

V P

V S

4-3

Tachyarrhythmia Detection

Sensing

Blanking Periods

During a blanking period the ICD does not sense electrical signals. Blanking periods avoid sensing ICD outputs, post-pacing polarization, T-waves, and multiple sensing of the same event. The blanking periods following paced events are longer than those following sensed events to avoid sensing the depolarization signal on the electrodes.

Table 4-2. Programmable Blanking Periods

Blanking after ventricular bradycardia pace 150 – 440 ms

Pace blanking during high voltage therapy 150 – 440 ms

Blanking after antitachycardia pace 150 – 440 ms

Table 4-3. Non-Programmable Blanking Periods

Blanking after sensed ventricular event 120 ms

Blanking after the end of a cardioversion or deﬁbrillation charging period

Blanking after delivered cardioversion or deﬁbrillation therapy 520 ms

300 ms

Refractory Periods

4-4

Synchronization refractory periods help prevent delivery of pacing or shock pulses during the ventricular vulnerable period. (Refer to “High Voltage Synchronization” on page 5-5 for more detail.)

Note: Refractory periods do not affect tachyarrhythmia detection.

Ventricular refractory period after charging ends during deﬁbrillation or cardioversion synchronization

Ventricular refractory period after ventricular sense during cardioversion synchronization

GEM®III VR System Reference Guide

Table 4-4. Refractory Periods

400 ms

200 ms

VF Detection

Tachyarrhythmia Detection

VF Detection

The ICD detects VF by applying the VF Interval Criterion. If the ICD senses the programmed number of VF intervals, it detects a VF episode and delivers a VF therapy.

VF Detection details begin on page 4-7.

Table 4-5. VF Detection Programmable Parameters

VF Enable On or Off

Sensitivity (mV)

VF Interval (Rate) V-V intervals shorter than the programmed interval

VF Initial NID Number of Intervals to Detect:

VF Redetect NID Number of Intervals to Redetect:

The programmed sensitivity value applies to ventricular tachyarrhythmia detection and bradycardia pacing.

Minimum level of electrical signal that registers as a sensed ventricular event.

are counted as VF events. (Rates are shown in parentheses.)

number of VF events the ICD must count to detect a VF episode.

number of VF events the ICD must count to redetect VF after a therapy.

Programming VF Detection

To ensure proper VF detection, you should not program the VF Interval below 300 ms.

Programming the ventricular sensitivity to 0.3 mV is recommended. A value greater than 0.6 mV is not recommended except for testing and troubleshooting. Also, carefully evaluate the possibility of increased susceptibility to EMI and oversensing before changing the sensitivity to its minimum (most sensitive) setting of 0.15 mV.

You can accelerate redetection by programming the Redetect NID lower than the Initial NID.

When VF Detection is enabled for the ﬁrst time (i.e., at implant) the ICD automatically changes the Automatic Capacitor Formation Interval from

Off to 6 month.

GEM®III VR System Reference Guide

4-5

Tachyarrhythmia Detection

VF Detection

♦

VF Detection cannot be programmed Off unless VT Detection is also programmed

Off.

To Program VF Detection

1. Select the Params icon and choose the Detection option. The

programmer displays the Detection screen (shown below).

2. Tu r n

3. Position the programming head and select [PROGRAM].

VF Enable to On and select VF Detection parameters.

Figure 4-2. Detection Screen Example

4-6

GEM®III VR System Reference Guide

Tachyarrhythmia Detection

VF Detection

How VF Detection Works

VF Interval Criterion

When a V-V interval is shorter than the programmed VF Interval, the ICD marks that event as a VF event and tallies it in memory. If the number of VF events reaches the programmed episode and delivers the ﬁrst programmed VF therapy. Following the therapy, if the number of VF events reaches the redetects VF and delivers the next programmed VF therapy. (See also “Combined Count Detection” on page 4-11.) VF NIDs are deﬁned as a number of VF events within the last sixteen intervals). All NID values are 75% of the detection window: 12/16, 18/24, etc.

VF Intervals (< 320 ms)

VF Initial NID, the ICD detects a VF

VF Redetect NID, the ICD

VF detection window

(e.g., twelve of the

A VF episode is declared when the VF counter reaches 12 (of the last 16 events).

V S

VF On 12/16 9/12 320 ms

VT On 12 8 400 ms

Sensitivity: 0.3 (mV)

V S

Enable Initial Redetect Interval

V S

VF Event Counter:

FSFSFSFSFSFSFSFSFSFSF

123456789101112

Figure 4-3. VF Detection Example

GEM®III VR System Reference Guide

F S

200 ms

4-7

Tachyarrhythmia Detection

VT Detection

The ICD detects VT by applying the VT Interval Criterion. If the ICD senses the programmed number of VT intervals, it detects a VT episode and delivers a VT therapy.

VT Detection details begin on page 4-10.

Table 4-6. VT Detection Programmable Parameters

VT Enable On or Off

Sensitivity (mV)

VT Interval (Rate) V-V intervals shorter than the programmed interval

VT Initial NID Number of Intervals to Detect:

VT Redetect NID Number of Intervals to Redetect:

The programmed Ventricular Sensitivity value applies to ventricular tachyarrhythmia detection and bradycardia pacing.

Minimum level of electrical signal that registers as a sensed event.

are counted as VT events. (Rates are shown in parentheses.)

number of VT events the ICD must count to detect a VT episode.

number of VT events the ICD must count to redetect VT after a therapy.

4-8

Programming VT Detection

To ensure proper VT detection, program the VT Interval to a value that is at least 40 ms longer than the patient‘s tachycardia interval, and at least 40 ms longer than the programmed

Programming the ventricular sensitivity to 0.3 mV is recommended. (See “Programming for Appropriate Sensing” on page 4-2).

You can accelerate redetection by programming the Redetect NID lower than the Initial NID.

To ensure VF Detection backup during VT episodes, VT Detection cannot be

On unless VF Detection is also On.

GEM®III VR System Reference Guide

VF Interval.

Tachyarrhythmia Detection

To Program VT Detection

♦

1. Select the Params icon and choose the Detection option. The programmer displays the Detection screen (shown below).

VT Detection

2. Tu r n

3. Position the programming head and select [PROGRAM].

VT Enable to On and select VT Detection parameters.

Figure 4-4. Detection Screen Example

GEM®III VR System Reference Guide

4-9

Tachyarrhythmia Detection

VT Detection

How VT Detection Works

VT Interval Criterion

When the V-V interval is shorter than the programmed VT Interval, the ICD marks that event as a VT event and tallies it in memory. (See also “VT Stability Option” on page 4-13). If the number of VT events reaches the programmed ﬁrst programmed VT therapy (See also “EGM Width Criterion” on page 4-15).

VT Initial NID, the ICD detects a VT episode and delivers the

After the therapy, if the number of VT events reaches the the ICD redetects VT and delivers the next programmed VT therapy. (See also “Combined Count Detection” on page 4-11.) The ICD counts consecutive VT events. The event counter resets to zero whenever an interval fails to satisfy the Interval criterion, or the VT Stability option, if it is

On. The VT counter remains at its current value if an interval is shorter

than the programmed

VT intervals > 320 and < 400 ms

V S

VF On 12/16 9/12 320 ms

VT On 12 8 400 ms

Sensitivity (mV): 0.3

V S

Enable Initial Redetect Interval

V S

VT Counter Value:

VSV

TSTSTSTSTSTSTSTSTST

123456789101112

VT Redetect NID,

VF Interval.

A VT episode is declared when the VT counter reaches 12.

200 ms

A VT event increases the VT counter by one.

A normal sensed beat (≥ 400 ms) clears the counter to zero.

A VF event suspends, but doesn’t clear, the VT count.

4-10

Figure 4-5. VT Detection Example

GEM®III VR System Reference Guide

Combined Count Detection

Combined Count detection helps the ICD promptly detect or redetect a ventricular tachyarrhythmia when the interval is ﬂuctuating between the VF and VT zones. The ICD tracks the combined number of events registered on the VF and VT counters, and if this sum reaches the Combined Number of Intervals to Detect (CNID), VF or VT is detected. Combined Count Detection also applies to redetected episodes.

Combined Count detection is automatic (not programmable) when VT Detection is enabled, and cannot be disabled.

How Combined Count Detection Works

Combined Count Detection automatically applies a Combined Number of Intervals to Detect (CNID) when the VF event counter reaches six. The ICD calculates the CNID as follows:

Initial CNID = VF Initial NID x 7/6 (rounded down) Redetect CNID = VF Redetect NID x 7/6 (rounded down)

Tachyarrhythmia Detection

Combined Count Detection

For example, if the VF Initial NID is programmed to 18, the Initial CNID is

21. If the VF Redetect NID is 12, the Redetect CNID is 14.

Combined Count detection is fulﬁlled when the sum of the VF and VT event counters equals or exceeds the CNID. The ICD then reviews the eight intervals preceding detection:

■

any

of the eight was in the VF zone, the episode is classiﬁed as VF.

■

all

eight were outside the VF zone, the episode is classiﬁed as VT.

GEM®III VR System Reference Guide

4-11

Tachyarrhythmia Detection

Combined Count Detection

Surface ECG

Marker Channel™

VF Event Count VT Event Count

Without Combined Count Detection, the arrhythmia would be detected after 18 beats

VF = 12

Counter

VT Counter VT Counter

Figure 4-6. Combined Count Detection Example

FSF

12 3 45

FSF

VF NID = 12/16, VT NID = 12, CNID = 14

With Combined Count Detection, the arrhythmia is detected after 14 beats

VT = 12

15105

Counter

T S

VF = 12

T S

FSFSF

FSF

Combined Count (VT+VF) = 14

VF = 6

VT = 12

15105

4-12

GEM®III VR System Reference Guide

VT Stability Option

VT Stability is an optional detection criterion that allows the ICD to withhold VT detection for rapid rhythms (in the VT detection zone) with irregular intervals.

VT Stability (ms) Off, or the maximum acceptable variation among

Programming VT Stability Option

Choosing a small VT Stability value (such as 30 ms) may not allow for the normal VT interval variation. Thus, smaller VT Stability values may decrease the sensitivity of the ICD to detect VT.

The VT Stability option compares measured intervals that have been shortened to multiples of 10 ms, permitting a rounding error of up to +10 ms from the programmed VT Stability value.

To Program VT Stability

♦

1. Select the Params icon and choose the Detection option. The

Tachyarrhythmia Detection

VT Stability Option

Table 4-7. VT Stability Option Programmable Parameter

measured intervals

programmer displays the Detection screen.

2. Select a value for

3. Position the programming head and select [PROGRAM].

VT Stability.

GEM®III VR System Reference Guide

4-13

Tachyarrhythmia Detection

VT Stability Option

How the VT Stability Option Works

When the VT Stability option is On, an interval in the VT zone is considered previous intervals is greater than the programmed VT Stability interval.

The ICD does not apply the VT Stability option until the VT event count reaches three. When an interval in the VT zone fails to meet the VT Stability option, it is marked as a normal sensed event and the VT event count resets to zero.

The VT Stability option must be re-satisﬁed during redetection if it is enabled.

unstable

if the difference between it and any of the three

VT Stability is not applied until VT count reaches three.

V S

4 8 0

VT Counter Value:

Unstable event: Varies from previous interval

by 70 ms. Event is marked as a normal sensed

beat and VT counter resets to zero.

Enable Initial Redetect Interval

VF On 12/16 9/12 320 ms

VT On 12 8 540 ms

Ventricular Sensitivity (mV): 0.3 VT Stability (ms): 50

Stable events: Each differs from the three before it by

50 ms or less, and they are marked as VT events.

T S

2 30123 2345

T S

4 8 0

TST

V S

4 7 0

TST

200 ms

Unstable event: Varies from previous interval

by 60 ms. VT counter resets to zero.

4-14

Figure 4-7. VT Stability Option

GEM®III VR System Reference Guide

EGM Width Criterion

The optional EGM Width Criterion can improve the speciﬁcity of VT detection by identifying inappropriately detected supraventricular arrhythmias (such as sinus tachycardia and atrial ﬁbrillation or ﬂutter). The ICD measures the QRS complexes during a high rate episode, and detects the episode as VT only if a sufﬁcient number of the QRS complexes are wide.

For more detail on the EGM width criterion, see page 4-18.

EGM Width

Width Threshold (ms)

Slew Threshold (mV/s)

Note: The ICD provides three diagnostic tools to evaluate and verify the

EGM Width parameter settings:

– The EGM Width test (page 8-9) helps you ﬁnd the most effective

– QRS Snapshots (page 10-25) show how the parameters

– The Passive criterion setting (page 4-16) provides ambulatory

Tachyarrhythmia Detection

EGM Width Criterion

Table 4-8. EGM Width Criterion Parameters

On, Off, or Passive

A sensed event is designated wide if its QRS complex equals or exceeds this width.

Deﬁnes the beginning and end of each sensed QRS complex, using the rate of amplitude change in the EGM 2 waveform.

parameter settings by measuring the patient’s QRS complexes during sinus rhythm.

settings are being applied during automatic detection.

monitoring of the ICD’s ability to discriminate between VT and SVTs.

GEM®III VR System Reference Guide

4-15

Tachyarrhythmia Detection

EGM Width Criterion

Programming the EGM Width Criterion

Cautions: The EGM Width criterion should not be used for patients with fast or poorly tolerated VTs.

The EGM Width criterion is less likely to be effective in patients with narrow complex VTs, with bundle branch block, or whose QRS complexes are affected by antiarrhythmic medications.

When the EGM Width Criterion is programmed to measures and stores QRS widths during VT episodes, but the criterion is not applied for VT detection.

Select the slew threshold independently of the width threshold to establish proper QRS width measurements during sinus rhythm. Recommended initial threshold settings are:

– the lowest slew threshold that provides predictable, consistent

width measurements (variation of 12 ms or less) during sinus rhythm.

– the lowest width threshold that exceeds all the width

measurements taken during sinus rhythm.

Higher slew thresholds tend to result in narrower and possibly more consistent QRS width measurements. Lower slew thresholds tend to provide wider and possibly more variable QRS width measurements (see the drawing on page 4-20).

A larger width threshold increases the speciﬁcity of VT detection, but may also decrease the sensitivity. While evaluating patients with a concomitant pacemaker, measure the intrinsic QRS widths during normal sinus rhythm.

Passive, the ICD

4-16

The width threshold and slew threshold parameters can also be programmed from the EGM Width Test screen (when the criterion is set to

On or Passive).

GEM®III VR System Reference Guide

Tachyarrhythmia Detection

To Program the EGM Width Criterion

♦

1. Select the Params icon and choose the Detection option. The programmer displays the Detection screen.

EGM Width Criterion

Parameters

2. Set

3. Position the programming head and select [PROGRAM].

EGM Width to On or Passive and select values for the Width

Threshold and Slew Threshold.

Figure 4-8. EGM Width Criterion Parameters

GEM®III VR System Reference Guide

4-17

Tachyarrhythmia Detection

EGM Width Criterion

How the EGM Width Criterion Works

The EGM Width Criterion is based on the premise that QRS complexes of ventricular origin are generally wider than those of supraventricular origin. When a fast ventricular rhythm fulﬁlls the other programmed VT detection criteria and the EGM Width Criterion is programmed the eight preceding QRS complexes, as sensed on the programmed

EGM 2 electrode source (see Figure 4-10). If fewer than six of these eight

complexes in the “lookback window” are wide, the ICD does not identify the episode as VT.

The EGM Width Criterion is only applied on initial detection of a VT episode. It does not apply to VF detection, FVT detection, or redetection of VT after therapy.

Measuring a QRS Complex

The ICD identiﬁes the start and end points of a sensed QRS complex using the slew threshold parameter. Slew rate is the millivolts per second) of the sensed EGM amplitude.

On, the ICD reviews

rate of change

(in

4-18

Low rate of

amplitude change

High rate of

amplitude change

Higher slew thresholds give narrower QRS widths. Lower slew thresholds give wider QRS widths. Select the lowest slew threshold that provides predictable, stable QRS width measurements of the patient’s normal sinus rhythm.

Figure 4-9. Effect of Slew Threshold on QRS Width (Example)

The ICD measures the slew rate every 4 milliseconds, and marks the start of the QRS at the earliest point where the slew rate ﬁrst reaches the programmed threshold (Figure 4-9). The end of the QRS occurs at the last point where slew rate exceeds the programmed slew threshold. The QRS width is then calculated as the time in milliseconds between the start and end of the QRS.

GEM®III VR System Reference Guide

48 mV/s slew threshold results in 104 ms QRS width 90 mV/s slew threshold results in 84 ms QRS width

104 ms QRS width

48 mV/s slew threshold

90 mV/s slew threshold

84 ms QRS width

Bipolar EGM

Tachyarrhythmia Detection

EGM Width Criterion

Classifying the QRS Complex

If the width of the QRS is less than the programmed width threshold, it is designated as or if it is less than 16 milliseconds (i.e., too narrow to represent a normal sinus rhythm), it is designated as

Far Field EGM

Narrow. If the width equals or exceeds the width threshold,

Wide.

QRS measurements are made from the programmed EGM source for EGM channel 2

V S

VT Counter Value:

QRS Width in ms:

V S

80 68 96 100 88 96 104 88

EGM Width: ON

Width Threshold (ms): 88

Slew Threshold (mV/s): 30

VF FVT VT

Detection Status: ON OFF ON

Interval (ms): 320 500

Initial NID: 18/24 12

Figure 4-10. Example of EGM Width Criterion Met

Classifying the Episode

When a ventricular high rate fulﬁlls the Initial (or Combined) NID, the ICD “looks back” at the eight complexes preceding, but not including, the event that fulﬁlled detection.

■

If six or more of these eight QRSs are wide, the EGM Width criterion is satisﬁed and the ICD detects the episode as VT (Figure 4-10).

■

If three or more are narrow, the criterion is not satisﬁed and the VT counter resets to zero. (Figure 4-11: the criterion is not met because the slew threshold is set too high.)

(8 events not including NID event)

When the VT NID is reached, the device reviews the recent QRS measurements.

Six of the eight events were measured “wide” (≥ 88 ms), and the episode is detected as VT.

200 ms

GEM®III VR System Reference Guide

4-19

Tachyarrhythmia Detection

EGM Width Criterion

VT beats are measured narrower than the width threshold.

Far Field EGM

Bipolar EGM

V S

VT Counter Value:

QRS Width in ms:

EGM Width: ON

Width Threshold (ms): 88

Slew Threshold (mV/s): 48

Detection Status: ON OFF ON

Interval (ms): 320 500

Initial NID: 18/24 12

V S

76 76 84 92 84 80 88 84

VF FVT VT

T S

With the slew threshold set to 48 mV/s, several

TST

(8 events not including NID event)

V S

11 (12)0

200 ms

When the episode fails to meet the

EGM Width criterion, the VT counter

Slew = 48 mV/s

84 ms width

resets to zero.

4-20

Figure 4-11. Effect of Slew Threshold on Rhythm Classiﬁcation

GEM®III VR System Reference Guide

FVT Detection

Tachyarrhythmia Detection

FVT Detection

The ICD can be programmed to further classify a tachycardia as Fast Ventricular Tachycardia (FVT). The ICD provides an FVT episode counter and a separate therapy regimen for FVT episodes.

FVT Detection details begin on page 4-23.

Table 4-9. FVT Detection Programmable Parameters

FVT Enable via VF, via VT, or Off

Ventricular Sensitivity

(mV)

FVT Interval (Rate) V-V intervals between this value and the

The programmed sensitivity value applies to tachyarrhythmia detection and bradycardia pacing.

Minimum level of electrical signal that registers as a sensed ventricular event.

programmed VF Interval are marked as FVT events. (Rates are shown in parentheses.)

Programming FVT Detection

To ensure VF Detection backup, FVT Detection cannot be On unless VF Detection is also

On.

For FVT Detection zone. For FVT Detection

via VF, the FVT Interval is programmed within the VF

via VT, the FVT Interval is within the VT zone. This

choice should depend on the patient’s VF and VT cycle lengths. After determining a reliably sensitive VF Interval, consider the following:

■

If the patient exhibits a clinical VT cycle length in the VF zone, select

via VF to ensure reliable detection of VF. (VT Detection need not be

enabled at all.)

■

If the patient exhibits two clinical VTs, both outside the VF zone, select

via VT to prevent misclassiﬁcation of VF, and to offer a separate

therapy regimen for each VT.

■

If the patient has only one clinical VT, outside the VF zone, select VF and VT Detection only, with

FVT Enable set to Off.

Select the VF, VT, and FVT Intervals at least 40 ms apart to allow for normal variations in the patient’s interval.

FVT Detection uses the VF event counter and the programmed VF NID if set to

via VF, or the VT counter and VT NID if set to via VT.

GEM®III VR System Reference Guide

4-21

Tachyarrhythmia Detection

FVT Detection

♦

To Program FVT Detection

1. Select the Params icon and choose the Detection option. The

programmer displays the Detection screen.

2. Set

3. Position the programming head and select [PROGRAM].

FVT Enable to via VT or via VF. Select the FVT Interval and

Ventricular Sensitivity values.

Figure 4-12. Programming FVT Detection

4-22

GEM®III VR System Reference Guide

Tachyarrhythmia Detection

FVT Detection

How FVT Detection Works

FVT Detection Via VF

When you set FVT Detection to via VF, the ICD detects FVT episodes using the VF event counter.

A V-V interval within the FVT zone is marked as an “FVT via VF” event and tallied on the more sensitive VF event counter. When the VF NID is reached, the ICD reviews the last eight intervals.

■

any

of the last eight intervals is in the VF zone, it detects the

episode as VF.

■

all

of the last eight intervals are outside the VF zone, it detects the

episode as FVT (Figure 4-13).

FVT Detection Via VT

When you set FVT Detection to via VT, the ICD detects FVT episodes using the VT event counter.

A V-V interval within the FVT zone is marked as an “FVT via VT” event and tallied on the more speciﬁc, consecutive VT event counter. The VT Stability option must also be satisﬁed if it is enabled. When the VT NID is reached, the ICD reviews the last eight intervals.

■

any

of the last eight intervals is in the VF or FVT zones, it detects

the episode as FVT.

■

all

of the last eight intervals are outside the FVT and VF zones, it

detects the episode as VT.

GEM®III VR System Reference Guide

4-23

Tachyarrhythmia Detection

FVT Detection

VF NID reached. Since none of the last eight intervals is a VF interval, the ICD classiﬁes the episode as FVT and

Combined Count Detection of FVT

Combined Count Detection (page 4-11) also applies to the FVT zone. If the VF event counter reaches six, and the sum of the VF and VT event counters equals or exceeds the CNID, the ICD “looks back” at the eight intervals preceding detection:

■

If any of the eight was in the VF zone, the episode is detected as VF.

■

If none were in the VF zone but one or more was in the FVT zone, the episode is detected as FVT.

■

If all eight were outside the VF and FVT zones, the episode is classiﬁed as VT.

will deliver an FVT therapy.

4-24

V S

Enab

V S

VF Counter:

123 4 567 89101112

LOOKBACK WINDOW

(8 INTERVALS BEFORE NID)

Initial

Redetect

VF On 12/16 9/12 320 ms

FVT via VF 260 ms

VT Off

Figure 4-13. FVT Detection Via VF Example

GEM®III VR System Reference Guide

Inter

200 ms

Blanking

Depolarization

Blanking

Depolarization

VF Detection Zone

120 ms

Tachyarrhythmia Detection

FVT Detection

Zone Merging After Detection

For FVT via VF detection, the FVT zone merges with the VF zone after detection or redetection of VF. For FVT via VT detection, the FVT zone merges with the VT zone after detection or redetection of FVT or VF. In both instances, the merged-zone conﬁguration remains until episode termination. The merged zone uses the event counting and therapies for the faster arrhythmia, to ensure that the ICD delivers sufﬁciently aggressive therapies during an extended or highly variable tachyarrhythmia episode. (See also “Progressive Episode Therapies” on page 5-33.)

Before initial detection: three detection zones

Interval

Lower Rate

Period

Lower Rate

Period

FVT Detection Zone

FVT

Interval

VT Detection Zone

After detection of VF: two zones for redetection

VF Detection Zone VT Detection Zone

Interval

Blanking

Depolarization

Blanking

Depolarization

VF Detection Zone

120 ms

VF Detection Zone

120 ms

Figure 4-14. Zone Merging (FVT Detection Via VF)

Before initial detection: three detection zones

FVT Detection Zone

VF Interval FVT

VT Detection Zone

Interval

After detection of VF or FVT: two zones for redetection

FVT Detection Zone

Interval

Figure 4-15. Zone Merging (FVT Detection Via VT)

GEM®III VR System Reference Guide

Lower Rate

Period

Interval

Lower Rate

Period

Interval

4-25

Tachyarrhythmia Detection

Termination and Redetection

Outcome Monitoring

After delivering an automatic therapy, the ICD monitors the cardiac interval for three possible outcomes:

■

Termination of the episode.

■

Redetection of the original ventricular tachyarrhythmia.

■

Redetection of a different ventricular arrhythmia, including

VT acceleration.

Further automatic ventricular therapies are not delivered unless the patient‘s cardiac rhythm fulﬁlls the redetection requirements for a ventricular tachyarrhythmia.

The EGM Width Criterion is not applied during redetection. However, the VT Stability criterion must be continually re-satisﬁed throughout redetection if it is enabled.

Programming Considerations

You can accelerate redetection by programming Redetect NIDs lower than the Initial NIDs.

Both the VF Redetect NID and the VT Redetect NID take effect during any type of ventricular arrhythmia episode.

If you program the page 5-33), a slower arrhythmia (e.g., VT) may receive therapies for a faster arrhythmia (e.g., VF) during redetection.

Progressive Episode Therapies option On (see

4-26

VT Detection is temporarily suspended for 17 events, paced or sensed, following deﬁbrillation therapy.

GEM®III VR System Reference Guide

Tachyarrhythmia Detection

Termination and Redetection

Therapy Efﬁcacy

A therapy is considered successful if arrhythmia termination occurs prior to any redetection. The therapy is considered unsuccessful if redetection occurs before termination.

If all programmed therapies are unsuccessful, the ICD suspends them until either:

■

the episode terminates, or

■

Detection is manually reset (by programming Detection Enable Off and then On again) during the episode.

Episode Termination

Episode termination occurs when eight consecutive V-V intervals are greater than or equal to the VT detection interval.

Once the ICD detects an arrhythmia, it considers the episode as ongoing until it detects episode termination. Any subsequent detection after termination marks the start of a new episode.

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

third

event on the electrogram.)

A rhythm that does not satisfy the termination deﬁnition is considered part of an ongoing episode, but the ICD does not deliver the next programmed therapy until the redetection criteria are fulﬁlled.

Redetection

The ICD redetects an arrhythmia if the VF or VT event counter reaches its Redetect NID, or if the combined VF and VT event counters reach the Redetect CNID (see “Combined Count Detection” on page 4-11). The ICD then delivers the next programmed therapy for the current arrhythmia, and resumes monitoring for the outcome of that therapy.

VF Interval when VT Detection is programmed Off.

GEM®III VR System Reference Guide

4-27

Tachyarrhythmia Detection

Termination and Redetection

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

Figure 4-16 illustrates redetection of VT after cardioversion therapy.

VT Acceleration

The ICD classiﬁes a VT as accelerated when it redetects during a VT episode and the average of the four intervals before redetection has decreased by 60 ms or more, compared to the average of the four intervals before the initial VT detection. to evaluate future VT accelerations under the 60 ms rule above.

If VT acceleration occurs after the delivery of an antitachycardia pacing sequence, the ICD skips the subsequent sequences of the pacing therapy for the duration of this episode and delivers the next programmed VT therapy.

The current redetection is used

4-28

Or before the most recent “accelerated” VT redetection.

GEM®III VR System Reference Guide

0.6 joule cardioversion shock.

Not sensed in the blanking period after cardioversion.

Tachyarrhythmia Detection

Termination and Redetection

Sensed, measured as 660 ms, and marked as a normal sensed event.

VRV

3 3 0

After eight consecutive intervals within the VT zone, the VT Redetect NID is fulﬁlled and the ICD redetects the VT episode.

Enable Initial Redetect Interval

VF On 12/16 9/12 320 ms

VT On 12 8 400 ms

VT Therapy: 1 2 3 4 5 6

Therapy Status: On On On On On On

Therapy Type: CV CV CV CV CV CV

Energy (J): 0.6 10 30 30 30 30

Figure 4-16. Redetection of VT After Therapy

T S

3 3 0

TSTST

3 3 0

The therapy was unsuccessful: the ICD redetected VT before episode termination (eight consecutive beats outside the detection zones).

3 3 0

200 ms

GEM®III VR System Reference Guide

4-29

Tachyarrhythmia Detection

Termination and Redetection

4-30

GEM®III VR System Reference Guide

Tachyarrhythmia Therapies

High Voltage Therapy Overview 5-2

Deﬁbrillation 5-9

Cardioversion 5-15

Antitachycardia Pacing Therapy Overview 5-20

Programming ATP Therapies 5-22

Burst Pacing 5-24

Ramp Pacing 5-26

Ramp+ Pacing 5-28

Smart Mode 5-30

Progressive Episode Therapies 5-33

GEM®III VR System Reference Guide

5-1

Tachyarrhythmia Therapies

High Voltage Therapy Overview

Deﬁbrillation and cardioversion are the two high voltage therapies provided by the ICD. Up to six deﬁbrillation shocks may be programmed to treat a detected episode of VF. Cardioversion therapy can be programmed as any of the six VT or FVT therapies.

When an arrhythmia is detected and deﬁbrillation or cardioversion is the next programmed therapy, the ICD charges the high voltage capacitors to the programmed energy. When the programmed energy is reached, the ICD initiates a synchronization sequence and attempts to synchronize the pulse to the leading edge of a sensed ventricular event.

Deﬁbrillation and cardioversion therapies can be delivered via the following high voltage electrodes:

■

CAN (HVA) – device can

■

RV (HVB) – RV coil

■

SVC (HVX) – optional supplemental electrode; e.g. SVC coil

Each deﬁbrillation or cardioversion therapy has separately programmable energy and pathway polarity (see “High Voltage Therapy Parameters” on page 5-7). The ICD automatically regulates the pulse width to obtain 50% tilt.

5-2

Comparison of Deﬁbrillation and Cardioversion

A deﬁbrillation shock is delivered for VF; a cardioversion shock is delivered for VT or FVT.

When the ICD delivers a deﬁbrillation therapy, it attempts to synchronize with a sensed R-wave, but does not require such synchronization. However, a cardioversion therapy requires synchronization to a sensed R-wave for delivery to occur.

GEM®III VR System Reference Guide

Tachyarrhythmia Therapies

High Voltage Therapy Overview

Committed vs. Non-Committed Therapies – The ICD can be programmed to reconﬁrm VF before delivering the ﬁrst programmed deﬁbrillation therapy. Reconﬁrmation is attempted only for the initial detection of VF, and only if the Reconﬁrm VF feature is programmed Subsequent VF therapies within the same episode are always

On.

committed

when the capacitors reach their programmed energy, the shock will be delivered. Cardioversion is a

non-committed

therapy: if the ICD cannot

synchronize to a ventricular sensed event, the therapy aborts.

Table 5-1 summarizes the differences between deﬁbrillation and cardioversion.

Table 5-1. Comparison of Deﬁbrillation and Cardioversion

Deﬁbrillation Cardioversion

Episode detected VF VT or FVT

Reconﬁrm arrhythmia First therapy: optional

Later therapies: committed

Synchronization Not required unless

Synchronization successful

Synchronization unsuccessful

Reconﬁrm VF is active

Delivers high voltage pulse Delivers high voltage pulse

Delivers asynchronous deﬁbrillation pulse at end of synchronization sequence (but if Reconﬁrm VF is active, the therapy aborts)

All therapies non-committed (require synchronization)

Required

Abort CV pulse at end of synchronization sequence

GEM®III VR System Reference Guide

5-3

Tachyarrhythmia Therapies

High Voltage Therapy Overview

Charging Period

Warning: If a Charge Circuit Timeout (see below) occurs, please inform a Medtronic representative. Immediate replacement is recommended.

The length of time to charge the ICD high voltage capacitors to the programmed energy (charge time) increases with an increase in programmed energy, battery depletion, or time since the last capacitor formation. Table 1-5 on page 1-8 shows typical charge times to maximum programmed energy at different battery voltages and levels of capacitor formation.

During the capacitor charging period, the ICD:

■

operates in its programmed pacing mode,

■

applies the programmable Post Shock Pacing parameters (see page 6-8), and

■

may lose the telemetry link to the programmer due to electrical noise.

After the charging period completes, the ICD starts a 300 ms blanking period.

Charge Circuit Timeout

If a single charging period reaches 30 seconds, the ICD terminates charging, aborts the therapy attempt (but retains the charge on the capacitors), and resumes detection using the programmed detection criteria. The charge circuit is still active. The ICD records the

Circuit Timeout Device Status Indicator, which is later sent to the

programmer via telemetry. If a

Charge Circuit Timeout indicator is

displayed, please inform a Medtronic representative and replace the ICD immediately.

Charge

5-4

Charge Circuit Inactive

If three consecutive charging periods have each reached 30 seconds, the ICD terminates charging, aborts the therapy attempt, and disables the automatic tachyarrhythmia therapies and manual operations, except for Emergency VVI pacing. The charge circuit is inactive. The ICD records the

Charge Circuit Inactive Device Status Indicator, which is sent to the

programmer via telemetry. If a displayed, do not try to reprogram the ICD. Please inform a Medtronic representative and replace the ICD immediately.

GEM®III VR System Reference Guide

Charge Circuit Inactive indicator is

Tachyarrhythmia Therapies

High Voltage Therapy Overview

High Voltage Synchronization

The synchronization sequence is designed to conﬁrm the continued presence of the arrhythmia and synchronize the high voltage pulse to a sensed R-wave. In general:

■

committed deﬁbrillation therapies are timed to the ﬁrst non-refractory sensed event if possible, or delivered asynchronously if they cannot be synchronized (see page 5-11).

■

non-committed deﬁbrillation therapies (i.e. when Reconﬁrm VF is active) and cardioversion therapies are timed to a non-refractory

arrhythmic

synchronized (see page 5-13 and page 5-17).

The ICD high voltage pulses are synchronized to events sensed on the implanted electrodes. Surface ECGs exhibit morphologies and timing that do not necessarily coincide exactly with those taking place at the electrode sites.

Note: For any delivered high voltage therapy, there is a possibility of inducing an atrial arrythmia.

sensed event if possible, or aborted if they cannot be

GEM®III VR System Reference Guide

5-5

Tachyarrhythmia Therapies

High Voltage Therapy Overview

After A Delivered High Voltage Therapy

Immediately after a delivered high voltage therapy, the ICD starts:

■

a post shock blanking period of 520 ms, and

■

one VVI pacing cycle at 50 ppm (escape interval of 1200 ms).

After the ﬁrst ventricular event, the programmed bradycardia pacing mode resumes, using the Post Shock Pacing parameters (see page 6-8).

The ICD monitors for an outcome from the delivered therapy: either episode termination or redetection. After an automatic deﬁbrillation therapy, VT detection is temporarily suspended for 17 events, or until episode termination is detected, whichever occurs ﬁrst. This feature is designed to reject transient VTs that may follow the high voltage therapy.

After any manual therapy delivered via the programmer (including emergency HV therapies), automatic detection is suspended for as long as the programming head remains over the device, or until

[Resume]

is selected.

After An Aborted High Voltage Therapy

5-6

Following an aborted deﬁbrillation or cardioversion therapy, or an aborted charging period, the ICD reverts immediately to its programmed bradycardia pacing settings.

The ICD resumes monitoring the cardiac cycle for arrhythmias, using the programmed redetection NIDs, after the next paced or sensed ventricular event. If the ICD redetects the same arrhythmia after an aborted therapy, it attempts to synchronize and deliver the same therapy. However, if the ICD detects episode termination, it resumes normal detection.

Note: If a high voltage therapy aborts, leaving the energy stored on the capacitors, the delivered energy of a subsequent cardioversion or deﬁbrillation therapy could be higher than the programmed value.

GEM®III VR System Reference Guide

Tachyarrhythmia Therapies

High Voltage Therapy Overview

High Voltage Therapy Parameters

Energy

The ICD can be programmed to deliver up to 30 joules1, which corresponds to a maximum stored energy of 35 joules. This value is derived from the peak capacitor voltage, which is always greater than the energy delivered by the device. Table 1-6 on page 1-9 compares all of the programmable delivered energy levels to their corresponding stored energy levels. The deﬁbrillation or cardioversion energy level is programmed independently for each therapy.

Waveform

The waveform of the cardioversion or deﬁbrillation pulse is biphasic.

The biphasic pulse consists of two phases. In the ﬁrst phase, current is delivered between the high-voltage electrodes until the pulse decays to 50% of its original voltage. The ICD then truncates the pulse and reverses the current pathway for the second phase by transposing the cathode and anode. After the second phase of the pulse has decayed to 50% of its original voltage, the ICD truncates the pulse.

Second phase

truncated after 50%

pulse decay

Biphasic pulse

inverted after 50%

pulse decay

50% Tilt

Figure 5-1. Biphasic Waveform for Cardioversion and Deﬁbrillation

Tilt

The ICD high voltage pulses are tilt controlled: the output pulse is truncated when it has decayed by a percentage of its initial value, or “tilt.” The ICD uses a ﬁxed tilt value of 50%.

Figure 5-1 shows how the ICD delivers biphasic shocks across a single pathway with 50% tilt. The biphasic pulse is inverted to a negative voltage and then truncated to zero after a 50% decay of its second phase. Negative voltage indicates that the current pathway has been reversed.

Delivered energy of biphasic waveform into 75 ohms.

GEM®III VR System Reference Guide

5-7

Tachyarrhythmia Therapies

High Voltage Therapy Overview

Pathway Polarity

(anode → cathode)

Pathway Polarity

Pathway polarity assigns the implanted electrodes to serve as the anode and cathode in delivering the high voltage pulse. For example, an ICD implanted with two electrodes, CAN ( programmed to deliver current from CAN to RV ( (

B>AX).

Table 5-2. Modes and Polarities for Cardioversion and Deﬁbrillation

Two HV Electrodes:

CAN and RV

Options

CAN → RV = AX>B

RV → CAN = B>AX

HVA) and RV (HVB), can be

AX>B) or from RV to CAN

Three HV Electrodes:

CAN, RV, and SVC

CAN, SVC → RV = AX>B

RV → CAN, SVC = B>AX

5-8

GEM®III VR System Reference Guide

Deﬁbrillation

Tachyarrhythmia Therapies

Deﬁbrillation

Deﬁbrillation shocks are independently programmable for energy and pathway polarity. When Reconﬁrm VF is enabled, the ﬁrst deﬁbrillation therapy delivered during an episode is non-committed.

Table 5-3. Deﬁbrillation Programmable Parameters

VF Therapy Status

Energy (J)

Pathway

Reconﬁrm VF After Initial Charge

Progressive Episode Therapies

Any of the six VF therapies can be programmed Off. The ICD retains the settings but skips the “Off” therapy and immediately delivers the next available therapy.

On or Off.

0.4 – 30 (see page 5-7)

AX>B or B>AX (see page 5-8)

Yes or No (see page 5-13)

On or Off (see page 5-33)

Programming Deﬁbrillation Therapies

No more than one of the six VF Therapies should be programmed to less than 30 joules.

You can program the ICD to reconﬁrm a VF episode before delivering the

ﬁrst

programmed deﬁbrillation therapy only. Subsequent therapies, and

re-applications of an aborted ﬁrst therapy, are always committed.

If the Progressive Episode Therapies feature is enabled, the ICD may deliver a deﬁbrillation therapy at a higher energy level than was programmed. This ensures that each therapy delivered during an ongoing episode is at least as aggressive as the previous therapy (see “Progressive Episode Therapies” on page 5-33).

GEM®III VR System Reference Guide

5-9

Tachyarrhythmia Therapies

Deﬁbrillation

♦

To Program Deﬁbrillation Therapies

1. Select the Params icon, and choose the Therapies menu option.

2. Select [VF] (see Figure 5-2).

3. Enable VF Therapies by setting VF Therapy Status parameters to On.

4. Set Energy and Pathway parameters for each enabled VF Therapy.

5. Enable VF reconﬁrmation by setting Reconﬁrm VF after initial charge

to Yes.

6. Select [PROGRAM].

VF Therapy Screen

Selected

Deﬁbrillation

Parameters

Shared Therapy

Parameters Screen

Selected

Progressive Episode

Therapies Parameter

Figure 5-2. Programmable Deﬁbrillation Parameters

7. To program the Progressive Episode Therapies feature, select

[Shared] (see Figure 5-3).

8. Set Progressive Episode Therapies to On or Off.

9. Select [PROGRAM].

5-10

Figure 5-3. Shared Therapy Parameters Screen

GEM®III VR System Reference Guide

Tachyarrhythmia Therapies

Deﬁbrillation

Committed Deﬁbrillation Synchronization

Note: A deﬁbrillation therapy is

deﬁbrillation shock delivered during an episode

always

committed, unless it is the ﬁrst

and

the Reconﬁrm VF

feature is enabled, (see page 5-13).

A deﬁbrillation therapy is synchronized to a sensed R-wave if possible. Committed deﬁbrillation uses a synchronization escape period of 500 ms to identify the R-wave for delivering the shock.

At the

ﬁrst non-refractory sensed event

, the shock is delivered

(Figure 5-4).

However, if the 500 ms synchronization escape period expires

without a

non-refractory event, the shock is delivered asynchronously (Figure 5-5).

The synchronization interval begins at the end of the 300 ms post-charge blanking period, with an effective refractory period of 100 ms. If the ICD senses a ventricular event during this refractory period, it starts a new synchronization interval. This subsequent synchronization interval begins with a 120 ms blanking period and no additional refractory period.

When Reconﬁrm VF is active, the ﬁrst deﬁbrillation shock is synchronized to a non-refractory

arrhythmic

event (see page 5-13).

At the ﬁrst non-refractory event, the shock is delivered.

After the charge blanking

period, the synchronization

interval of 500 ms begins with

an effective refractory period of

100 ms.

Refractory

Synchronization

Figure 5-4. Deﬁbrillation Synchronized to an Arrhythmic Event

Blanking

C E

300 ms

400 ms

500 ms

C D

520 ms

200 ms

An extended blanking

period of 520 ms begins

after the shock.

GEM®III VR System Reference Guide

5-11

Tachyarrhythmia Therapies

Deﬁbrillation

This refractory sensed

event restarts the

synchronization interval.

Blanking

Refractory

Synchronization

Figure 5-5. Deﬁbrillation Delivered After Failing to Synchronize

These two low-amplitude

events go unsensed.

C E

300 ms 120 ms 520 ms

400 ms

V R

500 ms

C D

The synchronization sequence times out and the device delivers the deﬁbrillation shock.

An extended blanking period of 520 ms begins

200 ms

after the shock.

5-12

GEM®III VR System Reference Guide

Tachyarrhythmia Therapies

Deﬁbrillation

Non-Committed Deﬁbrillation Synchronization

When the Reconﬁrm VF feature is enabled, the ﬁrst deﬁbrillation shock delivered during an episode is synchronized to a non-refractory arrhythmic event, but it aborts if the VF terminates spontaneously into bradycardia or sinus rhythm.

The ICD uses a sequence of reconﬁrmation “windows,” each lasting 60 ms plus the programmed

VT Interval

to identify an ongoing tachyarrhythmia. The ICD deﬁnes a non-refractory sensed ventricular event within this window as

arrhythmic

for reconﬁrmation purposes.

Synchronization begins with a 300 ms post-charge blanking period. After this blanking period the ICD starts a reconﬁrmation window and a refractory period of up to the same duration (

VT Interval

plus 60 ms).

If the next ventricular event occurs after the reconﬁrmation window, it is classiﬁed as

normal

, and the ICD starts a new reconﬁrmation window. If the event occurs during the reconﬁrmation window, it also falls within the refractory period, and is therefore classiﬁed as

refractory

. If this occurs, the refractory period is terminated, and the ICD starts a new reconﬁrmation window.

Subsequent ventricular events during synchronization start new reconﬁrmation intervals. A sensed event starts a 120 ms post-sense blanking period and a reconﬁrmation window. Paced events start a programmed post-shock a refractory period of up to the same duration (

Pace Blank period, a reconﬁrmation window, and

VT Interval

plus 60 ms).

VF is reconﬁrmed and the ICD delivers the deﬁbrillation therapy synchronized with the second arrhythmic ventricular event. However, if four normal ventricular intervals occur without reconﬁrming VF, the ICD aborts the shock (see Figure 5-7).

Bradycardia Pacing During Reconﬁrmation – Each reconﬁrmation interval also begins an escape period in the VVI mode. If the escape period times out, the ICD paces the ventricle and continues to monitor for reconﬁrmation of VF. VF cannot be reconﬁrmed on an event that immediately follows a paced event, because a refractory period of up to 60 ms plus the programmed

VT Interval

follows a paced event (see

Figure 5-7).

Or VF Interval, if VT Detection is Off

GEM®III VR System Reference Guide

5-13

Tachyarrhythmia Therapies

Deﬁbrillation

At the second arrhythmic event, the shock is delivered

and an extended brady escape period begins.

The ﬁrst event after

charge end is refractory.

C E

300 ms

Blanking

Refractory

Reconﬁrmation

The refractory period can last as long as the VT Interval plus 60 ms, but will terminate with the ﬁrst ventricular event that falls within it.

VT Interval plus 60 ms

V R

120 ms

460 ms

Figure 5-6. Deﬁbrillation Delivered After Reconﬁrming VF

The VF has terminated spontaneously after it was detected.

A paced event occurs, followed by the

programmable pace blanking period

and a refractory period of 460 ms

(TDI plus 60 ms).

If necessary, the device delivers

120 ms 520 ms

1200 ms brady escape interval

a VVI pacing pulse.

After four normal intervals, the

deﬁbrillation therapy aborts.

V P

240 ms

200 ms

C E

Blanking

Refractory

300 ms 120 ms 240 ms

Reconﬁrmation

The refractory period can last as long as

the TDI plus 60 ms but will terminate with

V R

460 ms

the ﬁrst ventricular event that falls within it.

TDI plus 60 ms

Figure 5-7. Deﬁbrillation Aborts After Failure to Reconﬁrm

5-14

GEM®III VR System Reference Guide

V S

V P

V S

120 ms 120 ms120 ms

460 ms

Each event generates a new 460 ms reconﬁrmation interval,

but the VF is never reconﬁrmed during any of them.

V S

200 ms

Cardioversion

Tachyarrhythmia Therapies

Cardioversion

Table 5-4. Cardioversion Programmable Parameters

VT (or FVT) Therapy Status

Therapy Type

Energy (J)

Pathway

Progressive Episode Therapies

Any of the six VT or six FVT therapies can be programmed Off. The ICD retains the settings, but skips the “off” therapy and immediately delivers the next available therapy.

On or Off

0.4 – 30 (see page 5-7)

AX>B or B>AX (see page 5-8)

On or Off (see page 5-33)

Programming Cardioversion Therapies

If VT or FVT Therapy is programmed On, VF Therapy must also be On.

At least one therapy for VT and one therapy for FVT should be programmed to 30 joule cardioversion.

The programmer requires that if FVT therapies are On, then at least one must be programmed to cardioversion (any energy).

If the Progressive Episode Therapies feature is enabled, the ICD may deliver a cardioversion therapy at a higher energy level than was programmed. This ensures that each therapy delivered during an ongoing episode is at least as aggressive as the previous therapy (see “Progressive Episode Therapies” on page 5-33).

GEM®III VR System Reference Guide

5-15

Tachyarrhythmia Therapies

Cardioversion

♦

To Program Cardioversion Therapies

1. Select the Params icon, and choose the Therapies menu option.

2. Select either the [FVT] or [VT] (see Figure 5-8).

3. Set Therapy Type to CV (Therapy Status also turns On).

4. Set Energy and Pathway parameters for each cardioversion therapy.

5. Select [PROGRAM].

VT Therapy Screen

Selected

Cardioversion

Parameters

Figure 5-8. Programmable Cardioversion Parameters

5-16

GEM®III VR System Reference Guide

Tachyarrhythmia Therapies

Cardioversion

6. To program the Progressive Episode Therapies feature, select

[Shared] (see Figure 5-9).

7. Choose a setting for Progressive Episode Therapies.

8. Select [PROGRAM].

Shared Therapy Parameters

Screen Selected

Progressive Episode

Therapies Parameter

Figure 5-9. Shared Therapy Parameters Screen

Cardioversion Synchronization

In general, a cardioversion therapy is synchronized to a non-refractory arrhythmic event, but it aborts if the tachycardia terminates spontaneously.

Cardioversion uses a sequence of synchronization “windows,” each lasting 60 ms plus the programmed

VT Interval

tachyarrhythmia. The ICD deﬁnes a non-refractory sensed ventricular event within this window as

arrhythmic

for synchronization purposes. The ﬁrst synchronization window begins after the 300 ms post-charge blanking period, with an effective refractory period of 100 ms.

, to identify an ongoing

The ICD delivers the cardioversion therapy on a ventricular event that:

■

is non-refractory and arrhythmic, and

■

is not the ﬁrst arrhythmic event during synchronization.

If a synchronization window expires without a ventricular event, the shock aborts at the next event or escape period timeout (see Figure 5-10). The shock also aborts if three consecutive ventricular events are sensed during refractory periods.

Or VF Interval, if VT Detection is Off.

GEM®III VR System Reference Guide

5-17

Tachyarrhythmia Therapies

Cardioversion

This sensed beat generates a second

synchronization window of 460 ms.

Any other refractory or arrhythmic ventricular event begins a new synchronization window, with a 120 ms post-sense blanking period and a 200 ms refractory period.

Bradycardia Pacing During Synchronization – Each synchronization window begins an escape period in the VVI mode. If the escape period times out, the ICD aborts the cardioversion therapy and paces, using its standard output settings. The escape period is the current V-V pacing rate (i.e., sensor or programmed lower rate) interval, up to a maximum of 1760 ms.

The next ventricular event comes after the synchronization window has

timed out, and the cardioversion therapy aborts.

V R

200 ms

460 ms (TDI plus 60)

Blanking

Refractory

Synchronization

C E

300 ms 120 ms 120 ms

400 ms

Figure 5-10. Cardioversion Aborts After Failure to Reconﬁrm

V S

200 ms

A post-sense or post-pace blanking period begins when the shock aborts. The programmed pacing mode also resumes.

5-18

GEM®III VR System Reference Guide

Medtronic 7231CX Reference Guide

Specifications and Main Features

Frequently Asked Questions

User Manual

Introduction

Education

Technical Support

References

Notice

Abbreviations and Acronyms

Primary Capabilities

Pacing Management

Tachyarrhythmia Detection

Tachyarrhythmia Therapy

Patient Management

Other features

Physical Characteristics

Electrical Characteristics

Longevity

Battery Voltage

Charge Time

High Voltage Therapy Energy

Magnet Application

Emergency Settings

Programmable Parameters Overview

Detection Parameters

Therapy Parameters

Bradycardia Pacing Parameters

Data Collection Parameters

Patient Information Parameters

EP Studies Parameters

Fixed Parameters

Notes

Overview

Effect on System Operation

Temporary Parameter Values

Emergency Cardioversion

Emergency Fixed Burst Pacing

Emergency VVI Pacing

System Description

Detection and Therapy Overview

Redetection

Therapy

Suspending Detection and Therapy

Automatic Suspension of Detection

Disabling Detection and Therapies

Sensing

Programming for Appropriate Sensing

Ventricular Sensing

Auto-Adjusting Sensitivity Thresholds

Blanking Periods

Refractory Periods

VF Detection

Programming VF Detection

How VF Detection Works

VF Interval Criterion

VT Detection

Programming VT Detection

How VT Detection Works

VT Interval Criterion

Combined Count Detection

How Combined Count Detection Works

VT Stability Option

Programming VT Stability Option

How the VT Stability Option Works

EGM Width Criterion

Programming the EGM Width Criterion

How the EGM Width Criterion Works

Measuring a QRS Complex

Classifying the QRS Complex

Classifying the Episode

FVT Detection

Programming FVT Detection

How FVT Detection Works

FVT Detection Via VF

FVT Detection Via VT

Combined Count Detection of FVT

Zone Merging After Detection

Termination and Redetection

Outcome Monitoring