Implantable Cardioverter

Defibrillators (ICDs)

Dr. Prithvi Puwar

DNB Cardiology Registrar

Vijaya Hospital, Chennai

Presentation will cover:

• History of ICDs

• Indications for ICDs

• Major Trials

Pioneers of ICDs - “M&M”

Martin Mower

Michel Mirowski

*Dr Chow Wei En©

*

EVOLUTION OF ICDs:

1947 First human internal defibrillation

1956 First human external defibrillation

1969 First external canine prototype tested

1970 First implantable prototype (895 g)

1975 First implantable Defibin canines (250 g)

1980 First human implant @ Johns Hopkins

1985 ICD market released (350 units)

1991 Non thoracotomy lead systems

1995 Pectoral ICD systems

1997 ICD & DDD

1999 ICD & Atrial Defibrillation

2001 ICD & Resynchronization Therapy

Components of ICD –

1. Device

• Battery, Capacitors & Voltage

• Circuitry

• Connector Blocks

2. Leads

• Transvenous / Epicardial

• Electrical Design

• Connectors: IS-1 & DF-1

3. Programmer

Ventricle

VT prevention

Anti-tachycardia pacing

Cardioversion

Defibrillation

Atrium & Ventricle

Bradycardia sensing

Bradycardia pacing

Anti-tachycardia pacing

USES OF ICDs:

Secondary prevention:

prior episode of resuscitated

VT/VF or sustained

hemodynamically unstable VT

episodes of spontaneous

sustained VT in the presence of

heart disease (valvular, ischemic,

hypertrophic, dilated, or infiltrative

cardiomyopathies) and other

settings (eg, channelopathies)

Primary prevention:

prior myocardial infarction (at least

40 days ago) and LVEF ≤35%

cardiomyopathy, NYHA II to III with

LVEF<35%

syncope who have structural heart

disease and inducible VT/VF

Long QT, Torsades on Rx,

Brugada, ARVD, HCM

When ICD therapy is not indicated

• ventricular tachyarrhythmias due to a completely reversi

ble disorder in the absence of structural heart disease

(electrolyte imbalance, drugs, or trauma)

• No reasonable expectation of survival with acceptable

functional status for at least one year

• significant psychiatric illnesses that may be aggravated

by device implantation

• Patient with VF or VT amenable to surgical or catheter a

blation (WPW, LVOT VT)

Indications for ICDs (ACC)

ICD Programming and therapy:

Contemporary ICDs have a variety of flexible programming

and therapeutic options:• Arrhythmia discrimination – ability to distinguish arrhythmias

requiring ICD therapy from other heart rhythms

• Multiple available therapies – anti-tachycardia pacing and/or

shock

• Sequential therapies - In each therapy zone, a sequence of up

to five or six therapies (bursts of anti-tachycardia pacing,

cardioversion, or defibrillation) can be delivered. After each

therapy, the device reevaluates the rhythm, and if the

tachyarrhythmia persists, the next therapy is delivered.

About medical therapy

first?

SCD Prevention Trials -

Antiarrhythmic Agents

• CAST I [Cardiac Arrhythmia Suppression Trial (1991)]

• ESVEM [Electrophysiologic Study vs ECG Monitoring (1993)]

• GESICA [Grupo de Estudio de la Sobrevida en la Insuficiencia

Cardiaca en Argentina (1994)]

• CHF STAT [Congestive Heart Failure: Survival Trial of

Antiarrhythmic Therapy (1995)]

• SWORD [Survival with Oral d-Sotalol (1996)]

• CAMIAT [Canadian Amiodarone Myocardial Infarction

Arrhythmia Trial (1997)]

• EMIAT (European Myocardial Infarction Amiodarone Trial

(1997)]

Multicenter,

randomized, double-

blind, placebo-controlled

Patients: 1725

pts with >6 ventricular

premature

depolarizations/h and

LVEF<0.55 at <90 days

after MI or <0.40 at >90

days after MI

Follow up and primary

end point:

Mean 10 months follow

up.

Primary endpoint death

from arrhythmia

CHF STAT

SWORD Trial

EMIAT (European MI Amiodarone

Trial)

There was no difference in the primary endpoint of all-cause mortality (P=0.95)

However, patients assigned to the amiodarone group did have a statistically

significant reduction in VF or arrhythmic death (4.0% versus 7.9%,P=0.006).

Summary of drug trials:

1. Anti-arrhythmics may worsen the survival

2. Amiodarone may slightly improve the outcome

SCD Prevention Trials - ICDs• Secondary Prevention

• CASH [Cardiac Arrest Study Hamburg (1994)]

• AVID [Amiodarone vs Implantable Defibrillator (1995)]

• CIDS [Canadian Implantable Defibrillator Study (2000)]

• Primary Prevention

• MADIT [Multicentre Automatic Defibrillator Implantation Trial (1996)]

• CABG-PATCH (1997)

• MUSTT [Multicentre Unsustained Tachycardia Trial (1999)]

• MADIT II (2002)

• DEFINITE (2004)

• DINAMIT (2004)

• SCD-HeFT (2005)

ICDs in Secondary

Prevention

Key Trials: ICD in Secondary

Prevention

# Mean age 60

# Mostly CAD pts

# Interestingly, in CASH, only VF arrest puts included, and those

that had ICDs implanted did not receive amiodarone, compared to

AVID and CIDS where the ICD arms still had up to 20% of pts on

amiodarone

• Antiarrhythmics vs

ICDs

• First trial of such

nature to be

completed

• Demonstrated

superiority of ICDs

over AADs

(primarily

amiodarone)

AVID Trial

A Comparison of Antiarrhythmic-Drug Therapy with Implantable Defibrillators in Patients Resuscitated from Near-Fatal Ventricular Arrhythmias

The Antiarrhythmics versus Implantable Defibrillators (AVID) Investigators. N Engl J Med 1997; 337:1576-1584

CIDS (Canadian Implantable Defibrillator

Study)

Background: (ICD) terminates VT or VF, but it is not known

whether this device prolongs life in these patients compared with

medical therapy with amiodarone

Conclusions—A 20% relative risk reduction occurred in all-cause

mortality and a 33% reduction occurred in arrhythmic mortality

with ICD therapy compared with amiodarone; this reduction did

not reach statistical significance.

Sub-optimally Addressed Issues

• Beta-blockade - have we really optimised medical therapy prior

to device implantation?

• Is 35% the magic EF?

• Under-represented population - the impact of ICD in non-

ischaemic CMP?

JACC

1999

Are AADs more protective over the long term horizon?

(Results of all three studies are consistent with each other)

Meta-analyses of the ICD Secondary Prevention Trials. Connolly et al. European Heart Journal 2000 (21) 2071-2078

HRS/ACC/AHA Expert COnsensus Statement on the Use of ICD Therapy in Patients who are not included or not well represented in Clinical Trials.

Heart Rhythm 2014; 11:1270-1303

HRS/ACC/AHA Expert COnsensus Statement on the Use of ICD Therapy in Patients who are not included or not well represented in Clinical Trials.

Heart Rhythm 2014; 11:1270-1303

ICDs in Primary

Prevention

Class I Indication? Not always clear

cut…

MADIT II

MADIT I & II

Matching the

Evidence to the

Guidelines

Indications for ICDs (ACC)

SCD HeFT

Indications for ICDs (ACC)

DEFINITE

Indications for ICDs (ACC)

MADIT II

Indications for ICDs (ACC)

MUSTT

MADIT I

Indications for ICDs (ACC)

AVID, CIDS, CASH

Wever EF, Hauer RN, van Capelle FL, et al. Randomized study of implantable defibrillator as first-choice

therapy versus conventional strategy in postinfarct sudden death survivors. Circulation. 1995;91: 2195–203.

• The Grey Zone: 35% < EF < 40%.

• NSVT post MI, EF > 35%

• NSVT post MI, EF > 35% with negative EPS

• NSVT in NICMP

• Elderly - what is the “age cut-off”?

• Beyond EF

• Dual vs Single Chamber; Programming (minimising inappropriate

shocks)

THANK YOU

Unaddressed Scenarios