Role of Implantable Cardioverter Defibrillators (ICDs) in Preventing Sudden Cardiac Death, Slides of Medicine

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ICD’s: Current Roles and

Evidence

Learning Objectives

• Brief history of the ICD
• Review of the prevalence of Sudden Cardiac Death.
• Gaining familiarity with major trials that went into the current guidelines of ICD placement. - Secondary Prevention - Primary prevention in Heart Failure - Ischemic - Non Ischemic
• Familiarity with the latest guidelines for ICD placement.
• Briefly discuss CRT
• We will not talk about ethical or economic issues.

The first ICD

• Because of Dr. Mirowski:
• In 1980, the first patient received an ICD at Johns Hopkins Hospital.
• 1985: FDA approves sale and use of ICD’s

Evolution of ICD’s

• First ICD’s required a thoracotomy and used epicardial leads.
• The device was so large, that it needed to placed in the abdomen.
• Invention of transvenous defibrillator in 1969 allowed for a great reduction in ICD size, and made Mirowski’s idea practicle.

ICD

Road to ICDs

The Problem: Sudden Cardiac Death

• In the United States, accounts for 325, deaths per year.
• Often the first presentation of heart disease.
• More often than not, occur in people with structural heart or coronary disease.
• Out of hospital cardiac arrests are unlikely to survive (rates from 1.4 - 20%). Those who do survive are often not neurologically intact.

Secondary Prevention

• ICD’s first treatment group to be studied were those had already suffered a VF or VT event.
• Important trial
  • AVID
• Preceding AVID (smaller trials)
  • CASH - Cardiac Arrest Survival in Hamburg (349 subjects)
  • CIDS – Canadian Implantable Defibrillator Study (659 subjects)
  • The above two showed trends, but not signifcance towards less mortality with ICD’s (underpowered)

AVID trial

• 1013 study subjects received either an ICD or medical thearpy (sotalol or amiodarone)
• There was crossover both ways of 20% (either ICD’s or antiarrythmics added).
• Study terminated early due greatly improved outcome in ICD group.
  • Survival

Antiarrythmics ICD Year 1 82.3 % 89.3 % Year 2 74.7 % 81.6 % Year 3 64.1% 75.4 %

AVID trial

Primary Prevention

• As so many patients do not survive SCD neurologically intact or at all, there was a focus to investigate which groups of patients would benefit from ICD’s as primary prevention.
• Focus of investigation
  • High risk (Brugada syndrome, long qt syndrome, Arrythmogenic Right Ventricular dysplasia)
  • Cardiomyopathy (Ischemic or Nonischemic)

ICD’s as primary prevention:

Ischemic Cardiomyopathy

MADIT I

• 196 patients who had
  • Prior MI AND
  • NYHA class I, II, or III AND
  • NSVT AND
  • LV dysfunction (LVEF 35%) AND
  • Inducible VT despite procainamide
• Randomly assigned to ICD, antiarrythmic drug.

MADIT I

• 196 patients enrolled
• 15 deaths in ICD group (N = 101) vs 39 in conventional therapy (N=95).
• ICD reduced overall mortality by 54% and arrhythmic mortality by 75% compared to antiarrythmic therapy
• Mean followup was 27 months