Failure Rate of Implantable Cardioverter-Defibrillators in Apical Hypertrophic Cardiomyopathy
Implantable cardioverter-defibrillators (ICDs) in patients with apical hypertrophic cardiomyopathy have an overall complication rate of approximately 4% per year, with inappropriate shock rates of 3.7% per year and device-related complications occurring at 3.6% per year. 1, 2
Device Effectiveness and Failure Rates
Appropriate Interventions
- ICDs successfully abort life-threatening arrhythmias in HCM patients with an annualized appropriate intervention rate of 6.8% per year 2
- Primary prevention patients have appropriate ICD interventions at a rate of approximately 4% per year 3
- Secondary prevention patients (those with prior cardiac arrest or sustained VT) have a significantly higher rate of appropriate interventions at approximately 10% per year 1
Inappropriate Interventions
- Approximately 25% of HCM patients with ICDs experience inappropriate discharges 1
- The annualized rate of inappropriate ICD interventions is 3.7% per year 2
- Common causes of inappropriate shocks include:
- Supraventricular arrhythmias
- Sinus tachycardia
- Lead fractures or dislodgment
- Oversensing
- Double counting
- Programming malfunctions 1
Device-Related Complications
- Overall device-related complications occur at a rate of 4% per year in HCM patients 1
- Specific complication rates include:
Special Considerations for Apical HCM
While specific data on ICD failure rates in the apical variant of HCM is limited, several important points should be considered:
- Apical HCM patients are often considered lower risk for sudden cardiac death compared to other HCM variants, but the risk is not negligible 4
- Recent evidence suggests that ventricular tachycardia (VT) rather than ventricular fibrillation (VF) is the most common arrhythmia in HCM patients (70% of cases), and is amenable to antitachycardia pacing (ATP) 5
- ATP successfully terminates 79% of VT events in HCM patients 5
- Patients with apical HCM who develop atrial fibrillation have approximately a 2-fold higher risk of sudden death compared to HCM patients without AF 6
Factors Affecting Device Performance
Patient-Related Factors
- Age: Younger patients have higher rates of lead complications due to activity level and body growth 1
- Gender: Male gender is associated with higher rates of appropriate ICD interventions (HR 3.3) 2
- Heart failure status: NYHA class III/IV is associated with higher cardiac mortality (HR 5.2) 2
- Ventricular function: Decreased LV ejection fraction and increased LV dimensions are associated with higher risk of sustained monomorphic VT 5
Device-Related Factors
- Industry-related recalls have included defective generators leading to deaths and small-diameter high-voltage leads prone to fracture 1
- Patients with extreme hypertrophy or those on amiodarone may require high-energy output generators or epicardial lead systems 1
Long-Term Outcomes After ICD Therapy
- Post-ICD intervention, freedom from HCM mortality is 100%, 97%, and 92% at 1,5, and 10 years, which is better than in ischemic or nonischemic cardiomyopathy ICD trials 7
- The majority (85%) of HCM patients remain in NYHA class I/II without significant change in clinical status over 5.9±4.9 years after appropriate ICD interventions 7
- Despite heightened anxiety about future shocks, HCM patients with ICDs maintain intact general psychological well-being and quality of life 7
Clinical Implications
- For patients with apical HCM, the decision for ICD implantation should be based on established risk factors for SCD in HCM, with recognition that even "low-risk" apical HCM patients may experience life-threatening arrhythmias 4
- ATP-capable devices should be considered in HCM patients, particularly those with decreased LV ejection fraction and increased LV dimensions 5
- Younger patients require more vigilant monitoring for lead-related complications 1
- Regular device interrogation is essential to detect and address potential device issues before clinical manifestations