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The Long-Term Survival and the Risks and Benefits of Implantable Cardioverter Defibrillators in Patients With Hypertrophic Cardiomyopathy
Study Questions:
What is the long-term morbidity and mortality associated with implantable cardioverter-defibrillators (ICDs) in patient with hypertrophic cardiomyopathy (HCM)?
Methods:
This was a single-center retrospective analysis of 334 patients with HCM who underwent ICD implant. ICDs were placed for primary and secondary prevention. Indications for primary prevention ICD implant included a family history of sudden cardiac death, mid left ventricular wall thickness ≥30 mm, nonsustained ventricular tachycardia on Holter monitor, or abnormal blood pressure response on stress testing. There were five endpoints: first appropriate ICD shock, first inappropriate shock, implant-related complication, any adverse ICD-related event (inappropriate shock and/or complication of device implant), and cardiovascular mortality. The primary outcomes of interest were assessed using Cox modeling (hazard ratio [95% confidence interval] provided).
Results:
ICDs were placed for primary prevention in 92% (n = 307) of patients. Systolic function was normal in 301 (90%) of patients. Mortality was 7% (n = 22) over a median follow-up of 3.6 years [interquartile range, 1.8-5.2]; two deaths occurred due to device implant complications. Appropriate ICD shocks occurred at a rate of 2.3%/year (5-year cumulative incidence 13%), with the first shock occurring a median of 2.1 years after device implant. Reduced fractional shortening at implant was associated with both increased mortality and appropriate ICD therapies. Adverse ICD events occurred in 30% of patients at a rate of 8.6% and 34% at 1 and 5 years following implant, respectively. Inappropriate ICD shocks (n = 55 patients) occurred at a rate of 4.6%/year (21% cumulative incidence at 5 years), and 31% of patients who sustained inappropriate shocks had a recurrent inappropriate event. Seventy-three implant-related complications occurred in 18% (n = 60) of the cohort (21% 5-year cumulative incidence). Lead failure, lead displacement, and pocket infection were the most common complications. There were no significant predictors of ICD complications.
Conclusions:
The authors concluded that HCM patients have high rates of cardiovascular mortality, but also face the burden of ICD complications.
Perspective:
This is an excellent and much needed analysis of ICD therapy in HCM patients. The authors followed current guidelines for ICD implant, and demonstrated appropriate therapy in just under 25% of patients after 5 years of implant. This number does not include patients who received antitachycardia pacing without defibrillation. The authors point out that appropriate ICD therapy should not be equated to ‘prevention of sudden cardiac death,’ and this is even more applicable for the association of antitachycardia pacing therapy and sudden cardiac death. However, the burden of arrhythmias in this cohort is well demonstrated in this study. Unfortunately, the burden of inappropriate therapies is also great for HCM patients. The authors could not demonstrate that dual-chamber devices afforded less inappropriate therapy than single-chamber ICDs. Supraventricular arrhythmias and sinus tachycardia were the most common causes for inappropriate device discharge, highlighting a possible need for more aggressive beta-blocker titration, consideration for atrioventricular node ablation, or better device algorithms for arrhythmia discrimination.
Keywords: Cardiomyopathy, Hypertrophic, Electric Countershock, Blood Pressure, Primary Prevention, Tachycardia, Ventricular, Secondary Prevention, Tachycardia, Sinus, Heart Failure, Electrocardiography, Ambulatory, Confidence Intervals, Defibrillators, Implantable, Death, Sudden, Cardiac, Atrioventricular Node
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