Implantable cardioverter-defibrillators in hypertrophic cardiomyopathy

Abstract

Background: Hypertrophic cardiomyopathy is a genetic disease inherited as an autosomal dominant trait associated with risk of sudden death. The majority of cases of sudden death occur in young adults with no or few symptoms, which underlines the importance of risk stratification as a basis for selecting a therapeutic strategy. Implantable cardioverter-defibrillators are indicated in patients resuscitated following cardiac arrest, and those with sustained ventricular tachycardia or two or more risk factors identified in non-invasive tests.

Aim: The aim of this study was to determine the number of appropriate therapies (anti-tachycardia pacing and defibrillation) and the risk factors, or association of risk factors, that predict therapies in patients with hypertrophic cardiomyopathy and an implantable cardioverter-defibrillator.

Methods: We studied 17 consecutive patients with hypertrophic cardiomyopathy and cardioverter-defibrillators implanted between December 1992 and June 2003. The following risk factors were analyzed: 1) previous cardiac arrest or sustained ventricular tachycardia; 2) family history of sudden cardiac death; 3) high-risk genetic mutations; 4) syncope; 5) non-sustained ventricular tachycardia; 6) hypotensive response to exercise; and 7) marked left ventricular hypertrophy. Appropriate therapies were determined and the predictive value of the different sudden death risk stratification parameters was analyzed.

Results: During a mean follow-up of 40 +/- 29 months, 7 patients (41%) received a total of 293 appropriate therapies. Of the 9 patients with previous cardiac arrest or ventricular tachycardia, 4 received appropriate therapies. In the remaining 8 patients, with implantable cardioverter-defibrillators for primary prevention, 3 received appropriate therapies. Family history of sudden death was associated with a positive predictive value of 25% for appropriate therapies, 40% for syncope and 50% for non-sustained ventricular tachycardia. The presence of any two risk factors was associated with a positive predictive value of 33% and the presence of three factors with 100%.

Conclusion: In this group of patients, considered to be at high risk for sudden cardiac death, a considerable percentage had ventricular tachycardias that were correctly identified and treated by the implantable cardioverter-defibrillator. The percentage of patients with appropriate therapies was slightly higher in the group who had a cardioverter-defibrillator for secondary prevention of sudden death (aborted sudden death or sustained ventricular tachycardia). In patients with an implantable cardioverter-defibrillator for primary prevention, non-sustained ventricular tachycardia was the risk factor with the highest predictive value. An association of risk factors was also predictive of arrhythmic events.