The dilemma of left ventricular outflow tract obstruction and sudden death in hypertrophic cardiomyopathy: do patients with gradients really deserve prophylactic defibrillators?

Abstract

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disease, as well as the most frequent cause of sudden cardiac death in young people including competitive athletes.1 The devastating consequence of sudden death has, in fact, been central to our perception of the natural history of HCM for almost 50 years, as its initial contemporary description by Teare in 1958.1 Now that HCM has assumed an important place in the implantable cardioverter-defibrillator (ICD) era,2 the issue of risk stratification and sudden death prevention has become a major clinical consideration and central to the management of these patients, adding enormously to the complexity of the disease. Indeed, the ICD was initially promoted specifically for HCM in 20002, and subsequently thousands of young patients have been afforded this potentially life-saving therapy. The efficacy of the ICD in HCM, for both secondary and primary prevention, is now well established.2,3 Despite this encouraging development, a mismatch persists between the power of ICD technology to recognize and successfully abort potentially lethal ventricular tachyarrhythmias, and our ability to prospectively identify, with precision, each individual patient who may benefit from a prophylactically implanted device. Indeed, in a heterogeneous disease with a low cardiac event rate such as HCM, decisions regarding sudden death prevention are frequently encumbered by risk profiles of individual patients which fall into uncertain grey areas of ambiguity between high and low risk. At this point, six major risk factors for sudden death have been proposed in HCM, including prior cardiac arrest for which there is general agreement regarding the role of secondary prevention ICDs.1,2,4,5 The five traditional risk markers for primary prevention include: (1) sudden death due to HCM in one or more relatives; (2) massive left ventricular (LV) … ** Corresponding author. Tel: +1 612 863 3996; fax: +1 612 863 3875. E-mail address : hcm.maron{at}mhif.org