Hypertrophic cardiomyopathy is regarded as the most common cause of sudden 
cardiac death in young people (including trained athletes). Introduction of 
implantable cardioverter-defibrillators to the hypertrophic cardiomyopathy 
patient population represents a new paradigm for clinical practice and perhaps 
the most significant advance in the management of this disease to date. 
Implantable defibrillators offer the only proven protection against sudden death 
by virtue of effectively terminating ventricular tachycardia/fibrillation and, 
in the process, altering the natural history of hypertrophic cardiomyopathy and 
providing the potential opportunity of normal or near-normal longevity for many 
patients. However, targeting the most appropriate candidates for prophylactic 
device therapy can be complex, compounded by the unpredictability of the 
underlying arrhythmogenic substrate, absence of a single dominant and 
quantitative risk marker in this heterogeneous disease, and the historical 
difficulty in assembling sufficiently powered prospective and randomized trials 
in large patient populations. Nevertheless, the current risk factor algorithm, 
when combined with a measure of individual physician judgment, is an effective 
strategy for identifying high-risk patients. Indeed, prevention of sudden death 
has now become an integral, albeit challenging, component of overall 
hypertrophic cardiomyopathy management.