Hypertrophic cardiomyopathy is a genetic disease that affects the cardiac 
sarcomere, resulting in myocardial hypertrophy and disarray. Affected patients 
have a predisposition for malignant ventricular tachyarrhythmias and, 
consequently, sudden cardiac death. With the availability of therapeutic 
measures that prevent sudden death, the identification of high-risk patients is 
now of greater importance. Clinical risk factors for sudden death (ie, age, 
syncope, family history of sudden cardiac death, cardiac arrest survivor, 
nonsustained ventricular tachycardia and abnormal blood pressure response to 
exercise) have been identified. The clinical electrophysiological study is of 
limited use for stratifying these patients. More recently, increased attention 
has been given to the degree of echocardiographically documented left 
ventricular hypertrophy and prognostically significant genetic mutations. Once a 
high-risk patient is identified, prophylactic treatment is warranted. For this 
purpose, amiodarone has been supplanted by the implantable 
cardioverter-defibrillator. Implantable cardioverter-defibrillator treatment 
appears to reduce the risk of sudden cardiac death in both primary and secondary 
prevention settings. Thus, tools are now available to identify and treat 
high-risk patients with hypertrophic cardiomyopathy.