CONTEXT: Throughout the past 40 years, a vast and sometimes contradictory 
literature has accumulated regarding hypertrophic cardiomyopathy (HCM), a 
genetic cardiac disease caused by a variety of mutations in genes encoding 
sarcomeric proteins and characterized by a broad and expanding clinical 
spectrum.
OBJECTIVES: To clarify and summarize the relevant clinical issues and to profile 
rapidly evolving concepts regarding HCM.
DATA SOURCES: Systematic analysis of the relevant HCM literature, accessed 
through MEDLINE (1966-2000), bibliographies, and interactions with 
investigators.
STUDY SELECTION AND DATA EXTRACTION: Diverse information was assimilated into a 
rigorous and objective contemporary description of HCM, affording greatest 
weight to prospective, controlled, and evidence-based studies.
DATA SYNTHESIS: Hypertrophic cardiomyopathy is a relatively common genetic 
cardiac disease (1:500 in the general population) that is heterogeneous with 
respect to disease-causing mutations, presentation, prognosis, and treatment 
strategies. Visibility attached to HCM relates largely to its recognition as the 
most common cause of sudden death in the young (including competitive athletes). 
Clinical diagnosis is by 2-dimensional echocardiographic identification of 
otherwise unexplained left ventricular wall thickening in the presence of a 
nondilated cavity. Overall, HCM confers an annual mortality rate of about 1% and 
in most patients is compatible with little or no disability and normal life 
expectancy. Subsets with higher mortality or morbidity are linked to the 
complications of sudden death, progressive heart failure, and atrial 
fibrillation with embolic stroke. Treatment strategies depend on appropriate 
patient selection, including drug treatment for exertional dyspnea 
(beta-blockers, verapamil, disopyramide) and the septal myotomy-myectomy 
operation, which is the standard of care for severe refractory symptoms 
associated with marked outflow obstruction; alcohol septal ablation and pacing 
are alternatives to surgery for selected patients. High-risk patients may be 
treated effectively for sudden death prevention with the implantable 
cardioverter-defibrillator.
CONCLUSIONS: Substantial understanding has evolved regarding the epidemiology 
and clinical course of HCM, as well as novel treatment strategies that may alter 
its natural history. An appreciation that HCM, although an important cause of 
death and disability at all ages, does not invariably convey ominous prognosis 
and is compatible with normal longevity should dictate a large measure of 
reassurance for many patients.