Cardiomyopathy, hypertrophic
LIFE-THREATENING DISORDERA primary disease of the cardiac muscle, hypertrophic cardiomyopathy is characterized by disproportionate, asymmetric thickening of the interventricular septum in relation to the free wall of the left ventricle (3:1 ratio). With hypertrophic cardiomyopathy—previously known as idiopathic hypertrophic subaortic stenosis— cardiac output may be low, normal, or high, depending on whether stenosis is obstructive or nonobstructive.
The natural history of hypertrophic cardiomyopathy varies. Some patients may remain asymptomatic for years. The dyspnea that results is primarily due to markedly impaired diastolic compliance rather than systolic dysfunction. Sudden death, especially during exercise, may be the initial event, as has occurred with certain athletes (attributed to 36% who died suddenly).
Causes
Despite being designated as idiopathic in almost all cases, hypertrophic cardiomyopathy may be inherited as a non-sex-linked autosomal dominant trait. Most patients have obstructive disease, resulting from effects of ventricular septal hypertrophy and the movement of the anterior mitral valve leaflet into the outflow tract during systole. Eventually, left ventricular dysfunction, from rigidity and decreased diastolic compliance, causes pump failure.
Signs and symptoms
The primary signs and symptoms of hypertrophic cardiomyopathy are exertional dyspnea (90% of patients), angina (75% of patients), and syncope. The chest pain is atypical in that it usually occurs at rest, is prolonged, has no relation to exertion, and isn’t relieved by a nitrate. When sudden death occurs, it may be the first indication of the disease.
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