Hypertrophic cardiomyopathy (HCM) is a genetic disorder with autosomal-dominant inheritance but variable penetrance. There is thickening of the left ventricle and septum. The disorder causes diastolic dysfunction and can result in a diverse clinical course including heart failure, stroke, and sudden death. While many patients with HCM remain asymptomatic, it is not uncommon for patients to develop symptoms of heart failure, palpitations, chest pain, or syncope. The murmur of HCM is a systolic crescendo-decrescendo, radiating to the axilla/base. It increases with Valsalva or standing, and decreases with squatting.
Dilated cardiomyopathy is the most common type and is characterized by dilation and impaired contraction of one or both ventricles. Causes include genetic abnormalities, alcohol abuse, peripartum, chemotherapy toxicity, and endocrinopathies; it may be idiopathic. Affected patients have impaired systolic function and may develop heart failure. On echocardiogram there is decreased wall thickness, decreased ejection fraction, and increased left ventricular volume.
Restrictive cardiomyopathy results from fibrosis or infiltrative disease of the myocardium, with the most frequent cause being amyloidosis. The left ventricular chamber size is usually normal, but rigid walls are noted with echocardiogram. There is impaired diastolic filling with preserved systolic functioning. Patients typically present with symptoms of heart failure. Myocardial biopsy or cardiac MRI may be recommended to confirm amyloid etiology.