Abbreviation: HCM.
A heart muscle disease of uncertain cause, marked by excessive and disorganized growth of myofibrils, impaired filling of the heart (diastolic dysfunction), a reduction in the size of ventricular cavities, and often, ventricular arrhythmias and sudden death. Examination of the heart by echocardiography or other modalities may show the heart's enlargement to be most pronounced in the interventricular septum. Hypertrophy in that location may limit the flow of blood (and increase pressure gradients) from the left ventricle to the aorta. Abnormal anterior motion of the mitral valve during systole also may be found. These two findings are often designated on echocardiographic reports of patients with HCM by the following abbreviation: ASH-SAM (“asymmetric septal hypertrophy–systolic anterior motion” of the mitral valve).







Figure: CARDIOMYOPATHIES





SYMPTOMS
Although they may be asymptomatic for many years, patients commonly report shortness of breath (especially on exertion), fatigue, atypical chest pain (at rest and after meals), orthopnea, dizziness, and other symptoms of congestive heart failure after the heart muscle markedly enlarges. An S4 and a harsh crescendo-decrescendo systolic murmur, best heard at the left lower sternal border, may be present. Ventricular arrhythmias are common; they may result in palpitations, syncope, or sudden death.

TREATMENT
Drug therapies include beta blocking and calcium channel blocking drugs (such as verapamil) to slow heart rate, control arrhythmias, and reduce myocardial oxygen demand. Anticoagulants and antiarrhythmic agents are used occasionally as well. For patients with marked enlargement of the ventricular septum and high outflow tract pressure gradients (>50 mm Hg), surgical removal of the enlarged muscle or ablation often produces favorable improvements in exercise tolerance and breathing.

PATIENT CARE
Strenuous physical exercise should be discouraged because it may produce breathlessness, presyncope, or frank loss of consciousness. As appropriate, the patient should be encouraged to lose weight, stop smoking, and limit alcohol intake. An implanted cardioverter/defibrillator (ICD) may be required. The patient should be advised to report symptoms of chest pain, prolonged dyspnea, or syncope promptly. Because HCM may be familial in about 25% of patients, first-degree relatives of affected persons should be referred for evaluation.

Main entry:
cardiomyopathy