Cardiomyopathy IV: Restrictive Cardiomyopathy

Restrictive cardiomyopathy develops from infiltrative diseases like amyloidosis, which deposits amyloid proteins between heart muscle cells, or storage diseases such as hemochromatosis, which causes iron accumulation in the heart. Non-infiltrative diseases like scleroderma cause fibrosis and stiffening. Endomyocardial diseases result from chemotherapy or radiation damage, leading to scarring and fibrosis that restricts cardiac function.

Stiffened ventricular walls reduce ventricular compliance, impairing the heart's ability to relax and fill during diastole. This increases filling pressures and decreases cardiac output. Pulmonary venous pressures rise, causing pulmonary congestion and heart failure symptoms including fatigue, dyspnea, and exercise intolerance.

Patients with restrictive cardiomyopathy experience fatigue, exercise intolerance, dyspnea, angina, orthopnea, and palpitations. Physical examination may reveal signs of heart failure such as peripheral edema, ascites, hepatomegaly, and jugular venous distention. Syncope may also occur in severe cases of the disease.

Diagnosis involves chest X-rays to detect cardiomegaly from atrial enlargement, echocardiography to assess diastolic function and atrial size, and cardiac MRI to identify infiltrative or fibrotic processes. Advanced echocardiographic techniques like strain imaging provide additional insights into myocardial function. Endomyocardial biopsy may determine the exact underlying cause.

Infiltrative diseases like amyloidosis deposit abnormal proteins between heart muscle cells, disrupting function. Storage diseases like hemochromatosis involve accumulation of substances, typically iron, within the heart muscle itself. Both cause ventricular stiffness and impaired relaxation, but through different pathophysiological mechanisms affecting cardiac compliance.

Management focuses on treating the underlying cause and relieving symptoms. Specific treatments include chemotherapy for amyloidosis or immunosuppressive therapy for sarcoidosis. Anticoagulation is often required due to increased thromboembolic risk from atrial enlargement. In severe cases unresponsive to medical therapy, heart transplantation may be necessary.

Restrictive cardiomyopathy is characterized by stiffened ventricular walls causing diastolic dysfunction, unlike dilated cardiomyopathy which involves chamber enlargement, or hypertrophic cardiomyopathy which features wall thickening. RCM primarily impairs ventricular filling and relaxation, leading to elevated filling pressures and reduced cardiac output despite relatively normal wall thickness.