21.4: Cardiomyopathy IV: Restrictive Cardiomyopathy

Restrictive cardiomyopathy (RCM) is a rare heart muscle disease characterized by impaired ventricular filling due to stiffened ventricular walls, leading to significant diastolic dysfunction.

Etiology

Restrictive cardiomyopathy can arise from both inherited and acquired diseases, many of which are systemic. It is categorized into four main types: infiltrative, storage, non-infiltrative, and endomyocardial diseases.

• Infiltrative diseases, such as amyloidosis, lead to RCM by depositing amyloid proteins between the heart muscle cells, disrupting their function.
• Storage diseases, like hemochromatosis, involve iron accumulation within the heart muscle, causing stiffness and impaired contraction. Hemochromatosis is often due to genetic mutations in the HFE gene and affects multiple organs, including the heart.
• Non-infiltrative diseases, such as scleroderma, cause RCM through fibrosis and stiffening of the heart tissue. This process affects the heart's ability to relax and fill properly during diastole.
• Endomyocardial diseases include damage from cancer treatments like certain chemotherapeutic agents, such as anthracyclines and radiation. These treatments can lead to scarring and fibrosis of the endocardium and myocardium, further restricting cardiac function.

Pathophysiology

The pathophysiology of restrictive cardiomyopathy (RCM) involves reduced ventricular

compliance, often due to fibrosis or infiltration of the ventricular walls. Fibrosis indicates the thickening and scarring of connective tissue, often due to chronic injury or inflammation. Infiltration involves the accumulation of abnormal substances or cells in the ventricular walls, such as amyloid proteins in amyloidosis. This results in stiffened ventricular walls, leading to elevated filling pressures and impaired diastolic filling. As a result, cardiac output is reduced, and pulmonary venous pressures increase, causing pulmonary congestion and heart failure symptoms.

Clinical Manifestations

Clinical manifestations of RCM include fatigue, exercise intolerance, and dyspnea. Additional symptoms may involve angina, orthopnea, syncope, and palpitations. The patient may present with signs of heart failure, including dyspnea, peripheral edema, ascites, hepatomegaly, and jugular venous distention.

Diagnostic Studies

Diagnosing RCM involves chest X-rays, which may be normal or show cardiomegaly from atrial enlargement, echocardiography to assess diastolic function and atrial size, cardiac MRI to identify specific infiltrative or fibrotic processes, and sometimes endomyocardial biopsy to determine the exact cause. Advanced echocardiographic techniques, like strain imaging, can provide additional insights into myocardial function.

Interprofessional Care

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

Summary

In summary, RCM is characterized by stiffened ventricular walls that lead to diastolic dysfunction and heart failure symptoms. Diagnosing RCM involves imaging and biopsy, while management focuses on treating the symptoms and addressing the underlying cause.