*Restrictive Cardiomyopathy

Definition, Etiology, PathogenesisTop

Restrictive cardiomyopathy (RCM) is a disease of the myocardium characterized mainly by left ventricular (LV) diastolic dysfunction. RCM may be familial (eg, inherited defects in desmin or troponin I) or caused by systemic disorders (eg, amyloidosis, sarcoidosis, scleroderma, carcinoid disease, radiation, and endomyocardial fibrosis caused by hypereosinophilic syndrome or drugs such as serotonin or ergotamine).

Clinical Features and Natural HistoryTop

Manifestations of RCM include dyspnea, fatigue, and in more advanced disease also features of right ventricular dysfunction. The natural history of RCM largely depends on its etiology and severity of myocardial changes.

DiagnosisTop

Diagnostic Tests

1. Electrocardiography (ECG) may reveal abnormal P waves, a low R-wave amplitude, flat T waves, and supraventricular arrhythmias, especially atrial fibrillation. In amyloid cardiomyopathy, ECG typically has low voltages due to infiltration of amyloid.

2. Echocardiography may reveal normal or increased LV wall thickness, enlargement of both atria with relatively small ventricles, normal or slightly impaired systolic function of the ventricles, and diastolic LV dysfunction. Tissue Doppler echocardiography can be useful to differentiate between RCM and constrictive pericarditis.

3. Heart catheterization is performed in case of difficulties in differentiating between RCM and constrictive pericarditis.

4. Endomyocardial biopsy is performed in the case of suspected myocardial infiltrates caused by amyloidosis, sarcoidosis, idiopathic eosinophilia, or hemochromatosis.

5. Cardiac magnetic resonance imaging (MRI) may be useful in differentiating underlying etiologies such as sarcoidosis, amyloidosis, endomyocardial fibrosis, or eosinophilia.

6. Cardiac 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) may be useful in the diagnosis and assessment of treatment response in sarcoidosis.

Diagnostic Criteria

RCM is diagnosed on the basis of imaging studies and in some cases on the basis of histologic examination of cardiac biopsy specimens.

Differential Diagnosis

RCM should be mainly differentiated from constrictive pericarditis. This usually requires a specialized cardiology assessment and may involve invasive testing.

TreatmentTop

1. Symptomatic treatment: As in chronic heart failure.

2. Long-term anticoagulation is used in patients with atrial fibrillation.

3. Heart transplantation is used in end-stage heart failure not responding to treatment.

4. Treatment of the underlying condition is used in patients with potentially reversible causes.

Special ConsiderationsTop

1. Cardiomyopathy associated with hemochromatosis may lead to heart failure but frequently causes only minor symptoms. Treatment is with phlebotomy.

2. Cardiomyopathy associated with amyloidosis develops in 50% of patients with AL amyloidosis, 10% of patients with AA amyloidosis, and rarely in those with familial disease. Amyloid deposits lead to significant cardiac dysfunction and wall thickening, causing features of restriction and diastolic LV dysfunction, as well as to reduced right ventricular function. Amyloidosis also leads to arrhythmia, conduction disease, and a tendency to orthostatic hypotension. It must be suspected in the case of RCM developing in a person with proteinuria, hepatomegaly, anemia, or a chronic inflammatory condition. Echocardiographic features include marked hypertrophy of the ventricles, diastolic dysfunction with or without LV systolic dysfunction, biatrial enlargement, interatrial hypertrophy, and pericardial effusion. Diagnosis may be confirmed with biopsy of the abdominal fat pad, gingiva, rectum, or affected organ. Chemotherapy is available for patients with AL amyloidosis associated cardiomyopathy. Caution is noted with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, digoxin, beta-blockers, and calcium channel blockers, given their predisposition to cause hypotension in patients with this disease. Beta-blockers can be used, however, in the context of atrial fibrillation to improve diastolic filling time. Otherwise, careful use of diuretics is the pharmacotherapy of choice.