Restrictive Cardiomyopathy (RCM)

Definition, Etiology, PathogenesisTop

Restrictive cardiomyopathy (RCM) is a disease of the myocardium characterized mainly by left ventricular (LV) diastolic dysfunction. The causes of RCM are heterogeneous and can be divided into primary (idiopathic RCM and endomyocardial fibrosis) or secondary, many of which are infiltrative (amyloidosis, sarcoidosis, hemochromatosis, systemic sclerosis, carcinoid heart disease, storage diseases, and radiation-induced cardiomyopathy).

Clinical Features and Natural HistoryTop

Manifestations of RCM include dyspnea, fatigue, and features of right heart failure. Arrhythmias are common. 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 in limb leads.

2. Echocardiography (Figure 1) 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.

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

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

5. Cardiac 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) may be useful in conjunction with CMR in sarcoidosis, as it can identify active inflammation and inform on response to therapy.

6. Nuclear scintigraphy with technetium-99m pyrophosphate (99mTc-PYP) can be used to detect cardiac amyloid and has the added benefit of distinguishing between the two most common types (immunoglobulin light chain amyloid [AL] and amyloid transthyretin [ATTR]).

7. Endomyocardial biopsy (EMB) is sometimes performed in the setting of suspected infiltrative disease, but the diagnostic yield is low. Noninvasive methods are preferred and EMB should be reserved for cases of diagnostic uncertainty due to equivocal results of noninvasive testing or negative results that are discordant with the degree of clinical suspicion.

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. It is also important to exclude hypertrophic cardiomyopathy and severe hypertensive heart disease.

TreatmentTop

1. Symptomatic treatment: As in chronic heart failure (see Chronic Heart Failure).

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

3. Heart transplant 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 secondary to myocardial deposition of amyloid fibrils, leading to significant wall thickening and causing features of restriction. The clinical presentation includes symptoms of heart failure, orthostatic hypotension, and arrhythmias (both atrial and ventricular). In the case of ATTR, there may be a history of carpal tunnel syndrome, spinal stenosis, or both. Echocardiographic features include marked ventricular hypertrophy, diastolic dysfunction with or without LV systolic dysfunction, biatrial enlargement, and reduced global longitudinal strain with an apical sparing pattern. Once cardiac amyloid is suspected, diagnosis involves screening for amyloid-associated plasma cell dyscrasias (AL) using serum and urine protein electrophoresis and a serum free light chain assay. If a monoclonal protein is identified, urgent hematology referral is warranted. In the absence of a monoclonal protein, a 99mTc-PYP scan should be performed to assess for ATTR. Chemotherapy is available for patients with AL amyloidosis, whereas ATTR can be directly targeted using the stabilizing agent tafamidis. Current guidelines recommend the use of tafamidis in patients with New York Heart Association (NYHA) class I to III symptoms. Caution is advised with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, digoxin, beta-blockers, and calcium channel blockers, given their predisposition to cause hypotension in patients with amyloid cardiomyopathy.

FiguresTop

Figure 3.6-4. Echocardiography (apical 4-chamber view) of a patient with restrictive cardiomyopathy showing significant enlargement of both atriums (LA, left atrium; RA, right atrium). The left ventricle (LV) and right ventricle (RV) are normal sized.