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Restrictive Cardiomyopathy

By Thomas D. Stamos, MD, Associate Professor of Medicine, Chief, Clinical Cardiology, University of Illinois at Chicago

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Restrictive cardiomyopathy (RCM) is characterized by noncompliant ventricular walls that resist diastolic filling; one (most commonly the left) or both ventricles may be affected. Symptoms include fatigue and exertional dyspnea. Diagnosis is by echocardiography and cardiac catheterization. Treatment is often unsatisfactory and is best directed at the cause. Surgery is sometimes useful.

Restrictive cardiomyopathy is the least prevalent form of cardiomyopathy. It is classified as

  • Nonobliterative (myocardial infiltration by an abnormal substance)

  • Obliterative (fibrosis of the endocardium and subendocardium)

Either type may be diffuse or nondiffuse (when the disorder affects only one ventricle or part of one ventricle unevenly).

Etiology

Restrictive cardiomyopathy is not always a primary cardiac disorder. Although the cause is usually unknown, it may arise as the consequence of systemic or genetic disorders; identified causes are listed in Causes of Restrictive Cardiomyopathy. Some disorders that cause RCM also affect other tissues (eg, amyloidosis, hemochromatosis). Some myocardial infiltrative disorders also affect other cardiac tissue. Rarely, amyloidosis affects coronary arteries. Sarcoidosis and Fabry disease may also affect nodal conduction tissue. Löffler syndrome (a subcategory of hypereosinophilic syndrome with primary cardiac involvement), which occurs in the tropics, begins as an acute arteritis with eosinophilia, followed by thrombus formation on the endocardium, chordae, and atrioventricular (AV) valves, progressing to fibrosis. Endocardial fibroelastosis (EFE), which occurs in temperate zones, affects only the left ventricle.

Causes of Restrictive Cardiomyopathy

Cause

Examples

Genetic abnormalities

Connective tissue disorders

Endocardial fibroelastosis

Other

Endomyocardial fibrosis (EMF)

Radiation

Pathophysiology

Endocardial thickening or myocardial infiltration (sometimes with death of myocytes, papillary muscle infiltration, compensatory myocardial hypertrophy, and fibrosis) may occur in one, typically the left, or both ventricles. As a result, the mitral or tricuspid valves may malfunction, leading to regurgitation. Functional AV valve regurgitation may result from myocardial infiltration or endocardial thickening. If nodal and conduction tissues are affected, the sinoatrial (SA) and atrioventricular node malfunction, sometimes causing various grades of SA block and AV block.

The main hemodynamic consequence is diastolic dysfunction with a rigid, noncompliant ventricle, impaired diastolic filling, and high filling pressure, leading to pulmonary venous hypertension. Systolic function may deteriorate if compensatory hypertrophy of infiltrated or fibrosed ventricles is inadequate. Mural thrombi can form, resulting in systemic emboli.

Symptoms and Signs

Symptoms are exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, and peripheral edema. Fatigue results from a fixed cardiac output due to resistance to ventricular filling. Atrial and ventricular arrhythmias and AV block are common; angina and syncope are uncommon. Symptoms and signs closely mimic those of constrictive pericarditis.

Physical examination detects a quiet precordium, a low-volume and rapid carotid pulse, pulmonary crackles, and pronounced neck vein distention with a rapid y descent (see Figure: Normal jugular vein waves.). A 3rd and/or 4th heart sound (S3, S4) may occur and must be differentiated from the precordial knock of constrictive pericarditis. In some cases, a murmur of functional mitral or tricuspid regurgitation results because myocardial or endocardial infiltration or fibrosis changes chordae or ventricular geometry. Pulsus paradoxus does not occur.

Diagnosis

  • Echocardiography

  • MRI

  • Left and right heart catheterization

  • Cardiac biopsy

  • Laboratory tests and biopsy of other organ systems as needed

Restrictive cardiomyopathy should be considered in patients with heart failure and preserved ejection fraction, particularly when a systemic disorder known to lead to restrictive cardiomyopathy has already been diagnosed. However, the underlying disorder may not be obvious on presentation.

ECG, chest x-ray, and echocardiography are required.

The ECG is usually nonspecifically abnormal, showing ST-segment and T-wave abnormalities and sometimes low voltage. Pathologic Q waves, not due to previous myocardial infarction, sometimes occur. Left ventricular hypertrophy due to compensatory myocardial hypertrophy or abnormalities of conduction, including AV block, sometimes occurs.

On chest x-ray, the heart size is often normal or small but can be enlarged in late-stage amyloidosis or hemochromatosis.

Echocardiography shows normal left ventricular ejection fraction. Tissue Doppler imaging frequently suggests elevated LV filling pressures, and strain imaging can show impaired longitudinal contraction despite the normal ejection fraction. Other common findings include dilated atria and myocardial hypertrophy. In amyloidosis an unusually bright echo pattern from the myocardium may be observed.

If the diagnosis is still in doubt, MRI can show abnormal myocardial texture in disorders with myocardial infiltration (eg, by amyloid or iron). MRI as well as cardiac CT can detect pericardial thickening, which can help diagnose pericardial constriction which can clinically mimic RCM.

If a definitive diagnosis is not evident after noninvasive testing, invasive work-up with cardiac catheterization and endomyocardial biopsy should be considered. Catheterization detects high atrial pressure in restrictive cardiomyopathy with a prominent y descent and an early diastolic dip followed by a high diastolic plateau in the ventricular pressure curve. Diastolic pressure is usually a few mm Hg higher in the left ventricle than in the right, in contrast to constrictive pericarditis where pressure in the ventricles is equal. Biopsy can detect endocardial fibrosis and thickening, myocardial infiltration by iron or amyloid, chronic myocardial fibrosis, or in the case of Fabry disease, inclusions in vascular endothelial cytoplasm. Coronary angiography is normal, except when amyloidosis affects epicardial coronary arteries.

Laboratory tests and biopsies of other organ systems for the most common causes of RCM (eg, rectal biopsy for amyloidosis, iron tests or liver biopsy for hemochromatosis) should be done.

Prognosis

Prognosis is poor (see Table: Diagnosis and Treatment of Cardiomyopathies) because the diagnosis is often made at a late stage. No treatment is available for most patients; symptomatic, supportive care can be provided. Standard therapies that are used in dilated cardiomyopathy (eg, ACE inhibitors, digoxin, beta-blockers) are poorly tolerated in restrictive disease. These patients may also have autonomic dysfunction (especially in amyloid heart disease) or low systemic blood pressure. There is a high rate of conduction system disease, heart block, and sudden death.

Treatment

  • Cause treated

  • Diuretics considered

Diuretics may be used for patients with edema or pulmonary vascular congestion but must be given cautiously because they can lower preload; the noncompliant ventricles depend on preload to maintain cardiac output. Digoxin does little to alter hemodynamic abnormalities and may cause serious arrhythmias in cardiomyopathy due to amyloidosis, in which extreme digitalis sensitivity is common. If heart rate is elevated, beta-blockers or rate-limiting calcium channel blockers may be used cautiously in low doses. Afterload reducers (eg, nitrates) may cause profound hypotension and usually are not useful.

If the diagnosis is made at an early stage, specific treatment of hemochromatosis, sarcoidosis, and Löffler syndrome may help.

Transplantation is not recommended because the disorder may recur in the transplanted heart.

Key Points

  • In restrictive cardiomyopathy, endocardial thickening or myocardial infiltration leads to a rigid, noncompliant ventricle and thus diastolic dysfunction; systolic function is normal until late in the disease.

  • Sometimes, valvular tissue or the conduction system is involved, causing valvular regurgitation or heart block and arrhythmias.

  • Etiology is usually unknown, but some cases are caused by amyloidosis, hemochromatosis, or sarcoidosis.

  • Diagnosis is by echocardiography plus testing for cause.

  • Treatment is often unsatisfactory unless the cause can be addressed; diuretics may benefit patients with edema or pulmonary vascular congestion but must be used cautiously to avoid lowering preload.

Resources In This Article

* This is the Professional Version. *