Restrictive cardiomyopathy is the least common form of cardiomyopathy. This condition gets its name from the way it restricts the heart from stretching properly.
While the rhythm and pumping action of the heart may be healthy, the stiff walls of the heart chambers keep them from filling normally.
So blood flow is reduced, and blood that would normally enter the heart is backed up in the circulatory system. In time, the heart fails.
What causes it?
Restrictive cardiomyopathy is often caused by diseases in other parts of the body.
One known cause is cardiac amyloidosis, which is sometimes associated with cancers of the blood.
Amyloidosis is a condition that causes proteins from certain blood cells (called amyloid deposits) to build up in the heart tissue, making the tissue stiff and thickened. Cardiac amyloidosis is also called “stiff heart syndrome.”
Another known cause is a disorder called hemochromatosis. This disorder is passed down through family members and results in a buildup of iron in the body.
Sarcoidosis is the name of an inflammatory disease that starts as tiny, grain-like lumps called granulomas, which most often appear in your lungs or lymph nodes.
The granulomas can clump together and form larger lumps that attack other organs. Sarcoidosis often affects your skin, eyes, or liver, but it can also cause restrictive cardiomyopathy.
In other cases, diseases create deposits that can make the heart walls thick and stiff.
Another term for restrictive cardiomyopathy is infiltrative cardiomyopathy, because it is the “infiltration” of different materials, such as the amyloids or the granulomas, in the heart that lead to the cardiomyopathy.
Restrictive cardiomyopathy can also result from scarring of the heart, caused by a heart attack.
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 node malfunctions, sometimes causing various grades of AV block.
The main hemodynamic consequence is diastolic dysfunction (see Heart Failure: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, and, when the right ventricle is affected, 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.
A 4th heart sound (S 4 ) is almost always present; a 3rd heart sound (S 3 ) 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.
- Testing for cause
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 MI, sometimes occur.
Left ventricular hypertrophy due to compensatory myocardial hypertrophy 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 systolic function. Common findings include dilated atria and myocardial hypertrophy.
RCM due to amyloidosis has an unusually bright echo pattern from the myocardium. Echocardiography helps differentiate constrictive pericarditis with its thickened pericardium, but paradoxical septal motion can occur in either disorder.
If the diagnosis is still in doubt, CT may be more sensitive in showing whether the pericardium is normal, and MRI can show abnormal myocardial texture in disorders with myocardial infiltration (eg, by amyloid or iron).
Cardiac catheterization and myocardial biopsy are not often necessary. If done, catheterization detects high atrial pressure in RCM, with a prominent y descent and an early diastolic dip followed by a high diastolic plateau in the ventricular pressure curve.
In contrast to constrictive pericarditis findings, diastolic pressure is usually a few mm Hg higher in the left ventricle than in the right.
Angiography detects normal-sized ventricular cavities with normal or decreased systolic shortening.
AV valve regurgitation may be present. Biopsy can detect endocardial fibrosis and thickening, myocardial infiltration by iron or amyloid, and chronic myocardial fibrosis. Coronary angiography is normal, except when amyloidosis affects epicardial coronary arteries. Occasionally, cardiac catheterization is not diagnostic, and rarely, thoracotomy is required to explore the pericardium.
Tests for the most common causes of RCM (eg, rectal biopsy for amyloidosis, iron tests or liver biopsy for hemochromatosis) should be done.
How is it diagnosed?
Restrictive cardiomyopathy can be mistaken for a condition called constrictive pericarditis. This condition causes the sac-like membrane around the heart (the pericardium) to become inflamed and thickened.
Surgery can usually correct constrictive pericarditis.
On the other hand, restrictive cardiomyopathy cannot be corrected surgically. Instead, doctors will try to control its symptoms.
Diagnostic tools include the following:
Echocardiography can be used to show the size of your heart and how much muscle damage there is.
Computed tomography (CT) scanning gives slice-like pictures of your heart that can be used to show how the heart is working.
Magnetic resonance imaging (MRI) can give detailed pictures of the heart and its various structures.
A biopsy of tissue from the wall of your heart may help doctors find out how seriously your heart has been damaged, or what process may be causing the damage.
Cardiac catheterization can show movement and force of blood through the heart (called hemodynamic analysis).
How is it treated?
Doctors may be able to treat the condition that is causing restrictive cardiomyopathy, but the heart problem itself generally cannot be reversed.
Doctors currently have no way of repairing severely damaged heart muscle. So the treatment goal is mainly controlling the symptoms of restrictive cardiomyopathy.
Medicines are sometimes used to ease the heart’s workload and to keep a regular heart rhythm. When the condition becomes severe, a heart transplant may be needed.
Prognosis is poor (see 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.