A cardiomyopathy is a primary disorder of the heart muscle (see also Overview of Cardiomyopathies Overview of Cardiomyopathies A cardiomyopathy is a primary disorder of the heart muscle. It is distinct from structural cardiac disorders such as coronary artery disease, valvular disorders, and congenital heart disorders... read more ).
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 of Restrictive Cardiomyopathy
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 the table Causes of Restrictive Cardiomyopathy Causes of Restrictive Cardiomyopathy . Some disorders that cause restrictive cardiomyopathy also affect other tissues (eg, amyloidosis Amyloidosis Amyloidosis is any of a group of disparate conditions characterized by extracellular deposition of insoluble fibrils composed of misaggregated proteins. These proteins may accumulate locally... read more , hemochromatosis Hereditary Hemochromatosis Hereditary hemochromatosis is a genetic disorder characterized by excessive iron (Fe) accumulation that results in tissue damage. Manifestations can include systemic symptoms, liver disorders... read more ). Some myocardial infiltrative disorders also affect other cardiac tissue. Rarely, amyloidosis Amyloidosis Amyloidosis is any of a group of disparate conditions characterized by extracellular deposition of insoluble fibrils composed of misaggregated proteins. These proteins may accumulate locally... read more affects coronary arteries. Sarcoidosis Sarcoidosis Sarcoidosis is an inflammatory disorder resulting in noncaseating granulomas in one or more organs and tissues; etiology is unknown. The lungs and lymphatic system are most often affected, but... read more and Fabry disease Fabry Disease Fabry disease is a sphingolipidosis, an inherited disorder of metabolism, caused by deficiency of alpha-galactosidase A, which causes angiokeratomas, acroparesthesias, corneal opacities, recurrent... read more may also affect nodal conduction tissue. Löffler syndrome Löffler Syndrome Löffler syndrome is a form of eosinophilic pulmonary disease characterized by absent or mild respiratory symptoms (most often dry cough), fleeting migratory pulmonary opacities, and peripheral... read more (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 infants and children, affects only the left ventricle. Endomyocardial fibrosis (EMF) occurs commonly in tropical regions and affects both the left and right ventricles.
Pathophysiology of Restrictive Cardiomyopathy
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 Sinus Node Dysfunction Sinus node dysfunction refers to a number of conditions causing physiologically inappropriate atrial rates. Symptoms may be minimal or include weakness, effort intolerance, palpitations, and... read more and AV block Atrioventricular Block Atrioventricular (AV) block is partial or complete interruption of impulse transmission from the atria to the ventricles. The most common cause is idiopathic fibrosis and sclerosis of the conduction... read more .
The main hemodynamic consequence is diastolic dysfunction Heart failure with preserved ejection fraction (HFpEF) 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 of Restrictive Cardiomyopathy
Symptoms of restrictive cardiomyopathy 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 Constrictive pericarditis Pericarditis is inflammation of the pericardium, often with fluid accumulation in the pericardial space. Pericarditis may be caused by many disorders (eg, infection, myocardial infarction, trauma... read more .
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 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 of Restrictive Cardiomyopathy
Sometimes left and right heart catheterization, including 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 Electrocardiography The standard electrocardiogram (ECG) provides 12 different vector views of the heart’s electrical activity as reflected by electrical potential differences between positive and negative electrodes... read more 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 Echocardiography This photo shows a patient having echocardiography. This image shows all 4 cardiac chambers and the tricupsid and mitral valves. Echocardiography uses ultrasound waves to produce an image of... read more 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. Technetium-99m pyrophosphate cardiac imaging is also useful in differentiating immunoglobulin light chain (AL) from transthyretin (ATTR) cardiac amyloid. Strongly positive scans are specific for ATTR amyloid. Weakly positive scans may occur with AL amyloid, recent myocardial infarction, or significant chronic kidney disease. Because scan results are not always specific, AL amyloid should be ruled out using serum light chain and urine/serum immunofixation studies. Identifying the type of amyloid has implications for treatment, genetic counseling, and overall prognosis ( 1 Diagnosis reference Restrictive cardiomyopathy is characterized by noncompliant ventricular walls that resist diastolic filling; one (most commonly the left) or both ventricles may be affected. Symptoms include... read more ).
If the diagnosis is still in doubt, MRI MRI Cardiac imaging tests can delineate cardiac structure and function. Standard imaging tests include Echocardiography Chest x-ray CT MRI read more 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 restrictive cardiomyopathy.
Cardiac CT-positron emission tomography assessment may be useful in patients with sarcoidosis that affects the heart because cardiac sarcoidosis may manifest similarly to other causes of restrictive cardiomyopathy.
If a definitive diagnosis is not evident after noninvasive testing, invasive work-up with cardiac catheterization Cardiac Catheterization Cardiac catheterization is the passage of a catheter through peripheral arteries or veins into cardiac chambers, the pulmonary artery, and coronary arteries and veins. Cardiac catheterization... read more 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 restrictive cardiomyopathy (eg, fat pad biopsy for amyloidosis, iron tests or liver biopsy for hemochromatosis) should be done.
1. Bokhari S, Castaño A, Pozniakoff T, et al: (99m)Tc-pyrophosphate scintigraphy for differentiating light-chain cardiac amyloidosis from the transthyretin-related familial and senile cardiac amyloidoses. Circ Cardiovasc Imaging 6:195–201, 2013.
Prognosis for Restrictive Cardiomyopathy
Prognosis is poor (see table Diagnosis and Treatment of Cardiomyopathies 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, angiotensin-converting enzyme [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 of Restrictive Cardiomyopathy
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 some forms of amyloidosis Amyloidosis Amyloidosis is any of a group of disparate conditions characterized by extracellular deposition of insoluble fibrils composed of misaggregated proteins. These proteins may accumulate locally... read more , hemochromatosis Treatment Hereditary hemochromatosis is a genetic disorder characterized by excessive iron (Fe) accumulation that results in tissue damage. Manifestations can include systemic symptoms, liver disorders... read more , sarcoidosis Sarcoidosis Sarcoidosis is an inflammatory disorder resulting in noncaseating granulomas in one or more organs and tissues; etiology is unknown. The lungs and lymphatic system are most often affected, but... read more , and Löffler syndrome Löffler Syndrome Löffler syndrome is a form of eosinophilic pulmonary disease characterized by absent or mild respiratory symptoms (most often dry cough), fleeting migratory pulmonary opacities, and peripheral... read more may help.
Left ventricular assist device (LVAD) and transplantation are sometimes recommended ( 1 Treatment reference Restrictive cardiomyopathy is characterized by noncompliant ventricular walls that resist diastolic filling; one (most commonly the left) or both ventricles may be affected. Symptoms include... read more ).
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.
Standard treatments for dilated cardiomyopathy (eg, ACE inhibitors, digoxin, beta-blockers) are poorly tolerated in restrictive disease.
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