Restrictive cardiomyopathies are characterized by a non-dilated ventricle, normal wall thickness, and usually preserved left ventricular systolic function parameters (ejection fraction). However, due to rigid ventricular walls, diastolic dysfunction and elevated filling pressures develop, resulting in atrial dilatation, venous congestion, and the inability to increase stroke volume, fig. A.
The physiology of restrictive ventricular filling is not specific. Differentiation between restrictive cardiomyopathy, i. e. filling disturbance due to muscular dysfunction, and constrictive pericarditis may be challenging, yet it is of utmost importance since the latter disorder may be treated surgically. A careful echocardiographic and hemodynamic assessment including pericardial imaging and sometimes endomyocardial biopsy is thus important.
Idiopathic or primary restrictive cardiomyopathy is a diagnosis of exclusion since a restrictive physiology as outlined above may be seen in several other cardiac and systemic disorders:
- advanced stages of other cardiomyopathies (- i. e. dilated or hypertrophic cardiomyopathy), hypertensive or ischemic heart disease,
- infiltrative disorders like amyloidosis, sarcoidosis, Gaucher disease, Hurler syndrome, and fatty infiltration
- storage disorders like hemochromatosis, Fabry disease, and glycogen storage disease
- other disorders like endomyocardial fibrosis, radiation, chemotherapy, hypereosinophilic syndrome, carcinoid heart disease,
metastatic cancers, and drugs
Familial restrictive cardiomyopathy is extremely rare. Genetic studies suggest that there may be an overlap concerning the phenotypic expression of RCM with familial hypertrophic cardiomyopathy (HCM).
Idiopathic restrictive cardiomyopathy can be observed at any age. However, it is increasing in the elderly and more common in female. Typical symptoms are dyspnea, peripheral edema, palpitations, fatigue, weakness, and exercise intolerance due to an impaired cardiac output (impaired ventricular filling).
- Physical examination: A low stroke volume might lead to tachycardia and low pulse amplitude, elevated jugular venous pressures are usually seen. Sometimes an inspiratory increase in venous pressure can be observed (Kussmaul´s sign).
- Auscultation: Heart sounds are oftentimes normal. Due to the rapid ventricular filling, a third heart sound (S3) may be audible as well as regurgitation murmers of the AV valves.
- Electrocardiogram: ECG changes are nonspecific. In contrast to constrictive pericarditis or amyloidosis QRS voltage is usually normal. Some patients develop atrial fibrillation or conduction abnormalities like atrioventricular block or intraventricular conduction delays.
- Chest x-ray: Atrial enlargement, signs of pulmonary venous congestion or pleural effusion may be present. Pericardial calcifications should be actively searched for since they are typical for constrictive pericarditis.
- Plasma BNP: Plasma concentrations of brain natriuretic peptide (BNP) are increased in RCM. Due to the higher wall stress in restrictive cardiomyopathy than in constrictive pericarditis, BNP plasma levels might be higher in restrictive cardiomyopathy.
- Echocardiography: Echocardiography demonstrates the typical but non-specific morphologic constellation of a non-hypertrophied, non-dilated ventricle with preserved systolic function and dilated atria (fig. B). In addition, Doppler techniques allow for assessment of the restrictive filling dynamics of the left and of the right ventricle (- correlates of a “dip-plateau”-pressure-curve, fig. A). The restrictive filling pattern of the trans-mitral flow profile is characterized by a rapid (<140 ms) deceleration of the E-wave and an E/A-ratio > 2.0 (fig. C). By acute preload reduction (e. g. a Valsalva manoeuvre) it can be verified whether the restrictive filling pattern is reversible or fixed (fig. A). A fixed restrictive trans-mitral flow profile is associated with an unfavourable prognosis, independently from the underlying disease. Tissue Doppler imaging (TDI) is helpful not only for grading diastolic dysfunction but also for the differentiation between restrictive cardiomyopathy and pericardial constriction, fig. D: while restriction is characterized by reduced velocities of the mitral annular plane (arrow: 5 cm/s), this measure is normal (>8-10 cm/s) in constriction. Accompanying valve regurgitations may also be assessed by echocardiography.
- Cardiac MRI: Like echocardiography cardiac MRI is able to demonstrate the morphologic constellation of RCM. However, specific MRI techniques allow for a more detailed characterization of the myocardial wall composition, i. e the detection of myocardial edema, fibrosis, or some specific substrates (e. g. iron). In cardiac amyloidosis oftentimes pericardial- and pleural effusions can be detected. Almost pathognomonic for this disorder is an uncommon inhomogeneous enhancement of contrast agent in the myocardium with a rapid loss of contrast in the ventricular cavity.  Direct visualization of the pericardium is rather possible by MRI than by echocardiography. However, pronounced calcifications of the pericardium are easier to capture by computed tomography (CT).
- Endomyocardial biopsy: In order to exclude specific heart muscle diseases and myocarditis endomyocardial biopsy can be performed. The procedure is highly specific for excluding specific heart muscle disorders.
There are specific treatments for some underlying diseases of secondary restrictive physiology like in sarcoidosis or hemochromatosis. However, there is no specific treatment for idiopathic restrictive cardiomyopathy.
In order to increase ventricular filling heart, rate control is an important therapeutic goal. Both tachy- and bradycardia may pose problems. Calcium channel blockers (eg, verapamil) and also beta blockers may increase filling time. On the other hand, pronounced bradycardia may require pacemaker implantation. The maintenance of atrial contraction is another therapeutic goal.
Angiotensin-converting enzyme (ACE) inhibitors and/or angiotensin II receptor blockers have proven benefits for patients with systolic heart failure. Their role for the treatment of diastolic heart failure remains unclear yet. Probably myocardial stiffness is positively being influenced by a reduction of myocardial angiotensin II production. Diuretics are used to counteract systemic and pulmonary venous congestion. However, therapy should be closely monitored because patients with restrictive cardiomyopathy need higher filling pressures to maintain cardiac output. However, patients with atrial fibrillation should be treated by anticoagulants in order to avoid thromboembolism.
In eligible patients with severe heart failure heart transplantation or treatment by ventricular assist device systems may be necessary.
Despite optimal medical treatment, prognosis of patients with severe diastolic dysfunction remains poor. Adverse factors seem to be male gender, higher age, increment in NYHA functional class, and left atrial diameter.
Idiopathic or primary restrictive cardiomyopathy is a rare disease and a diagnosis of exclusion. Patients suffer from pulmonary and systemic congestion and reduced stroke volume. Although this may be challenging, current diagnostic techniques usually allow for differentiating idiopathic restrictive cardiomyopathy from constrictive pericarditis and secondary forms of restriction. There is no specific therapy for idiopathic restrictive cardiomyopathy, whereas patients with secondary forms may benefit from therapy of the underlying disease (e.g. sarcoidosis, hemochromatosis). Despite optimal therapy prognosis of affected patients is poor.
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- ↑ Friedrich SP, Lorell BH, Rousseau MF, et al. Intracardiac angiotensin-converting enzyme inhibition improves diastolic function in patients with left ventricular hypertrophy due to aortic stenosis. Circulation 1994; 90:2761.