ESSENTIALS OF DIAGNOSIS
Right heart failure tends to dominate over left heart failure.
Pulmonary hypertension is present.
Amyloidosis is the most common cause.
Echocardiography is key to diagnosis.
Radionuclide imaging or myocardial biopsy can confirm amyloid.
Restrictive cardiomyopathy is characterized by impaired diastolic filling with reasonably preserved contractile function (VIDEO 10–25). The condition is relatively uncommon, with the most frequent cause being amyloidosis. Cardiac amyloidosis is more common in men than in women and rarely manifests before the age of 40. While light-chain amyloid proteins can be toxic to cardiomyocytes, they may also internalize into many cell types and this may explain some of the cardiac dysfunction observed. The AL (light-chain) type is the most common, with cardiac involvement in 50%. Other forms include mutated transthyretin (ATTR) in familial amyloidosis (usually manifested in the elderly black population) and a wild-type transthyretin amyloidosis. Transthyretin is produced almost entirely in the liver. Secondary (AA) amyloidosis due to fragments of serum amyloid A protein associated with chronic inflammatory disorders is a rare cause of cardiac disease. An isolated atrial amyloid form is also recognized.
Video 10–25: Restrictive cardiomyopathy on pulse wave doppler examination.
(Used, with permission, from B Macrum and E Foster.)
The differential diagnosis of a restrictive cardiomyopathy includes infiltrative disorders beside amyloidosis, such as sarcoidosis, Gaucher disease, and Hurler syndrome. Storage diseases such as hemochromatosis, Fabry disease, and glycogen storage diseases can also produce the picture. Noninfiltrative diseases, such as familial cardiomyopathy and pseudoxanthoma elasticum, can be implicated rarely, and other secondary causes include diabetes, scleroderma, radiation, chemotherapy, CAD, and longstanding hypertension.
Concentric LVH usually results in an increase in the LVEF via the law of Laplace where wall thickness is inversely proportional to wall tension. In restrictive cardiomyopathy the walls are thickened, but the LVEF is lower; this is often a clue to the presence of an infiltrative process.
Restrictive cardiomyopathy must be distinguished from constrictive pericarditis (see Table 10–17). The key feature is that ventricular interaction is accentuated with respiration in constrictive pericarditis and that interaction is absent in restrictive cardiomyopathy. In addition, the pulmonary arterial pressure is invariably elevated in restrictive cardiomyopathy due to the high PCWP and is normal in uncomplicated constrictive pericarditis. Symptoms may include angina, syncope, stroke, and peripheral neuropathy. Periorbital purpura, a thickened tongue, or hepatomegaly are all suggestive physical findings of amyloidosis.
Conduction disturbances are frequently present. Low voltage on the ECG combined with ventricular hypertrophy on the echocardiogram is suggestive of disease. Technetium pyrophosphate imaging (bone scan imaging) can also identify amyloid deposition in the myocardium, and it has become the noninvasive imaging modality of choice for diagnosing transthyretin amyloidosis. With typical ...