Definition of Restrictive Cardiomyopathy
Classification of the cardiomyopathies in general, and restrictive cardiomyopathy in specific, has been controversial. A recent American Heart Association consensus document proposed that cardiomyopathies be classified as either primary (ie, predominantly confined to the heart) or secondary (ie, as part of a generalized systemic disorder).1 A working group of the European Society of Cardiology proposed a classification scheme based on ventricular morphology and function and the familial/genetic backround.2 These proposals offer an alternative to an earlier report from the 1995 World Health Organization/International Society and Federation of Cardiology (WHO/IFSFC) Task Force, which classified cardiomyopathies by dominant pathophysiology or, whenever possible, by etiologic and pathogenetic factors. However, there are several limitations with the earlier approach: (1) the clinical expression of the various cardiomyopathies demonstrates considerable overlap (eg, hypertrophic, infiltrative, and storage diseases are characterized by increased wall thickness and absence of dilation); (2) the anatomic and pathophysiologic expressions of the cardiomyopathies are not static because of cardiac remodeling and the vicissitudes of natural history (eg, amyloidosis and hypertrophic cardiomyopathy can progress from a nondilated to a dilated left ventricular [LV] with systolic dysfunction); (3) the confusion and apparent contradictions that result from a failure to account for recent genetic insights into etiology (eg, restrictive cardiomyopathy may be caused by mutations in sarcomeric genes that have been associated with hypertrophic, dilated, and noncompaction cardiomyopathy) and pathophysiology (eg, some individuals carrying a disease-causing gene mutation fail to express a phenotype or express only a subtle clinical manifestation);3 and, (4) the ambiguities that exist when attempting to categorize heterogeneous disorders by etiology (eg, a myopathic phenotype can have toxic, metabolic, ischemic, or genetic origins).1 Accordingly, it has been suggested that the taxonomy of the cardiomyopathies be reclassified to account for the molecular phenotype using genomic and genetic approaches.4
Restrictive cardiomyopathy refers to either an idiopathic or a systemic myocardial disorder (in the absence of ischemic, hypertensive, valvular, and congenital heart disease) characterized by restrictive filling, normal or reduced LV and right ventricular (RV) volumes, and normal or nearly normal systolic (LV and RV) function. Except for primary nonhypertrophic cardiomyopathy and a few infiltrative diseases (see below), restrictive cardiomyopathies are secondary. These can be noninfiltrative or infiltrative and occur with or without obliteration; infiltration can be interstitial (eg, amyloidosis, sarcoidosis) or cellular (eg, hemochromatosis).
Clinical Features of Restrictive Cardiomyopathy
Involvement of the myocardium (or endomyocardium) and ventricular obliteration can occur either in isolation or in the setting of systemic or iatrogenic disease (Table 34–1). Irrespective of the etiology, terminology, or nature of the myocardial process, the ventricles are small (generally <110 mL/m2), and stiff, restricting ventricular filling. Despite normal (or near normal) systolic function at rest, ventricular diastolic, jugular, and pulmonary venous pressures are increased. Elevated atrial pressures produce symptoms of systemic and pulmonary venous congestion (dyspnea, orthopnea, edema, abdominal discomfort), and underfilled ventricles result in reduced ...