Restrictive Cardiomyopathy

Of the three major functional categories of cardiomyopathies (dilated, hypertrophic, and restrictive), the restrictive cardiomyopathies (RCMs) are the least common in the Western world, but unfortunately often are associated with the greatest morbidity and mortality. Infiltrative disease of the myocardium (often caused by amyloidosis) is a common cause of RCMs and has a significantly lower long-term survival rate when compared to cardiomyopathies of various other causes. Treatment of the RCM is, in general, difficult and often ineffective. Because of the abnormalities of diastolic filling that are characteristic of this condition, general measures to reduce venous and systemic congestion such as with the use of diuretics, are desirable but often result in an attendant reduction in stroke volume and cardiac output. Digoxin, calcium channel blocking drugs, and beta-adrenergic blocking agents are of limited value, although they may be used with benefit to control the heart rate response in the subgroup of patients with atrial fibrillation. Angiotensin-converting enzyme inhibitors are generally ineffective in RCM. Targeted therapy directed against specific causal entities (such as the use of somatostatin analogues in carcinoid syndrome or iron chelation with desferrioxamine in hemochromatosis) may be more effective than simple symptomatic therapy. Differentiation of RCM from constrictive pericarditis is crucial, since constriction may be treated effectively by surgical removal of the thickened pericardium. A limited number of patients appear to have benefited from novel treatment strategies, such as autologous stem cell transplant in amyloidosis, balloon valvuloplasty of stenotic tricuspid or pulmonary valves in cardiac carcinoid syndrome, and cardiac transplantation. Truly effective therapy for RCM is generally lacking, and the best chance for optimizing the clinical outcome is early detection and aggressive medical treatment in an attempt to maintain the highest possible level of patient function for as long as possible.