Restrictive Cardiomyopathy



Restrictive cardiomyopathies are less common than the dilated and hypertrophic varieties. They are caused by a variety of infiltrative processes, including amyloidosis, hemochromatosis, sarcoi­dosis, endomyocardial fibrosis, Lofflers’ endocar­ditis, and Fabry’s disease. Restrictive cardiomy­opathy is characterized by abnormal diastolic function that impedes ventricular filling. Con­tractile function is usually relatively normal. Re­strictive cardiomyopathy is often difficult to dis­tinguish from constrictive pericarditis, and endomyocardial biopsy may sometimes be nec­essary to make the distinction. Ventricular pres­sure recordings reveal a deep nadir in early dias­tole with a rapid rise to a plateau, termed the “square root” sign. The atrial pressure tracing demonstrates a corresponding prominent “y” de­scent with a rapid rise and plateau. The “x” de­scent and “a” wave are also often prominent, re­sulting in a characteristic M-shaped waveform. The left-sided filling pressures are often higher than the right-sided pressures, in distinction to the equalization of pressures in constrictive per­icarditis.

Signs and symptoms are listed in Table 9-1. Kussmaul’s sign (an inspiratory increase in cen­tral venous pressure) may be present. The apical impulse is usually palpable, in distinction to con­strictive pericarditis.

Amyloidosis is characterized by deposition in many tissues of an amorphous, hyaline-like sub­stance and is the most common cause of restric­tive cardiomyopathy. In addition, it sometimes may cause systolic dysfunction and symptoms more typical of a dilated cardiomyopathy. Ar­rhythmias and conduction disturbances are com­mon. The electrocardiogram in cardiac amyloi­dosis is usually abnormal and often demonstrates generalized decreased voltage. Q waves from my­ocardial infiltration may simulate myocardial in­farction. Echocardiography reveals increased thickness of all cardiac structures, including the ventricular walls, the atrial septum, and the car­diac valves. A characteristic sparkling texture of the myocardium is typical on echocardiography. Diagnosis is made by biopsy of various tissues; if necessary, endomyocardial left or right ventric­ular biopsies may be performed. There is no treat­ment for the cardiac manifestations of amyloi­dosis, and the disease is slowly progressive. Digoxin must be used with caution because pa­tients are particularly sensitive to its toxic effects.

Pacemaker implantation may be necessary in pa­tients who develop atrioventricular block. Death from congestive heart failure as well as sudden death, presumably due to arrhythmias, occurs.