Infiltrative Cardiomyopathy

Infiltrative cardiomyopathy describes myocardial injury caused by material deposited within the heart or by inflammatory cells that later leave scar. The result is not one uniform disease. Cardiac amyloidosis mainly produces a stiff, thick-walled ventricle; cardiac sarcoidosis produces inflammation, scar, and electrical instability; iron overload can progress from diastolic dysfunction to a dilated, systolically failing heart. In cardiac amyloidosis, misfolded protein fibrils accumulate in the extracellular space. The two clinically dominant forms are AL amyloidosis, produced by a clonal plasma-cell disorder, and ATTR amyloidosis, produced by unstable transthyretin that is either wild-type or caused by a hereditary TTR variant. The deposits separate and encase cardiomyocytes, so the ventricular wall may become thick without a proportional increase in muscle mass. This is pseudo-hypertrophy. A stiff ventricle cannot relax and fill normally. Filling pressures rise, the atria enlarge, and the patient commonly develops heart failure with preserved or mildly reduced ejection fraction. Stroke volume becomes relatively fixed: the heart has little ability to increase output when the patient stands, exercises, or becomes tachycardic. Autonomic neuropathy can add vasodilation and orthostatic hypotension. These...