Restrictive Cardiomyopathy

General Principles

Restrictive cardiomyopathy (RCM) is characterized by a rigid heart with poor ventricular filling but generally a nondilated LV and normal LVEF. Right HF symptoms often predominate.
RCM may be primary, including conditions such as idiopathic RCM, endomyocardial fibrosis, and Löeffler endocarditis, or secondary to either infiltrative conditions (amyloidosis, sarcoidosis, hypereosinophilic syndrome) or storage diseases (Fabry disease, hemochromatosis, and the glycogen storage diseases).
Constrictive pericarditis may present similarly to RCM but is a disease wherein the pericardium limits diastolic filling. Constriction carries a different prognosis and therapy, and the distinction between constriction and RCM is essential.

In amyloidosis, misfolded protein (amyloid) deposits in the cardiac interstitium, interrupting the normal myocardial contractile units and causing restriction. Most commonly, the misfolded protein is either AL or TTR.
In sarcoidosis, granulomatous infiltration of the myocardium is often subclinical and more commonly presents with arrhythmias or conduction system disease; however, in up to 5% of sarcoidosis cases, restriction occurs.
In hemochromatosis, excess iron is deposited in the cardiomyocyte sarcoplasm, ultimately overcoming antioxidant capacity and resulting in lipid peroxidation and membrane permeability. Injury occurs initially in the epicardium and then later in the myocardium and endocardium, with systolic function initially preserved.
Fabry disease, an X-linked genetic disorder, is characterized by deficient activity of the lysosomal enzyme α-galactosidase A, resulting in lysosomal accumulation of globotriaosylceramide in tissues. More than half of patients develop cardiomyopathy, typically with LV hypertrophy and RCM.

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