Endomyocardial Fibrosis: Tropical Cardiomyopathy

Endomyocardial fibrosis (EMF) is a restrictive cardiomyopathy characterized by progressive fibrosis of the endocardium and subendocardial myocardium, primarily affecting the ventricular apices and inflow tracts. EMF is the most common restrictive cardiomyopathy worldwide, predominantly found in tropical and subtropical regions of Africa, South America, and South/Southeast Asia. The disease progresses through three pathological phases: (1) Active/necrotic phase: acute inflammation with eosinophilic myocarditis (some cases show marked eosinophilia similar to Loeffler endocarditis), myocardial necrosis, and arteritis; eosinophil degranulation releases major basic protein (MBP) and eosinophilic cationic protein (ECP), which are directly toxic to endocardial cells and promote thrombus formation. (2) Thrombotic phase: mural thrombi form over the damaged endocardium, particularly at the ventricular apices; these thrombi organize and contribute to the fibrotic process. (3) Fibrotic phase (chronic, dominant phase): dense fibrosis replaces the endocardium and subendocardium with collagen up to several millimeters thick, creating a rigid, non-compliant ventricular chamber that severely restricts diastolic filling (restrictive physiology). The fibrosis characteristically involves the ventricular apices (causing 'obliteration' of the apex), extends to involve the chordae tendineae and papillary muscles (causing mitral and/or tricuspid...