Endomyocardial Fibrosis

Endomyocardial fibrosis is characterized by progressive fibrosis and thickening of the ventricular endocardium that result in restrictive cardiomyopathy. The prevalence of this disease is greater in tropical and subtropical countries where parasitosis is frequently encountered. Endomyocardial fibrosis can also be encountered in temperate countries and is then associated with hypereosinophilia as part of Löffler's syndrome.

The disease process involves the left (30%), the right (10%), or both ventricles (60%). A thick fibrotic layer with scattered thrombi severely adherent to the ventricular endocardium typically begins at the apical level and then extends towards the outflow tracts and atrioventricular valves, involving first the papillary muscles and chordae and later the leaflets and annulus. The two most common consequences of this disease process are ventricular obliteration with restrictive diastolic filling and atrioventricular valve dysfunction.

The clinical picture is that of the absence of diastole, with progressively severe symptoms of pulmonary edema, peripheral edema, and hepatomegaly. Either mitral or tricuspid regurgitation, or both, is frequently present at a later stage.

On echocardiography, the most striking anomaly is the huge dilatation of the left or right atrium, or both atria, and the most characteristic finding is the apical obliteration and endocardial thickening of the ventricles. The most common mechanism of atrioventricular valve regurgitation is diastolic restricted leaflet motion (type IIIa). The posterior leaflet of the mitral valve or the septal leaflet of the tricuspid valve is commonly thickened and incorporated in the fibrotic process. Subvalvular involvement with chordae fusion and thickening and papillary muscle fibrosis may also be present. Occasionally anterior leaflet prolapse (type II) resulting from chordae elongation can also be observed. Finally, significant annular dilatation is a common secondary lesion in these patients.

Cardiac catheterization shows a restrictive diastolic filling pattern with a dip-plateau recording aspect in the right atrium, right ventricle, and pulmonary artery in patients with extensive right-sided disease. In patients with left-side involvement, elevated left ventricular end-diastolic pressure and pulmonary hypertension are common findings. Left ventricular angiography commonly shows an apical defect.

On magnetic resonance imaging, endomyocardial fibrosis is characterized by diffuse and intense hyperenhancement of the ventricular endocardium.

Histological findings show significant fibrotic thickening of the ventricular endocardium with infiltration of fibrous tissue in the underlying myocardium. During the evolution of the disease, calcification of the fibrotic process is a common observation. In addition, thrombus formation covering the surface of the fibrotic layer may be observed.