Localization of lesions in endomyocardial fibrosis.

The lesions in tropical endemic endomyocardial fibrosis have a characteristic localization at the ventricular apex and on the mural endocardium behind the posterior cusp of the mitral valve. There is often a conspicuous ridge on the septal wall of the left ventricle. The use of a model left ventricle provides a possible explanation for the localization and character of the lesions in endomyocardial fibrosis. A study of ventricular diastolic flow patterns shows that the incoming jet strikes the left ventricular apex and spreads around the sides of the ventricle to produce a strong asymmetrical ring vortex. The main vortex strength and the highest wall shear stress is in the outflow tract and behind the anterior cusp. The region behind the posterior cusp is almost stagnant during diastole and the wall shear stress is very low. In systole, wall shear stress is high only in the outflow tract. The distribution ofendomyocardialfibrosis appears to be confined initially to regions of low wall shear stress.