The main microscopic feature of endomyocardial fibrosis (as well as of Loeffler’s disease) is fibrosis of the inner lining of the heart cavities (the endocardium). This means that the normal endocardium is replaced by a thick, inelastic tissue. The fibrotic lesions may be over 1 cm thick and may extend finger-like projections into the heart muscle (the myocardium).
Fibrosis frequently affects the heart asymmetrically. It may specifically involve one or more of the following areas: the top (apex) of the left ventricle, the back (posterior) wall of the left ventricle including the fibrous cords that connect the valves to the ventricles (the chordae tendineae), and the top (apex) of the right ventricle, extending backwards to encase the muscle and cords (chordae tendineae) attaching the heart valve (tricuspid).
If fibrosis of the left ventricle is predominant, then blood flow from the right side of the heart is reduced often with mitral valve failure causing back-flow (regurgitation) of blood. The results may include pulmonary venous hypertension and left ventricular enlargement. Abnormal heartbeat patterns (atrial fibrillation or atrial arrhythmia) are common. Difficulty in breathing (dyspnea) especially, but not exclusively, on physical exertion is the major physical sign.
If fibrosis of the right ventricle is predominant, then circulation is restricted often with tricuspid valve failure, causing backflow (tricuspid regurgitation). Enlargement of the heart (cardiomyopathy) because of right atrial dilatation is often seen. Facial Swelling (edema), Swelling of the legs, enlargement of the spleen and liver (hepatosplenomegaly), and an accumulation of fluid in the abdominal cavity (ascites) are to be expected.
Biventricular fibrosis with circulation features is a mixture of the two forms listed above. That is, the symptoms are a combination of left and right ventricular fibrosis.
The extracardiac manifestations of Loeffler’s disease include emboli to the brain (stroke), spotty (petechial) hemorrhages, and an enlarged liver (hepatomegaly).