NORD gratefully acknowledges Lori A Blauwet, MD, Associate Professor of Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, for assistance in the preparation of this report.
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).
At this time, clinicians believe that an as yet unknown immunological process is the preferred explanation for the cause of most cases of endomyocardial fibrosis and Loeffler’s disease. In the past, the cause of both conditions was attributed to the presence of the filaria worm in patients or to poor nutrition. Widespread infection with such worms and poor diets are typical in the tropical regions in which these disorders are more common. Eosinophils have been observed in some cases of endomyocardial fibrosis, suggesting a form of hypersensitivity may play a role in select cases. In children, endomyocardial fibrosis has been associated with the mumps virus.
Endomyocardial fibrosis is principally an endemic disease of the equatorial tropics. It is exceedingly rare in Europe and North America. It affects all races, mostly children and young adults. The disease has been described in a few patients over 60 years of age and, rarely, in patients younger than 5 years of age.
Echocardiography is the primary tool used to diagnose suspected cases of endomyocardial fibrosis or Loeffler’s disease. A heart muscle biopsy is sometimes obtained to confirm the diagnosis.
Responses to medical treatment are generally poor and unproven. For patients with severe symptoms, surgical treatment may be pursued when other treatments have not been successful. These procedures, however, are not without risk. Mortality as a consequence of surgery may be as high as 20%. Successful surgery reduces symptoms and increases survival times and rates.
Surgery is usually designed (1) to take out the fibrous endomyocardium so that the ventricles can be filled with blood once more; (2) to repair or replace the mitral or tricuspid valve (or both), if one or another is involved; and (3) to leave a portion of fibrous endocardium in place to prevent postoperative heart block.
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