A wide range of disorders give rise to eosinophil counts greater than 1.5 X 10(9)/l (hypereosinophilia) and cardiac injury. The best known of these is eosinophilic endomyocardial disease (Löffler's endomyocardial fibrosis), which occurs as a major complication of the idiopathic hypereosinophilic syndrome. Here the heart damage appears to be a direct result of tissue injury produced by toxic eosinophil granule proteins within the heart. However, it is not known what causes the eosinophilia in these patients, why the eosinophils degranulate, or why the endocardium is especially susceptible to this type of injury. A number of parasitic infections may give rise to eosinophilic myocarditis. This is usually the result of the presence of the parasites within the myocardium where they die within inflammatory lesions, which may be extensive. Occasionally, drug reactions and rejection of a transplanted heart may produce eosinophilic myocarditis. Allergic granulomatosis and vasculitis (the Churg-Strauss syndrome), which gives rise to granulomas involving the myocardium, and eosinophilic (hypersensitivity) myocarditis usually respond rapidly to treatment with steroids. However, diffuse myocardial involvement may lead to heart failure, and some of these patients may later develop dilated cardiomyopathy. It is concluded that the heart may be affected by a variety of diseases in which eosinophils are a prominent component in the inflammatory cell infiltrates. Eosinophils themselves may contribute to some of the myocardial cell injury which occurs in these diseases, and attempts to limit this with steroids may be worthwhile in some patients.
Fourteen cases of heart disease with hypereosinophilia were analyzed employing conventional cardiologic methods, including echocardiography, cardiac catheterization, and endomyocardial biopsy. The cases were divided into four types: Acute carditic (endocarditis, myocarditis, pericarditis; five cases); ventricular dilation (three cases); restrictive (three cases); electric disturbance (three cases). Biopsy revealed significant changes in all cases. In one case of the ventricular dilation type, endomyocardial fibrosis with myocardial degeneration was seen, and in another case mural thrombus formation was shown to be present. In three cases of the restrictive type, endomyocardial fibrosis (EMF) was observed. In two cases of the electric disturbance type, minor right ventricular myocardial degeneration was observed. In two of the three cases of the carditic type and in three of eight cases in other categories, postmyocarditic changes were observed. The course of the disease compared with the type of disorder revealed a short course in the carditic type and a longer course, ranging from 2 to 24 years, with one exception, in the other types. It is also confirmed that the various histopathologic changes can be related to particular clinical presentations. We have shown that the basic changes in eosinophilic heart disease are not restricted to the endomyocardium and that they occur in various parts of the heart causing more widespread manifestations. The more comprehensive term "eosinophilic heart disease" is a preferable description.
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