FIBROSIS AND INFLAMMATORY CELLS IN HUMAN CHRONIC CHAGASIC MYOCARDITIS- SCANNING ELECTRON-MICROSCOPY AND IMMUNOHISTOCHEMICAL OBSERVATIONS

The present study deals with both pathologic fibrosis and matrix conne ctive tissue in chronic chagasic myocarditis. A total of 12 hearts wer e obtained at autopsy. Eight cases of chronic chagasic myocarditis wer e selected. Four cases without evidence of cardiac disease were used a s controls. The diagnosis of chronic Chagas' heart disease was based o n previously established criteria. A cell-maceration method was utiliz ed to evaluate the spatial organization of the fibrillar collagen accu mulation after removal of the myocardial tissue non-fibrous elements. The relationship between inflammatory cells identified by monoclonal a ntibodies and interstitial fibrosis stained with picrosirius red was a ssessed. Striking structural alterations of the collagen matrix in the perimysium were detected: increase in number and thickness of tendon- like structures, and markedly thickened and aggregated collagen strand s. Besides, a diffuse increase in the thickness of collagen fibers sur rounding individual myocytes, consisting of the endomysial matrix, mai nly adjacent to the perimysium, could be observed. The dense-weave end omysial meshwork was composed of fine collagen fibrils, and it was con tinuous with those of adjacent myocytes, obscuring the lateral struts. Sometimes, thicker struts tethering myocytes to myocytes could be see n. These changes were associated with scattered dense scar-like foci, probably reflecting repair fibrosis associated with myocyte necrosis. Furthermore, the present results clearly showed the colocalization of foci of myocyte necrosis and degeneration and associated fibrosed area s and fibroblasts with T lymphocytes and macrophages. The accumulation of interstitial collagen fibers in chronic chagasic myocarditis may b e expected to decrease myocardial compliance and disrupt synchronous c ontraction of the ventricles during systole, contributing to a spectru m of ventricular dysfunction that involve either the diastolic or syst olic phase of the cardiac cycle or both. Myocardial fibrosis can be al so implicated in the genesis of malignant ventricular tachyarrhythmias , major causes of sudden death among chronic chagasic patients. The in crease in myocardial fibrosis could be directly related to an inflamma tory reaction mainly composed of T lymphocytes and macrophages. (C) 19 98 Elsevier Science Ireland Ltd. All rights reserved.