The present study deals with both pathologic
fibrosis and matrix connective tissue in chronic chagasic
myocarditis. A total of 12 hearts were obtained at autopsy. Eight cases of chronic chagasic
myocarditis were selected. Four cases without evidence of
cardiac disease were used as controls. The diagnosis of chronic Chagas'
heart disease was based on previously established criteria. A cell-maceration method was utilized to evaluate the spatial organization of the
fibrillar collagen accumulation after removal of the myocardial tissue non-fibrous elements. The relationship between inflammatory cells identified by
monoclonal antibodies and interstitial
fibrosis stained with
picrosirius red was assessed. 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 strands. Besides, a diffuse increase in the thickness of
collagen fibers surrounding individual myocytes, consisting of the endomysial matrix, mainly adjacent to the perimysium, could be observed. The dense-weave endomysial meshwork was composed of fine
collagen fibrils, and it was continuous with those of adjacent myocytes, obscuring the lateral struts. Sometimes, thicker struts tethering myocytes to myocytes could be seen. 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 areas and fibroblasts with T lymphocytes and macrophages. The accumulation of interstitial
collagen fibers in chronic chagasic
myocarditis may be expected to decrease myocardial compliance and disrupt synchronous contraction of the ventricles during systole, contributing to a spectrum of
ventricular dysfunction that involve either the diastolic or systolic phase of the cardiac cycle or both. Myocardial
fibrosis can be also implicated in the genesis of malignant
ventricular tachyarrhythmias, major causes of
sudden death among chronic chagasic patients. The increase in myocardial
fibrosis could be directly related to an inflammatory reaction mainly composed of T lymphocytes and macrophages.