Myocardiopathy in Chagas' disease: I. Comparative study of pathologic findings in chronic human and experimental Chagas' myocarditis

Pathologic findings in 29 individuals with a clinical picture of chronic Chagas' myocardiopathy are analyzed. Both macroscopic and microscopic changes are studied, and are correlated with similar findings in dogs infected with strains of Schizotrypanum cruzi. Flaccidity and dilatation was frequently found in both the human and experimental cases. Dilatation was more common in the right chambers of the hearts of the dogs, particularly in the right ventricle. Intramural thrombosis was frequent in human subjects (79.3 per cent), but was observed with less frequency in animals (11 per cent). Thinning of the wall and plaques of fibrosis were found, respectively, in 72.4 and 42 per cent of the cases in the human and animal groups. Parietal aneurysms localized in the areas of fibrosis and thinning were found in 27.6 per cent of the autopsy cases. Aneurysms of the wall were not found in dogs, but they were seen in the trabecular zone of the right ventricle in 7 animals. Aneurysms were of variable diameter (1 to 3 cm.) and disappeared when the animal died. Thinning of the wall by fibrous replacement of muscular tissue was found in all of the cases. The histologic pattern of the thin areas was similar in both groups; large areas of collagenous connective tissue at the subendocardial level were found. Also, islets of muscular bundles were found at midwall and subepicardium. They were particularly abundant in the latter localization. An electrocardiographic correlation demonstrated that epicardial unipolar leads obtained at the areas of fibrosis in dogs had the ventricular morphology of non-excitable zones. In human beings, ventriculograms of both supraventricular and ectopic ventricular origin always indicated the presence of areas of fibrosis, the localization and extent of which could always be determined by an analysis of the different leads.