Chronic Chagas' Myocardiopathy (CCM)

Köberle and others believed that the cardiomegaly is caused by the same basic disturbance of intrinsic innervation as has been demonstrated in the alimentary tract. Most pathologists agree there is a marked reduction in identifiable ganglion cells in the heart. Microscopically, there is a diffuse inflammation of the myocardium involving the walls of all chambers, including the septum, and sometimes extending into the endocardium and epicardium. The valves and coronary arteries are not affected. Endomyocardial fibrosis and thinning occur, particularly at the apex of the left ventricle, where aneurysmal dilatation may develop in over 50%, and in some reports as many as 86%, of patients who come to autopsy (Fig. 4.27). Possible mechanisms for development of these apical aneurysms include ischemia, inflammation, herniation through the apical spiral bundles, or autonomic imbalance. There are frequently mural thrombi in the aneurysm or the apex of the ventricles or attached elsewhere to the endocardium of the atria or ventricles. The involvement of the right ventricle, as well as the left, with fibrotic areas and the presence of the apical aneurysms help to differentiate CCM from other cardiomyopathies.

Grossly, the cardiac chambers are all dilated and the muscles are flaccid. The dilatation widens the tricuspid and mitral annuli and leads to incompetence of those valves with functional tricuspid and mitral regurgitation. There is hypertrophy of the myocardium. The heart weight increases, in some cases up to 800 gm.

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Fig. 4.27 Chronic Chagas' myocardiopathy. (A) Chronic myocarditis with interstitial edema, fibrosis and mild inflammatory cell infiltrate. H & E x 8O. AFIP 62-6106. (B) Necropsy specimen of an enlarged heart in a 36-year-old black Brazilian woman with chronic Chagas' myocardiopathy. The myocardium is pale and there is generalized dilatation of the cardiac chambers. Note the aneurysm of the left ventricle at its apex and notched appearance of the apical aspect of the interventricular septum. AFIP 69-2961 -1. (C) Posterior half of the same heart showing generalized dilatation of the atria and ventricles and the aneurysm at the apex of the left ventricle. The interventricular septum and ventricular walls are thin, as is the complexity of trabeculae near the insertion of the papillary muscles. AFIP 69-2961-2. (D) Moderate generalized cardiac enlargement is noted on PA view of the chest of the same patient. Fluoroscopically, the cardiac pulsations were diminished. Note the clear lung fields with no pulmonary vascular congestion or pleural fluid. Clinically the patient had shortness of breath, cardiac palpitations, precordial pain and pitting edema in the legs for 15 days prior to admission. The ECG showed supraventricular tachycardia and evidence of anteroseptal necrosis, with extension to the diaphragmatic area. Chagas' serology was positive. The patient progressively deteriorated and at autopsy the heart weighed 420 gm and showed generalized enlargement with apical aneurysm. (Courtesy of Dr. Clovis Simao, Sao Paulo).