Cardiac autonomic denervation in congestive heart failure: Comparison of Chagas' heart disease with other dilated cardiomyopathy

Congestive heart failure (CHF) is associated with activation of the cardiac sympathetic nerves. However, impairment of the sympathetic nerve terminals in patients with CHF has been indicated by studies showing reduction of cardiac norepinephrine uptake and stores. This investigation studies the histochemical evaluation of the sympathetic nerve terminals in CHF. The cardiac parasympathetic innervation was also studied to address the question of specificity of the presumed sympathetic denervation. Nineteen patients with CHF underwent cardiac transplantation or partial ventriculectomy, which provided the heart tissue. In 11 of them, the dilated cardiomyopathy was associated with Chagas' disease. Inflammatory process and fibrosis were studied histologically. The sympathetic and parasympathetic nerve fibers were visualized through histochemical techniques for, respectively, catecholamines and acetylcholinesterase activity. By using a computer-assisted morphometric program, the inflammation, fibrosis, and parasympathetic innervation were quantified. Moderate to severe fibrosing myocarditis characterized the hearts of the chagasic patients. In cardiomyopathies not associated with Chagas' disease, the inflammation was discrete, if present, but the amount of fibrosis was similar to that found in Chagas' cardiomyopathy. Reduction of both kinds of nerve terminals occurred in the heart of all patients. The parasympathetic denervation was proven to be more severe in chagasic cardiomyopathy. Our data on the heart innervation indicate a progressive autonomic denervation in heart failure. In Chagas' heart disease, the denervation seems to be more severe or rapid, probably because of the sustained inflammatory process.