Catecholamine-induced experimental cardiomyopathy--a histopathological, histochemical and ultrastructural study.

An experimental model of myocardiopathy was induced in rhesus monkeys following noradrenaline (NA) infusion (20 ug/kg body wt/minute), for a period of 2 hours daily for three consecutive days. The animals were sacrificed after two hours (acute phase), forty-eight hours (sub-acute phase) and twenty-one days (chronic phase). Focal depletion of succinic dehydrogenase, increase in adenosine triphosphatase, acid phosphatase and appearance of large fat droplets in myocardial muscle was noted in the acute phase. Histopathological examination revealed focal edema, opacity and fuchsinorrhagia of the muscle fibres distributed in both the ventricles. Myofibrillar degeneration, myocytolysis and vacuolization with aggregation of lymphomononuclear cells were the significant features in the acute phase. During sub-acute and chronic phases, these features became less prominent and reparative changes with proliferation of fibroblasts became more marked. By the twenty-first day, irregular, focal scars replaced the necrosed myocardium. Ultrastructurally, heart muscle showed myofibrillar disorganisation, distortion of Z and A bands, dilatation of sarcoplasmic reticulum and swelling and rupture of mitochondria. Altered membrane permeability was evidenced by the presence of reaction products of horseradish peroxidase within the cardiac cells. In the reparative phase, however, myocytolytic changes regressed and collagen deposition was the prominent feature. This experimental study has several histological features simulating human cases of myocardial infarction without coronary occlusion.