Coronary vascular and myocardial lesions due to experimental constriction of the abdominal aorta.

The development and evolution of arterial and myocardial lesions were morphologically evaluated in Wistar rats submitted to constriction of the abdominal aorta. The control (sham-operated) and operated groups were evaluated 1, 2, 4 and 6 weeks after surgery. The aorta-constricted groups developed arterial hypertension followed by myocardial hypertrophy evidenced from the first week onwards by the increase in ventricular weight and in the diameters of left and right ventricular myofibers. The histopathologic study of the myocardium revealed in aorta-constricted groups, since the first week, widespread necrotizing changes of the intramural coronary branches surrounded by multifocal areas of myofiber degeneration and necrosis. The lesions were more extensive in the wall of the right ventricle and were gradually replaced by scar tissue. At the 6th week patchy focal fibrotic scars were found scattered in the myocardium of both ventricles. There were no systemic lesions in aorta-constricted or sham-operated groups. The close association between the arterial and myocardial lesions shows that muscle necrosis and scars are due to ischemia. They may influence the contractile performance of the myocardium in this model of pressure-induced hypertrophy of the heart.