Cardiac Performance in Experimental Adrenal Insufficiency in Cats

Abstract

Cardiac function was evaluated by ventricular function curves during the cardiovascular collapse observed in acute and chronic adrenal insufficiency. A progressive decline in peak cardiac work was observed in the acutely adrenalectomized cat (30% decrease at 1.8 hours and 50% at 3.5 hours after adrenalectomy). This impairment in cardiac work paralleled the decrease in mean arterial blood pressure which reached 50 mm Hg 3.5 hours after adrenalectomy. Cortisol and d -aldosterone, and the volume-expander, dextran, prevented a significant fall in mean arterial blood pressure and in peak cardiac work. When the mean arterial blood pressure of nonadrenalectomized cats was adjusted to follow the changes seen in adrenalectomized cats, a 49% depression in cardiac work resulted 3.5 hours after the initial decline in arterial blood pressure. The data suggest that the time course of the hypotension and presumed reduction in coronary perfusion pressure is sufficient to account for the large impairment in peak cardiac work observed. Cardiac work was reduced 56% in chronically adrenalectomized cats 8 to 10 days after adrenalectomy. Dexamethasone and deoxycorticosterone acetate, administered separately, prevented significant myocardial impairment. Since the mean arterial blood pressure of conscious, chronically adrenalectomized cats was normal, the myocardial depression was not secondary to inadequate coronary perfusion in chronic adrenal insufficiency and thus represents direct impairment of myocardial performance.