Beneficial effects of estrogen on cardiac stunning in female rabbits

OBJECTIVE: To determine the effect of estrogen treatment on the contractile , relaxation, anc chronotropic responses of hearts of female rabbits to ces sation of perfusion. METHODS: Adult female rabbits were treated either with estradiol or with th e vehicle (control). The hearts were then isolated and perfused at constant pressure by the Langendorff technique. A saline-filled balloon connected t o a pressure transducer was inserted in the left ventricle in order to asse ss the mechanical function of the isolated heart. Cardiac stunning was indu ced by halting the perfusion of coronary vasculature for four successive pe riods of 1, 3, 5, and 5 minutes, followed by reperfusion between nonperfusi on periods. changes in cardiac function induced by the cessation of perfusi on were assessed by monitoring the changes in heart rate and in left ventri cular pressure ([dP/dt](max) as an index of ventricular contractility and [ dP/dt](min) as an index of ventricular relaxation). changes in coronary flo w were determined at baseline and following reperfusion. RESULTS: Halting coronary perfusion decreased (dP/dt)(max) and (dP/dt)(min) and slowed left ventricular contractions both in control and in estrogen-t reated hearts. The depressant effects of flow cessation on left ventricular (dP/dt)(max) and (dP/dt)(min) were smaller in estrogen-treated hears than in control hearts. Treatment with estrogen had no effect on the changes on the heart rate in responses to cessation of flow and to reperfusion. Treatm ent with estrogen increased coronary flow by 40%. Coronary reperfusion incr eased coronary flow transiently, but the effects did not differ significant ly between control and estrogen-treated hearts. CONCLUSIONS: Short-term treatment of adult female rabbits with doses of est rogen that are physiologic for the rabbit exerts a protective effect on car diac contractility from repetitive periods without perfusion. Copyright (C) 1999 by the Society for Gynecologic Investigation.