CARDIOVASCULAR ACTIONS OF ATRIAL-NATRIURETIC-FACTOR IN SHEEP WITH CARDIAC-FAILURE

The present study examines in detail the shortterm cardiovascular acti ons of atrial natriuretic factor (ANF) in sheep with experimental low- output cardiac failure. Five conscious sheep, surgically implanted wit h a ventricular pacing wire, were paced at 220 beats/min for 14 days. Most clinical symptoms of congestive heart failure (CHF) were apparent after the 14 days, characterized by low cardiac output, high venous p ressure, increased total peripheral resistance, increased plasma level s of ANF, noradrenaline, arginine vasopressin and renin, and marked fl uid retention. On day 14 of pacing, intravenous infusion of ANF at 100 mu g/h for 60 min restored cardiac output to prepacing values and red uced both total peripheral resistance and right atrial pressure. These effects were sustained throughout the infusion period. No change was seen in blood pressure, plasma renin, or noradrenaline levels. These h emodynamic changes, produced by short-term infusion of ANF, contrasted with those seen in normal sheep, where there was a fall in cardiac ou tput with increased total peripheral resistance. These changes reflect a return toward normal of the left ventricular function curve. This i s the first study to report that ANF improves cardiac function in cons cious sheep with CHF, primarily by a vasodilator action to reduce card iac preload, and suggests that ANF may be useful in treating the hemod ynamic effects associated with cardiac failure.