Prevention of Congestive Heart Failure in Rabbits With Severe Aortic Constriction

¹ From the Department of Physiology, School of Medicine, University of Southern California, Los Angeles, California

A severe aortic constriction induces hypertension followed by death from congestive heart failure within 8 days in the majority of rabbits. The present study was planned to find out if previous successful cardiac adaptation to moderately elevated pressure could prevent congestive heart failure or prolong survival time following severe aortic constriction. A three-stage operative procedure was used to vary the cross-sectional area of the aorta. A moderate degree of aortic constriction was induced for 4 or 7–13 (average 10) days during which time arterial pressure rose. The constriction was removed, pressures fell to within normal limits after 3–7 days and then the severe aortic stricture was applied. The presence of elevated pressure for more than a week after moderate constriction protected six of seven animals from the heart failure inducing effects of a severe aortic stricture. The seventh animal developed heart failure and died after 24 days. After less than a week of elevated pressure, survival was prolonged to 21–27 days in three of four animals, and heart failure was prevented in the fourth animal. At no time was bradycardia observed and sometimes high heart rates occurred when pressure reached new high values after the severe stricture. The pressure suddenly dropped for short periods in several animals, but they retained their ability to develop high pressure; something never observed in animals with no previous pressure elevation.

Note:
with the technical assistance of Marjorie J. DeCuir