The Effects of Beta-Adrenergic Agents on the Contractility of Transplanted Canine Heart

Abstract

The effects of isoprenaline and adrenalin on the myocardial contractility of transplanted heart were studied in 6 mongrel dogs which had undergone orthotopic cardiac transplantation. Isoprenaline and adrenalin produced a fall in end-diastolic and end-systolic volumes, and an increase in stroke volume, cardiac output and velocity of contraction when the heart rate was increased. Similar changes were observed in 4 mongrel dogs tested as controls, with the exception of a less pronounced increase of cardiac output after administration of isoprenaline and adrenalin and a fall in stroke volume associated with a higher acceleration of heart rate after administration of isoprenaline. These minor differences between the transplanted and intact heart were thought to be a reflexion of the increased blood volume following heart transplantation.