Acute rejection often leads to severe
myocardial failure and death. The beneficial hemodynamic effects of
isoproterenol in improving immediate postoperative
heart failure have prompted its routine use after
transplantation. However, because of the physiopathological alterations documented during rejection, an inappropriate response of the graft to
isoproterenol administration could be expected. Six dogs received orthotopic transplants and were prepared with implantable devices for serial hemodynamic studies. The studies were performed on the resting unanesthetized subject 3 hours after operation when transient
heart failure was present and repeated when
myocardial failure secondary to rejection occurred. After basal state measurement, various doses of
isoproterenol were infused and the hemodynamic responses during each period were compared. During rejection, the hemodynamic response to 0.05 and 0.10 micrograms.kg-1.min-1 was significantly lower when compared with the response in the postoperative period. To achieve similar postoperative chronotropic and inotropic effects, 0.35 microgram.kg-1.min-1 of
isoproterenol was necessary.
Isoproterenol is therefore effective in controlling
myocardial failure during acute rejection despite a reduced sensitivity of the sinoatrial node and myocardial tissue.