Orthotopic cardiac xenografting in the newborn goat

Fourteen newborn (less than 7 days) goats were subjected to orthotopic cardiac transplantation with donor xenografts from size-matched lambs. Ten goats survived the operation (greater than 24 hours). Recipient animals received cyclosporine 48 and 24 hours before the operation and daily after the operation on a gradually reducing daily protocol. Recipients were also given pulse doses of methylprednisolone (100 mg/kg) and azathioprine (3 mg/kg) once a week, the dosage schedule being gradually reduced and azathioprine discontinued as recipients became long-term survivors (greater than 60 days). Seven recipients had radionuclide left ventriculography for measurement of left ventricular ejection fraction from 1 to 4 months postoperatively. Ejection fractions at 1 month in two recipients were 35% and 57%, and at 2 months the ejection fraction in one recipient was 58%. Serial ejection fractions from 1 to 4 months postoperatively in four recipients averaged 50%, 58%, 45%, and 45%. Survival in days among the 10 recipients was 24, 32, 44, 47, 60, 60, 78, 90, 120, and 165. Average survival was 72 days. There were no significant infections. Most animals showed mild-to-moderate subacute and chronic graft rejection at autopsy. One host showed no gross or microscopic graft rejection at autopsy on postoperative day 47. Tumor was not observed. These data suggest that long-term survival may be feasible for newborn recipients of cardiac xenografts with cyclosporine therapy and limited supplemental immunosuppression.