Size disparity between donor and recipient in canine heart transplantation

To assess the feasibility and function of small donor hearts for large recipients, small donor hearts were orthotopically transplanted into large recipients. Thirty adult mongrel dogs were used to form donor-recipient (D-R) combinations with the D-R heart weight ratio ranging from 0.47 to 1.78. In the D-R heart weight ratio of 0.8 or above (mean 1.11, Group I), the successful transplantation rate was 57 per cent, while it was 81 per cent in cases of less than 0.8 (mean 0.67, Group II) (no statistical difference). In 10 dogs (5 with D/R heart weight ratio greater than or equal to 0.8, 5 with less than 0.8) a recovery rate in cardiac function of the transplanted small heart was studied 2 hours following transplantation. There was no significant difference, hemodynamically in the normal range of left atrial pressure (LAP) between the two groups. The close relationship between cardiac output (CO) and volume load in the range of 10 to 15 mmHg of LAP was transformed to a linear function in the over 0.8 group. It was technically and hemodynamically possible to transplant small dog hearts to larger recipients up to the D-R heart weight ratio of 0.47. The importance of an adequate heart rate for the increase of CO in transplanted smaller donor hearts was emphasized.