Size matching in heart transplantation.

After heart transplantation, problems may arise from hearts that are either too small or too large. Although the "classic" rule requires that the donor/recipient weight ratio mismatch measure not less than 0.8, the chronic organ shortage led to a challenge of that margin. In selected cases donor/recipient weight mismatches of up to 0.5 may be accepted. In these circumstances, heterotopic heart transplantation may be an alternative. In pediatric heart transplantation, disproportionately large hearts (donor/recipient weight mismatches of 2.0 to 3.0) may create the so-called "big-heart syndrome," with coma and general convulsions. Treatment consists of peripheral pressure control with nifedipine.