To determine the effects of donor/recipient weight mismatch on allograft function and survival after orthotopic heart transplantation, we retrospectively compared the clinical and the hemodynamic characteristics of recipients weighting more than their donor (\u27\u27undersized\u27\u27) with those of recipients weighting less than their donor (\u27\u27oversized\u27\u27). The median follow-up period was 24 months (range, 0 to 67 months). In 88 patients (59%) donor weight was 1% to 46% less than recipient weight (13.5 ± 8.9 x ± SD). In 61 patients (41%) donor weight exceeded recipient weight by 0% to 139% (20% ± 23%). When recipient ideal body weight was used in the analysis, 75 patients (51%) were undersized by 1% to 59% (13% ± 10%), and 72 patients (49%) were oversized by 0% to 67% (19% ± 18%). Preoperative transpulmonary gradient, ventricular function, and exercise tolerance were similar in the two groups. The number and severity of episodes of rejection and infection after transplantation were also similar in the two groups 1, 6, and 12 months after transplantation. When recipient ideal weight was used in the analysis, right ventricular (RV) and left ventricular (LV) ejection fractions (EFs) were within normal limits (RVEF \u3e 40%; LVEF ≥ 45%) and similar in the two groups. When recipient actual weight was used in the analysis, the LVEF measured at 12 months after heart transplantation was higher in the oversized than in the undersized group (52 ± 11 vs 46 ± 10; p \u3c 0.05). Postoperative hemodynamic values and exercise were similar in the two groups regardless of whether recipient weight or ideal body weight were used in the analysis. Forty-six recipients died 0 to 46 months (median, 7 months) after orthotopic heart transplantation. In a Cox regression model, recipients with donor weight greater than recipient ideal weight had a significantly greater risk of death within the follow-up period than did recipients with donor weight less than recipient ideal weight (relative risk = 2.19; p \u3c 0.05). When percent donor weight/recipient ideal weight mismatch was used as a continuous variable, donor heart oversizing was negatively related to survival, independent of preoperative transpulmonary gradient values (p \u3c 0.05). In contrast to common belief, oversizing of donor hearts does not improve the outcome of orthotopic heart transplant recipients who have reversible preoperative pulmonary hypertension. Acceptance of undersized donor hearts is not detrimental to allograft function and recipient survival. Use of undersized donor hearts may maximize the use of critically scarce donor organs
