Size Matching and Combined Heart Kidney Transplantation - UNOS Registry Analysis

Purpose Optimal size-matching metrics for prediction of outcomes after combined heart-kidney transplantation (HKT) are unknown. Methods Combined HKTs performed between January 2000 and April 2019 were analyzed using United Network of Organ Sharing registry. Size metrics (weight, height, body mass index (BMI) and predicted heart mass (PHM)) were divided into seven equally sized groups using donor-to-recipient ratio. Kaplan-Meier survival and Cox proportional hazard analyses were performed to assess composite risk of mortality or re-transplantation at 1-year. Results A total of 1,290 recipients were analyzed; 155 events occurred (n=153 deaths; n=4 re-transplants). Compared to a well-matched cohort, severe under-sizing by either PHM (0.56 to 0.85; hazard ratio (HR) 1.77, 95% confidence interval (CI) 1.02-3.08, p=0.042) or weight (0.50 to 0.80; HR 2.00, 95% CI 1.14-3.52, p=0.015), but not BMI and height, was associated with an increased risk of events. Upon categorizing recipients into 4 groups based on presence or absence of severe under-sizing by either PHM or weight ratio, those whose donors were severely undersized for both were at significantly higher risk of poor outcomes (HR 2.74, 95% CI 1.78-4.19, p Conclusion Recipients of combined HKT whose donors were severely undersized based on both weight ratio and PHM had significantly worse outcomes compared to those whose donors were severely undersized by either parameter alone or not at all.