The effect of transplant center volume on cardiac transplant outcome. A report of the United Network for Organ Sharing Scientific Registry.

OBJECTIVE

The number of cardiac transplant programs continues to increase despite no increase in the number of hearts available for transplantation. As a result, the majority of heart transplant centers perform extremely small numbers of transplant operations annually. To determine the effect of small transplantation volume on transplant outcome, the following study was performed.

DESIGN

Using the Scientific Registry of the United Network for Organ Sharing, all cardiac transplant procedures from October 1987 through December 1991 were analyzed to determine whether center volumes affected cardiac transplant outcome. Patient survival rates for each center were determined, and the survival rates were modeled for the following patient variables: first transplantation or retransplantation, patient condition at the time of transplantation, patient underlying cardiac disease (congenital vs all others), and time.

SETTING

All cardiac transplant centers in the United States were included in the analysis.

PATIENTS

All patients undergoing cardiac transplantation in the United States from October 1987 through December 1991 were included in the analysis.

MAIN OUTCOME MEASURE

The primary end point in this analysis was mortality.

RESULTS

Throughout the entire study, of the 150 cardiac transplant centers, 35.3% of the centers were performing fewer than five cardiac transplantations per year, 53.3% were performing fewer than nine transplantations per year, and 61.3% were performing fewer than 12 transplantations per year, the minimum required for Medicare payment eligibility. Using the modeled survival rates, the risk of mortality decreased to a basal level in those centers performing between eight and 10 transplant operations per year. In centers performing fewer than nine transplantations, mortality increased sharply and exponentially. Dividing centers into those that performed nine or more transplantations per year (70 centers) and fewer than nine transplantations per year (80 centers), the increased risk of mortality at 1 month and 12 months was 40.3% and 33.1%, respectively, in centers performing fewer than nine cardiac transplantations per year (P < .001). Once the threshold of nine transplant procedures was met, those centers that were eligible for Medicare payment did not have significantly better survival than those centers not eligible for Medicare coverage.

CONCLUSIONS

These data demonstrate that the risk of mortality at early and intermediate time points is substantially higher in low-volume cardiac transplant centers, which make up more than half of the centers performing cardiac transplantation in the United States.