Background: Previous studies have demonstrated a relationship between increasing center volume and cardiac transplant outcomes. The purpose of this study was to confirm a relationship between post-heart transplant outcomes and center experience and to determine whether this relationship persists among low- and high-risk heart transplant recipient-donor pairs.
Methods and results: The United Network for Organ Sharing (UNOS) provided deidentified patient-level data. Analysis included 8029 heart transplant recipients aged ≥18 years and transplanted between January 1, 2001 and December 31, 2006 with follow-up available through February 3, 2009. The primary outcome was observed 1-year posttransplant graft survival. Multivariable logistic regression was used to calculate expected 1-year survival for recipients. Threshold analysis identified 3 discrete risk groups of transplant recipients: high-risk, moderate-risk, and low-risk. Three discrete risk strata for center volume: low (<10.5 recipients/yr), intermediate (10.5 to 47 recipients/yr), and high (>47 recipients/yr) were also identified. χ(2) test was used to compare 1-year survival at low- and intermediate- with high-volume centers. In multivariable logistic regression analysis, annual center volume was significantly associated with posttransplant graft survival at 1 year (odds ratio [OR]=0.995, 0.992 to 0.999; P=0.010) and primary graft failure (OR=0.985, 0.972 to 0.997; P=0.015), but not stroke (OR=0.996, 0.990 to 1.003; P=0.295), infection (OR=1.001, 0.998 to 1.003; P=0.613), or dialysis (OR=1.001, 0.997 to 1.005; P=0.522). Log-rank test demonstrated significant difference in survival between volume groups with respect to high-risk (P=0.0032) and low-risk (P=0.00415), but not moderate-risk (P=0.128) patients.
Conclusions: A direct relationship existed between increasing center volume and improved graft survival. Across all recipient-donor pair risk strata, posttransplant graft survival at 1 year was significantly lower at low-volume centers. The volume-outcomes relationship was strongest in the highest-risk recipient-donor category.