Data-Driven Volume Thresholds Predictive of Improved Outcomes after Orthotopic Heart Transplantation

Abstract

It is well established that "high volume" centers have better outcomes for complex surgical care including transplantation. However, few studies have used data-driven methodology to establish clinically meaningful volume thresholds predictive of improved outcomes for centers performing orthotopic heart transplantation (OHT). All OHT cases performed between 2005 and 2015 (with follow-up through 2016) within the United Network for Organ Sharing (UNOS) database were reviewed for potential eligibility. All patients ≥18 years of age undergoing isolated OHT were included. Stratum-specific likelihood ratio analysis (SSLR) was used to establish volume thresholds predictive of the primary outcome of mortality at 1-year. Preoperative characteristics and postoperative outcomes were compared between volume strata using χ2 tests (categorical) or ANOVA (continuous). A total of 21,800 recipients (mean age 52.6 ± 12.8 years; 25.2% female) were included in the final cohort. Three distinct center volume strata were identified from the analysis: low (<10 OHT/year), intermediate (10-18 OHT/year), and high volume (≥19 OHT/year). More than half of recipients (57.4%) were transplanted at high volume centers. Compared to low volume centers, recipients at high volume centers had higher survival at 30-days and 1-year (96.0% vs 94.2% and 90.0% vs 86.6%, respectively; both P<.001). These recipients also had a lower rate of post-transplant dialysis (10.0% vs 12.8%; P<.001) despite higher rates of intra-aortic balloon pump and inotropic medication usage (table), along with shorter length of stay (20 days vs 23 days; P=.002). The results of our study demonstrate that higher volume centers perform better than their lower volume counterparts in terms of early mortality after OHT. Our study adds to the existing literature by providing specific, data-driven volume thresholds predictive of improved early outcomes in the contemporary transplant and circulatory support landscape.