When good intentions turn bad: A need for course correction

Allocation changes in heart transplantation: What has really changed?

OBJECTIVE

In 2018, the heart allocation system changed status classifications and broadened geographic distribution. We examined this change at a national level based on the immediate pre- and postchange periods.

METHODS

Using the Scientific Registry of Transplant Recipients database, we identified all adult primary, isolated heart transplants from October 18, 2017, to October 17, 2019. Two time periods were compared: (1) October 18, 2017, to October 17, 2018 (pre); and (2) October 18, 2018, to October 17, 2019 (post). Comparisons were made between groups, and a multivariable logistic regression model was created to identify factors associated with pretransplant temporary mechanical circulatory support. Volume analysis at the regional, state, and center level was also conducted as the primary focus.

RESULTS

A total of 5381 independent heart transplants were identified within the time frame. On unadjusted analysis, there was a significant increase in temporary mechanical circulatory support (pre, 11.1%; post, 36.2%, P < .01) and decrease in waitlist days (pre, 93 days; post, 41 days; P < .01). Distance traveled (nautical miles) (pre, 83; post, 225; P < .01) and ischemic time (hours) (pre, 3.0; post, 3.4; P < .01) were significantly increased. On multivariable analysis, the postallocation time period was independently associated with temporary MCS (odds ratio, 4.463; 95% confidence interval, 3.844-5.183; P < .001). Transplant volumes did not significantly change after the allocation change at a regional, state, and center level.

CONCLUSIONS

Since the planned alteration to the allocation system, there have been changes in the use of temporary mechanical circulatory support as well as distance and ischemic time associated with transplant, but no significant volume changes were observed. Continued observation of outcomes and volume under the new allocation system will be necessary in the upcoming years.

An updated estimate of posttransplant survival after implementation of the new donor heart allocation policy

The Organ Procurement and Transplant Network (OPTN) implemented a new heart allocation policy on October 18, 2018. Published estimates of lower posttransplant survival under the new policy in cohorts with limited follow-up may be biased by informative censoring. Using the Scientific Registry of Transplant Recipients, we used the Kaplan-Meier method to estimate 1-year posttransplant survival for pre-policy (November 1, 2016, to October 31, 2017) and post-policy cohorts (November 1, 2018, to October 31, 2019) with follow-up through March 2, 2021. We adjusted for changes in recipient population over time with a multivariable Cox proportional hazards model. To demonstrate the effect of inadequate follow-up on post-policy survival estimates, we repeated the analysis but only included follow-up through October 31, 2019. Transplant programs transplanted 2594 patients in the pre-policy cohort and 2761 patients in the post-policy cohort. With follow-up through March 2, 2021, unadjusted 1-year posttransplant survival was 90.6% (89.5%-91.8%) in the pre-policy cohort and 90.8% (89.7%-91.9%) in the post-policy cohort (adjusted HR = 0.93 [0.77-1.12]). Ignoring follow-up after October 31, 2019, the post-policy estimate was biased downward (1-year: 82.2%). When estimated with adequate follow-up, 1-year posttransplant survival under the new heart allocation policy was not significantly different.

Paradoxical outcome of heart transplantation associated with institutional case volume

BACKGROUND

Previous studies in heart transplantation have shown an association between institutional case volume and outcomes. We aim to determine the case volume associated with optimal 1-year survival after transplantation.

METHODS AND RESULTS

The United Network for Organ Sharing (UNOS) national database was analyzed for adult patients who underwent orthotopic heart transplantation between January 2013 and December 2017. A total of 11,196 cases at 128 transplant centers were included. Risk-adjusted restricted cubic splines revealed a non-linear association between institutional case volume and 1-year post-transplant survival. In the risk-adjusted, random-effect Cox model with segmented linear splines, higher heart transplant volume up to 24 cases per year was associated with better 1-year survival (HR = .978 every additional case, 95% CI .963-.993), and optimal survival was maintained between 24 and 38 cases per year. However, further increase in volume above 38 transplants per year was associated with mildly decreased 1-year survival (HR = 1.007 every additional case, 95% CI 1.002-1.013).

CONCLUSIONS

The relationship between institutional case volume and heart transplant 1-year survival is non-linear, with optimal survival observed at institutional case volume of 24-38 cases per year.