Unrepairable congenital heart valve disease is an unsolved problem in pediatric cardiac surgery because there are no growing heart valve implants. Partial heart transplantation is a new type of transplant that aims to solve this problem. In order to study the unique transplant biology of partial heart transplantation, animal models are necessary. This study aimed to assess the morbidity and mortality of heterotopic partial heart transplantation in rodent models. This study assessed two models. The first model involved transplanting heart valves from donor animals into the abdominal aortic position in the recipient animals. The second model involved transplanting heart valve leaflets into the renal subcapsular position of the recipient animals. A total of 33 animals underwent heterotopic partial heart transplantation in the abdominal aortic position. The results of this model found a 60.61% (n = 20/33) intraoperative mortality rate and a 39.39% (n = 13/33) perioperative mortality rate. Intraoperative mortality was due to vascular complications from the procedure, and perioperative mortality was due to graft thrombosis. A total of 33 animals underwent heterotopic partial heart transplantation in the renal subcapsular position. The results of this model found a 3.03% (n = 1/33) intraoperative mortality rate, and the remaining 96.97% survived (n = 32/33). We conclude that the renal subcapsular model has a lower mortality rate and is technically more accessible than the abdominal aortic model. While the heterotopic transplantation of valves into the abdominal aortic position had significant morbidity and mortality in the rodent model, the renal subcapsular model provided evidence for successful heterotopic transplantation.

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Objectives Heart allocation policy (HAP) in the US was changed in October 2018. The aim of this study was to assess the effect of the new policy on racial disparities in heart transplantation (HT) outcomes. Methods: The United Network for Organ Sharing (UNOS) registry was used to identify adult patients undergoing isolated HT between 2010-2021. Patients were stratified into pre-HAP (January 2010 to September 2018) vs. post-HAP (October 2018 to September 2021). Recipient race was classified as White, Black, Hispanic, or Other. The primary outcome was post-HT mortality. Cox proportional hazard models were used for risk-adjustment in evaluating the independent effect of race on mortality. Results A total of 27,403 patients underwent HT in 143 centers during the study period. The proportion of non-whites undergoing HT increased in the post-HAP era: (pre-HAP: White 66.0%, Black 21.2%, Hispanic 8.2%, Other 4.6% versus post-HAP: White 62.5%, Black 23.2%, Hispanic 9.5%, Other 4.8%; p<0.001). In risk-adjusted analysis, Black recipients were at higher risk of post-HT mortality in the pre-HAP era (HR 1.31, 95% CI 1.22-1.41; p<0.001) but not in the post-HAP era (HR 1.12, 95% CI 0.03-1.34; p=0.222) compared to White recipients. Other non-white recipients had comparable risk-adjusted post-HT mortality rates compared to White recipients both in the pre- and post-HAP eras. Conclusions: Under the new heart allocation system, a higher percentage of recipients are non-white. In addition, racial disparities in outcomes have improved with Black recipients no longer having an increased adjusted risk of mortality following HT.

Objectives. Heart transplantation (HT) is a definitive therapy for refractory heart failure, making it the gold-standard treatment for recipients with end-stage disease. Heart allocation policy (HAP) in the United States was changed on October 18th, 2018. The aim of this study was to assess the effect of the new policy on racial disparities in heart transplantation (HT) outcomes. Methods. The United Network for Organ Sharing (UNOS) registry was used to identify adult recipients undergoing isolated HT between 2010 and 2021. Recipients were stratified into pre-HAP (January 2010 to September 2018) vs. post-HAP (October 2018 to September 2021). Recipient race was classified as White, Black, Hispanic, or other. The primary outcome was post-HT mortality. Cox proportional hazard models were used for risk-adjustment in evaluating the independent effect of race on post-HT mortality. Results. A total of 27,403 recipients underwent HT in 143 centers during study period. The proportion of non-Whites undergoing HT increased in the post-HAP era: (pre-HAP: White 66.0%, Black 21.2%, Hispanic 8.2%, Other 4.6% versus post-HAP: White 62.5%, Black 23.2%, Hispanic 9.5%, Other 4.8%; p < 0.001 ). In risk-adjusted analysis, Black recipients were at higher risk of post-HT mortality in the pre-HAP era (HR 1.31, 95% CI 1.22–1.41; p < 0.001 ) but not in the post-HAP era (HR 1.12, 95% CI 0.03–1.34; p = 0.222 ) compared to White recipients. Other non-White recipients had comparable risk-adjusted post-HT mortality rates compared to White recipients both in the pre-HAP and post-HAP eras. Conclusions. Under the new heart allocation system, a higher percentage of recipients are non-White. In addition, racial disparities in HT outcomes have improved with Black recipients no longer having an increased risk-adjusted mortality following HT.