Heart Allocation in the United States

Impact of the New Heart Allocation System on the Medium-Term Outcomes in Patients With Hypertrophic Cardiomyopathy

The introduction of the new heart allocation system in the United States in 2018 resulted in an increase in the number of heart transplants (HT) performed among patients with hypertrophic cardiomyopathy (HCM). However, whether that affected medium-term post-HT outcomes in this group of patients remains unknown. We conducted an analysis of the United Network for Organ Sharing Transplant Database, including adults with HCM who underwent heart transplantation between 2015 and 2021. Patients were divided into two equal-duration eras: Era 1 (October 17, 2015, to October 17, 2018) and Era 2 (October 18, 2018, to October 18, 2021). In the studied period, 444 patients with HCM underwent HT: 204 in Era 1 and 240 in Era 2. In Era 2, the waitlist time was shorter, transplant rates were higher, patients were less frequently supported with inotropes but more often with an IABP, ischemic time was longer, and donor-to-recipient distance larger. Pre- and post-transplant functional status was comparable across the two eras, while the pre-HT employment rate was higher in the new system. The 3 year survival was unchanged across eras. In the new allocation system, despite more frequent mechanical circulatory support (MCS) use and increased ischemic time, the medium-term outcomes of patients with HCM remained favorable.

Veno-Arterial Extracorporeal Membrane Oxygenation as a Bridge to Heart Transplant-Change of Paradigm

Despite advances in medical therapy and mechanical circulatory support (MCS), heart transplant (HT) remains the gold standard therapy for end-stage heart failure. Patients in cardiogenic shock require prompt intervention to reverse hypoperfusion and end-organ damage. When medical therapy becomes insufficient, MCS should be considered. Historically, it has been reported that critically ill patients bridged with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) directly to HT have worse outcomes. However, when the heart allocation system gives the highest priority to patients on VA-ECMO support, those patients have a higher incidence of HT and a lower incidence of death or removal from the transplant list. Moreover, patients with a short waiting time on VA-ECMO have a similar hazard of mortality to non-ECMO patients. According to the reported data, bridging with VA-ECMO directly to HT may be a solution in the selection of critically ill patients when the anticipated waiting list time is short. However, when a prolonged waiting time is expected, more durable MCS should be considered. Regardless of the favorable results of the direct bridging to HT with ECMO in selected patients, the superiority of this strategy compared to the bridge-to-bridge strategy (ECMO to durable MCS) has not been established and further studies are mandatory in order to clarify this issue.

Decreased frequency of transplantation and lower post-transplant survival free of re-transplantation in LVAD patients with the new heart transplant allocation system

PURPOSE

To evaluate the effect of the new heart transplant (HT) allocation system in left ventricular assist device (LVAD) supported patients listed as bridge to transplantation (BTT).

METHODS

Adult patients who were listed for HT between October 18, 2016 and October 17, 2019, and were supported with an LVAD, enrolled in the UNOS database were included in this study. Patients were classified in the old or new system if they were listed or transplanted before or after October 18, 2018, respectively.

RESULTS

A total of 3261 LVAD patients were listed for transplant. Of these, 2257 were classified in the old and 1004 in the new system. The cumulative incidence of death or removal from the transplant list due to worsening clinical status at 360-days after listing was lower in the new system (4% vs. 7%, P = .011). LVAD Patients listed in the new system had a lower frequency of transplantation within 360-days of listing (52% vs. 61%, P < .001). A total of 1843 LVAD patients were transplanted, 1004 patients in the old system and 839 patients in the new system. The post-transplant survival at 360 days was similar between old and new systems (92.3% vs. 90%, P = .08). However, LVAD patients transplanted in the new system had lower frequency of the combined endpoint, freedom of death or re-transplantation at 360 days (92.2% vs. 89.6%, P = .046).

CONCLUSION

The new HT allocation system has affected the LVAD-BTT population significantly. On the waitlist, LVAD patients have a decreased cumulative frequency of transplantation and a concomitant decrease in death or delisting due to worsening status. In the new system, LVAD patients have a decreased survival free of re-transplantation at 360 days post-transplant.

Changes in heart transplant waitlist and posttransplant outcomes in patients with restrictive and hypertrophic cardiomyopathy with the new heart transplant allocation system

Historically, patients with restrictive (RCM) and hypertrophic cardiomyopathy (HCM) experienced longer wait-times for heart transplant (HT) and increased waitlist mortality. Recently, a new HT allocation system was implemented in the United States. We sought to determine the impact of the new HT system on RCM/HCM patients. Adult patients with RCM/HCM listed for HT between November 2015 and September 2019 were identified from the UNOS database. Patients were stratified into two groups: old system and new system. We identified 872 patients who met inclusion criteria. Of these, 608 and 264 were classified in the old and new system groups, respectively. The time in the waitlist was shorter (25 vs. 54 days, P < .001), with an increased frequency of HT in the new system (74% vs. 68%, P = .024). Patients who were transplanted in the new system had a longer ischemic time, increased use of temporary mechanical circulatory support and mechanical ventilation. There was no difference in posttransplant survival at 9 months (91.1% vs. 88.9%) (p = .4). We conclude that patients with RCM/HCM have benefited from the new HT allocation system, with increased access to HT without affecting short-term posttransplant survival.

Increased frequency of heart transplantation, shortened waitlist time and preserved post-transplant survival in adults with congenital heart disease, on the new heart transplant allocation system

Historically, adult congenital patients have longer waitlist time and worse outcomes on the heart transplant waitlist as well as poorer early post-transplant survival. A new heart transplantation allocation system was implemented in the United States on October 18, 2018. The effect of the new allocation system on adult congenital patients is unknown. Adult congenital patients listed for transplantation between November 1, 2015 and September 30, 2019 registered in the United Network for Organ Sharing were included in the study. October 18, 2018 was used as the limit to distribute listed and transplanted patients into old and new groups. A total of 399 patients were listed for heart transplant only, 284 in the old system and 115 in the new system. Clinical characteristics were similar between both groups. The cumulative incidence of poor outcome on the transplant list was similar in both groups (P = .23), but the cumulative incidence of transplant was higher in the new system group (P < .009) and was associated with a shorter waitlist time. The one-year post-transplant outcome was similar between old and new groups (P = .37). The new allocation system has benefited adult congenital patients with increased cumulative frequency of transplantation without worsening short-term survival after transplantation.

Improved survival after heart transplantation in patients bridged with extracorporeal membrane oxygenation in the new allocation system

BACKGROUND

Historically, patients bridged on extracorporeal membrane oxygenation (ECMO) to heart transplantation (HT) have very high post-transplant mortality. In the new heart transplant allocation system, ECMO-supported patients have the highest priority for HT. However, data are lacking on the outcomes of these critically ill patients. We compared the waitlist and post-transplant outcomes of ECMO-supported patients in the new and old allocation systems.

METHODS

Adult patients supported by ECMO at the time of listing or transplantation who were registered in the United Network for Organ Sharing database between November 1, 2015 and September 30, 2019 were included. Clinical characteristics, outcomes in the waitlist, and post-transplant survival were compared between the old and new systems. Cox Proportional and subdistribution hazard regression models were used to evaluate the variables contributing to the post-transplant and waitlist outcomes RESULTS: A total of 296 ECMO-supported patients were listed for HT. Of these, 191 were distributed to the old system, and 105 were distributed to the new system. Patients listed in the new system had a higher cumulative incidence of HT (p < 0.001) and lower incidence of death or removal (p = 0.001) from the transplant list than patients listed in the old system. The 6-month survival after transplantation was 74.6% and 90.6% for the old- and new-era patients, respectively (p = 0.002). Among ECMO-supported patients, being listed or transplanted on the new system was independently associated with improved outcomes in the waitlist and after transplantation.

CONCLUSIONS

With the implementation of the new heart transplant allocation system, ECMO-supported patients have a shorter waitlist time, improved frequency of HT, and improved short-term post-transplant survival.

Understanding Heart Failure

Heart failure (HF) is a growing global health concern that affects more than 20 million people worldwide. With an ever-growing segment of the population over the age of 65, the prevalence of HF and its associated costs are expected to increase exponentially over the next decade. Advances in the understanding of the pathophysiology and treatment of HF have resulted in the ability to enhance both the quantity and the quality of life of patients with HF. This article reviews the current understanding of the pathophysiology, cause, classification, and treatment of HF and describes areas of uncertainty that demand future study.

Discharge outcomes in patients with paracorporeal biventricular assist devices

BACKGROUND

As waiting time for heart transplantation has increased, ventricular assist devices have become critical for "bridging" patients with end-stage heart failure. Because most reported post-discharge experience is with left ventricular assist devices (LVAD), we sought to evaluate the safety and feasibility of home discharge on paracorporeal biventricular assist devices (BIVAD).

METHODS

We retrospectively reviewed the hospital course and post-discharge outcomes of 46 consecutive patients who received paracorporeal VADs as bridge to transplant. The success of home discharge was assessed by frequency and reasons for hospital readmission and survival to transplant.

RESULTS

Thirty patients (65%) were successfully transferred from the intensive care unit and considered candidates for discharge. Of the 26 patients discharged home, 11 were supported with an LVAD and 15 with BIVADs. Median duration of support until transplant, explant, or death did not differ significantly between LVAD or BIVAD patients (91 days vs 158 days; p = 0.09). There were 26 readmissions for medical or device-related complications; 10 in 7 LVAD patients and 16 in 10 BIVAD patients, with no difference in median length of stay (17 days vs 25 days; p = 0.67). Out of hospital duration of support was similar between LVAD and BIVAD patients (61 days vs 66 days; p = 0.87) as were 6-month and 1-year event-free survival rates (p = 0.49).

CONCLUSIONS

Outcomes were similar in patients bridged to transplant on home paracorporeal BIVAD versus LVAD support. We recommend discharge for stable patients demonstrating device competency and adequate home care regardless of the need for univentricular or biventricular paracorporeal support.

Cardiac stem cells in patients with ischemic cardiomyopathy: discovery, translation, and clinical investigation

The increasing prevalence of heart failure, in the US and worldwide, poses a significant burden to patients, practitioners, and healthcare systems. Hence, there is a pressing need for alternative therapies to enhance the current treatment armamentarium. Accordingly, when considering heart failure of ischemic etiology, an intervention designed to regenerate the attending loss of myocardium could potentially result in improved cardiac function, functional status, and quality of life. Significant strides have been made by investigators in the study of stem cell therapy for cardiac repair; recently with cardiac-derived progenitor cells. These cells include cardiospheres, cardiosphere-derived cells, and c-kit positive cardiac stem cells. Herein, a review of both preclinical studies and phase I clinical trials of these cell types is presented. A detailed account of in vitro characterization, in vivo bioactivity, and safety and efficacy in humans is outlined. Thus far, encouraging results have been realized, although larger studies have yet to be undertaken.