The cardiac surgeon perspective—cardiac transplantation following donation after circulatory death: expanding the donor pool

The number of heart transplants performed in the United States annually continues to increase, reaching over 4,000 in 2022. This increase was mostly driven by the 68% increase in the use of donation after circulatory death (DCD) donors with a smaller increase of 4.6% in donation after brain death (DBD) donors (1). Some of this increase is also related to liberalization of qualifications of potential recipients, such as increased age and comorbidities that were previously prohibitive [human immunodeficiency virus (HIV), hepatitis C] but now are treatable. Meanwhile, implantations of durable left ventricular assist devices (LVADs) continue to decline (1,2). Altogether, despite increases in heart transplantation, the current incidence of surgical treatment of end-stage heart failure does not meet the need of patients suffering from advanced heart failure.

While DCD donor use is becoming more prevalent, several limitations limit widespread adoption and standardization. First, the method of procurement is essentially evolving into two camps: (I) normothermic regional perfusion (NRP) and (II) direct procurement and perfusion (DPP). At the current time, no difference in outcomes has been demonstrated between these two methods (3). DPP currently requires use of the Organ Care System (OCS) Heart (Transmedics, Inc., Andover, MA, USA), a portable, normothermic perfusion device, which is currently the only U.S. Food and Drug Administration (FDA) approved extracorporeal perfusion device. In the prospective, randomized EXPAND trial, there was no significant difference in 1-year survival between DCD donors using the OCS Heart, and DBD donors preserved with traditional cold storage (4). Currently, the OCS Heart can no longer be bought by individual programs, and TransMedics, Inc. has developed their own procurement company, the National OCS Program, that must be utilized in order to use the OCS Heart system. While this does offer some advantages including reduced use of an institution’s own personnel, programs have to give up control of the procurement to an unknown entity, and the cost may be prohibitive to small and medium volume programs. NRP, on the other hand, requires more personnel resources from one’s own institution, which again may be difficult for small to medium size programs, but keeps control of the procurement with the implanting team and is less costly than DPP. An additional advantage of NRP is the ability to assess the donor heart in real time rather than relying solely on lactate measurements from the OCS technology.

Recent advancements in cold storage technology have also bolstered outcomes with DCD heart transplant. The SherpaPak Cardiac Transport System (Paragonix Technologies, Inc., Waltham, MA, USA) has demonstrated a decreased incidence of primary graft dysfunction (PGD) (5) and reduced use of post-transplant mechanical circulatory support (6) compared to traditional ice cold storage, which has emboldened programs to push the limits of distance that they are willing to travel. The longest reported ischemic time currently is 7.5 hours with a distance of over 2,500 nautical miles in a DBD donor (7). A recent subanalysis of the GUARDIAN heart registry has also demonstrated that use of the SherpaPak for extended criteria DBD hearts reduced PGD rates with lower use of post-transplant mechanical circulatory support (8). These results could potentially be extrapolated to DCD, but further analysis and data acquisition will be required to determine the benefits of the SherpaPak in conjunction with DCD donor hearts. Another new preservation system is the XVIVO Heart Assist Transport (XHAT) system that has the potential to extend ischemic time even further. This technology utilizes an ex vivo, hypothermic perfusion system for the heart that has so far demonstrated acceptable post-transplant outcomes with ischemic times beyond 10 hours (9). The XHAT trial was recently approved by the U.S. Federal Drug Administration to include DCD heart transplants, and patient accrual is ongoing for the clinical trial, “Prospective, Multi-center, Single-Arm, Open-Label Study of Hearts Transplanted after Non-Ischemic Heart PRESERVation from Extended Donors”. This device has the potential to supplant other perfusing preservation devices, but we will need to wait for the results of the trial.

In summary, the use of DCD donors for heart transplant continues to grow but much is still to be determined in relation to best methods and mid to long term outcomes. What is clear is that heart transplant programs will need to use DCD hearts to stay relevant in the current era of heart transplantation. As more DCD heart transplants are performed and with the addition of new centers utilizing DCD donors, it is imperative that we are transparent about our methods and outcomes in order to provide heart transplant patients with the best possible outcome. More experience and ongoing analysis of the current clinical outcomes will help determine the specific direction that DCD heart transplant takes in the United States.

Acknowledgments

Funding: None.

Footnote

Conflicts of Interest: The authors have no conflicts of interest to declare.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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