Functional Assessment and Transplantation of the Donor Heart After Circulatory Death
Messer SJ, Axell RG, Colah S, et al. J Heart Lung Transplant. 2016;35(12):1443-1452. doi: 10.1016/j.healun.2016.07.004.
Reviewers: Johann Mathews, MD1; Henry Liu, MD1
- Drexel University College of Medicine, Hahnemann University Hospital, Philadelphia, PA
There is a huge demand for donor hearts for patients waiting for heart transplantation. Most heart donors are from brain-dead donors, the number of which unfortunately is significantly fewer than the number of patients who need heart transplantation. As the demand for heart transplantation continues to increase, donation after circulatory-determined death (DCD) needs to be explored as a source of donor hearts, although the use of DCD donor hearts is still considered not safe, because currently we don’t have a reliable technique to evaluate the cardiac function of DCD donor hearts. Thus, the authors of this study described a new strategy of assessing the heart function of DCD donor hearts by using a technique called normothermic regional perfusion (NRP) to restore cardiac function. This study yielded a very good clinical program.
After exclusion of the cerebral circulation, the donor heart was perfused by NRP method. NRP restores cardiac functions. In the process of recovering myocardial contractility and weaning off NRP, cardiac output and other hemodynamic measurements, pressure-volume loop, and biventricular and valvular functions were assessed. The overall function of the heart was evaluated during 2 phases: the feasibility and the clinical phase. The Organ Care System (OCS) was put into working mode in the feasibility phase but not in the clinical phase. Hearts believed to have adequate function were chosen to proceed for transplantation.
Of the 17 potential donors, 13 were identified as suitable for transplantation. The functional warm ischemic time ranged from 12 to 25 minutes (median, 18 mins; IQR, 16–20 mins). In the feasibility phase, 2 out of the 4 donor hearts were found to be unsuitable for transplantation due to poor heart function. In the clinical phase, all 9 DCD donor hearts had adequate heart function and were transplanted and had 100% survival rate. Except for one patient, all had short ITU and hospital stays. They were discharged with no episodes of rejection. There was no significant correlation in the trends of lactate levels during NRP and OCS.
NRP seems to be a reliable technique to restore the cardiac function of DCD donor hearts, so we can evaluate the cardiac function of DCD donor hearts. We previously could only depend upon the lactate level as the marker to identify a candidate for heart transplant despite its validity having been questioned. Functional assessment of the DCD donor heart expanded the donor pool significantly to enable more patients to qualify for a heart transplant with favorable outcomes. Also, there was no correlation between arterial lactate levels and functional assessment of the donor heart using NRP. The use of NRP shortened the ischemia time compared to the direct procurement and perfusion technique, allowing for more DCD donors.
- NRP in DCD hearts circumvents the problem of increased periods of ischemic time that was seen in the direct procurement and perfusion technique.
- OCS is designed to keep organs in a warm functioning state outside of the body during transport. Can avoiding OCS improve perioperative outcomes? Heart transplantation by using adequately preserved donor hearts with OCS or with standard cold storage yields similar short-term clinical outcomes. The metabolic assessment capability of OCS needs further study.
- This procedure also raises certain ethical issues. Should permanent neurological injury be evaluated and documented before DCD? Is there a difference between withdrawing life support for DCD and active euthanasia? Proponents of DCD donors argue that irreversibility is not required for the declaration of death, which may truly raise ethical concerns.
- Donor 8 had the longest ischemic time, 146 minutes, yet had a good outcome. How significant is warm ischemic time in nonbeating heart donors for heart transplantation? Studies showed that reduction in warm ischemia time in lung, kidney, and liver transplant improved outcomes.
- The use of lactate levels to determine posttransplant outcome remains contentious. This study showed a poor correlation. Perhaps more studies are required to get a clearer picture.