Authors: Kaitlin M. Flannery, MD, MPH - Stanford University AND Manchula Navaratnam, MBChB - Stanford University
A 13-year-old, 30 kg, female with hypoplastic left heart syndrome palliated to an extracardiac Fontan with failing Fontan physiology has been listed for heart transplantation. She is highly sensitized resulting in limited compatible donor offers. An acceptable offer becomes available from a 32 kg donor, but the travel time is anticipated to be seven hours. What factor MOST LIKELY limits the use of Organ Care System (OCS) [TransMedics, Andover, MA] preservation in this case?
EXPLANATION
Heart transplantation is the gold-standard treatment for pediatric patients with end-stage heart failure. Due to the scarcity of acceptable donor organs, pediatric waitlist mortality remains at 20%. In the United States, an estimated 50% of potential pediatric donor hearts are not utilized, in part because of the limitations with static cold storage preservation. Prior studies have shown increased graft failure and mortality when cold ischemic time exceeds four hours, limiting the geographic distance from which organs can be accepted. Cold storage also does not permit assessment or optimization of organs, a key factor when considering donation after circulatory death (DCD).1
The Organ Care System (OCS Heart) [TransMedics, Andover, MA] is a portable ex situ perfusion, preservation, and monitoring system. The OCS delivers oxygenated, heated donor blood in a pulsatile fashion, through a cannula placed in the donor aorta, perfusing the myocardium via the coronary arteries. Blood returning to the right heart through the coronary sinus is drained back to the OCS reservoir via a cannula placed in the donor pulmonary artery. The OCS continuously monitors mean aortic pressure, coronary blood flow, and arterial and venous lactate levels.2
A randomized control trial in adult patients compared risk-adjusted six-month survival between recipients of DCD donor hearts preserved with OCS versus those preserved with traditional cold storage following donation after brain death (DBD). Risk-adjusted six-month survival was 94% in the OCS group compared with 90% in the control group. This demonstrated non-inferiority of DCD heart transplantation using OCS preservation and led to FDA approval of OCS Heart for adult patients in 2022.3
A prospective study evaluated outcomes of extended criteria donor (ECD) organs preserved with OCS following DBD. Due to concerns for poor outcomes of ECD organs preserved with static cold storage, this was not a randomized control trial. Criteria for ECD include donors ≥55 years old, donors 45-55 years old without a coronary angiogram, anticipated cold ischemic time ≥4 hours, or donors with ≥20 minutes of downtime but stable hemodynamics at procurement. Organs were accepted for transplantation if OCS monitoring demonstrated a downward-trending arterial lactate <5 mmol/L, stable aortic pressures and coronary flow, and surgeon approval. Of 173 hearts placed on the OCS, 150 were transplanted, yielding an 87% utilization rate. These organs had been declined an average of 51 times before acceptance, suggesting they would likely have been discarded without OCS preservation and assessment. The study’s primary endpoints – 30-day survival and incidence of severe primary graft dysfunction -were 96.6% and 6.7%, respectively.4
The first report of pediatric heart transplantation using OCS preservation, was published in 2025 by Duke University Medical Center. Donor weight had to be ≥40 kg to ensure system compatibility. Outcomes of eight recipients were described. The median recipient age was 13 years (range 9-18) and median weight was 58 kg (range 33-127). At the time of transplant offer, two patients were outpatient on ventricular assist device (VAD) support, while six were inpatient (three on VADs and one on ECMO). Of the organs accepted, six were from DBD donors and two from DCD donors. The median OCS duration was 273 minutes (4.5 hours), with an average arterial lactate of 2.42 mmol/L. Post-operatively, one patient required intra-aortic balloon pump support for one day and one patient required ECMO for three days. All patients survived and demonstrated normal left ventricular systolic function at hospital discharge. Hospital courses, however, were prolonged, with an average ICU stay of 34 days (range 4-101) and hospital stay of 72 days (13-249).1
OCS Heart is currently FDA approved for preservation of DCD and ECD DBD hearts in adults. Donors must be ≥40 kg to ensure system compatibility. Contraindications to OCS use include moderate to severe aortic insufficiency, visible donor-organ bruising, and known atrial or ventricular septal defects in the donor heart.2 Expanded OCS use in pediatric transplantation may be valuable for patients with complex congenital heart disease, such as Fontan physiology, who have limited compatible donor offers and often require prolonged operative times. Current OCS device size limitations remain a barrier for smaller donors.
Recipient weight of 30kg would not be an absolute contraindication to OCS use for the donor organ, as long as there would not be resultant donor-recipient size mismatch. That would be determined by the transplanting center and the specified donor size range for the patient that is listed for transplant.
Organ travel time of seven hours would not be a contraindication and often would be considered an indication for use of OCS.
REFERENCES
1. Medina CK, Aykut B, Parker LE, et al. Early single-center experience with an ex vivo organ care system in pediatric heart transplantation. J Heart Lung Transplant. 2025 Apr;4(4):545-9.
2. FDA. Organ Care System (OCS) Heart System – P180051/S001. US Food & Drug Administration. Published April 27, 2022. Accessed September 8, 2025. https://www.fda.gov/medical-devices/recently-approved-devices/organ-care-system-ocs-heart-system-p180051s001.
3. Schroder JN, Patel CB, DeVore AD, et al. Transplantation outcomes with donor hearts after circulatory death. N Engl J Med. 2023 Jun 8;388(23):2121-31.
4. Schroder JN, Patel CB, DeVore AD, et al. Increasing utilization of extended criteria donor hearts for transplantation: the OCS Heart EXPAND trial. JACC Heart Fail. 2024 Mar;12(3):438-47.
