Perfusion system effective at preserving donor hearts
A system that keeps a heart perfused and beating outside a human body was associated with a low rate of primary graft dysfunction and could potentially extend the geographic area for heart retrieval and allow for the safe usage of hearts with non-ideal features, researchers reported at the Annual Meeting and Scientific Sessions of the International Society for Heart and Lung Transplantation.
Traditionally, after explantation, hearts are transported in a cooler of ice, and current guidelines call for an ischemic time — the time the heart is out of circulation — of no more than 4 hours, Jacob N. Schroder, MD, assistant professor of surgery at Duke University Medical Center, said during a presentation.
Partly as a result of ischemic time having to be so short, and the frequent presence of certain factors that make the donor heart not ideal, he said, 70% of consented hearts end up not being used for transplantation.
Schroder and colleagues conducted the single-arm EXPAND trial of a perfusion system (Organ Care System [OCS] Heart, TransMedics) designed to safely preserve donor hearts for longer than the traditional cooler of ice. The system for donor hearts is not yet approved for use in the United States, but a similar system for donor lungs is approved.
For the study, donor criteria included at least one of the following factors that make them extended criteria or higher risk: ischemic time > 4 hours, donor age older than 45 years, down time up to 20 minutes, hearts with left ventricular hypertrophy of 12 mm to 16 mm and hearts with nonspecific CAD, Schroder said.
The primary effectiveness endpoint was 30-day recipient survival and 24-hour freedom from primary graft dysfunction compared with a performance goal of 65%. The secondary effectiveness endpoint was percentage of donor hearts transplanted. The key safety endpoint was the rate of moderate and severe primary graft dysfunction and primary nonfunction at 30 days.
Of the 93 donor hearts placed on the OCS in the study, 81% were successfully transplanted, compared with approximately 35% using traditional methods, Schroeder said.
Mean total out-of-body time was 381 minutes (range, 173-682), mean perfusion time was 278.6 minutes and mean ischemic time was 102.1 minutes, he said.
During perfusion, mean aortic pressure was 81.2 mm Hg, mean coronary flow was 736 mL per minute and final instrumentation arterial lactate was 3.08 mmol/L, according to the researchers.
Among the 75 recipients, the mean age was 56 years, 81% were men, 69.3% were status 1A on the waitlist, 64% had a history of mechanical circulatory support, 16% were men who received a female donor heart and 14.7% had renal dysfunction.
The primary effectiveness endpoint was achieved in 88% of recipients, with 94.7% still alive at 30 days and 89.3% free from severe primary graft dysfunction at 24 hours, and results were consistent regardless of inclusion criteria, Schroder said.
At 30 days, the rate of moderate and severe primary graft dysfunction was 14.7%, of which 10.7% was severe, which is significantly lower than most published data, according to the researchers.
“The Heart EXPAND study showed that using the OCS perfusion system is safe, effective and can significantly expand our current donor pool of hearts for transplantation,” Schroder said in a press release. – by Erik Swain
Schroder JN, et al. Abstract 79. Presented at: Annual Meeting and Scientific Sessions of the International Society for Heart and Lung Transplantation; April 3-6, 2019; Orlando.
Disclosure: The study was funded by TransMedics. Cardiology Today could not confirm relevant financial disclosures for Schroder at the time of publication.