- Researchers sought to analyze whether heart transplant outcomes hinged on the temperature setting of static cold storage of the donor heart.
- Between 4-8°C and 10°C cold preservation, there was a marked difference in graft and survival outcomes across adult heart transplants at two high-volume centers.
- The study adds evidence that preservation temperature may play a critical role in early graft performance, as cold static storage has been linked to protein denaturation, conduction-system injury, and irreversible diastolic dysfunction.
Colder was not better when it came to donor heart storage, according to preliminary findings from a retrospective analysis.
Between static cold storage (SCS) at 4-8°C and 10°C, there was a marked difference in outcomes across adult heart transplants performed at two high-volume centers in the U.S., reported a team led by Aaron Williams, MD, of Vanderbilt University Medical Center in Nashville, Tennessee, in Circulation: Heart Failure.
After propensity score matching, 10°C preservation was associated with less primary graft dysfunction (PGD; 2.9% vs 14.6%, P=0.008), less post-bypass left (10.1% vs 37.7%, P<0.001) and right ventricular dysfunction (0% vs 10%, P=0.003), reduced new intra-aortic balloon pump use (2.9% vs 22.3%, P<0.001), and improved 1-year survival (95.7% vs 86.2%, P=0.046).
These favorable outcomes emerged despite the 10°C-preservation transplants being associated with objectively higher donor and recipient risk features, including older age for both the recipient and the donor, greater donor-recipient sex mismatch, more frequent donor undersizing, and a higher prevalence of redo sternotomy.
“In conclusion, preservation of cardiac allografts at 10°C compared with 4-8°C SCS may yield superior early graft function posttransplant, suggesting that 10°C may provide greater myocardial tolerance to ischemia and other insults. Although these findings support the potential of 10°C preservation, additional studies directly comparing these forms of SCS are needed to determine the optimal donor heart preservation temperature,” wrote Williams and colleagues.
Theirs is the first study to compare adult heart transplant outcomes using allografts preserved at two controlled temperatures — another step in the shift away from topical ice and 4°C crystalloid storage to commercial cold preservation systems.
“For most of the modern era of heart transplantation, donor heart preservation has been governed by a single, almost reflexive principle: colder is safer,” recalled Yuliya Tipograf, MD, and Monica Colvin, MD, MS, both of University of Michigan Health in Ann Arbor. “Cold static storage, however, has been linked to protein denaturation, conduction-system injury, and irreversible diastolic dysfunction, the same injuries that render a marginal heart unusable.”
“The recognition that hypothermia is at once protective and injurious has driven a search for a preservation temperature that buys ischemic time without freezing the myocardium,” the duo explained in an accompanying editorial.
Early evidence for 10°C SCS had come from the donor lung allograft literature, where a randomized trial is already underway. The available data suggest improved lung quality and extended preservation times; researchers hope these findings can be replicated with donor hearts.
“A modest reduction in early graft dysfunction applied across an entire program would be clinically meaningful, and a wider ischemic-time window could extend the geographic reach of hearts that are now declined for distance alone,” Tipograf and Colvin commented.
Williams and colleagues had performed a retrospective analysis of all single-organ, donation-after-brain-death adult heart transplants performed at two high-volume centers, Vanderbilt and Duke University in Durham, North Carolina.
Included were 365 heart transplant recipients from 2020 to 2025 (median age 56 years, 32.1% women). The cohort was split between the 113 recipients of cardiac allografts preserved using 10°C SCS (Traferox) and 252 peers who received allografts preserved at 4-8°C SCS (Paragonix SherpaPak).
Multiorgan and adult congenital transplants were excluded, as were hearts donated after circulatory death.
Some outcomes, including cardiac indices and posttransplant length of stay, were not significantly different between temperature groups.
One “critical limitation” of the study, according to Tipograf and Colvin, was that nearly all 10°C cases were performed at Vanderbilt after its 2023 transition to that method, while nearly all 4-8°C cases were performed at Duke. “Propensity matching can balance measured donor and recipient characteristics, but it cannot disentangle a few degrees of storage temperature from differences in surgical technique, perioperative protocol, recipient selection, and the secular improvements in care that accompany any single-center transition over time.”
Study authors also acknowledged that the retrospective, observational study may have unmeasured confounders, stressing the need for a randomized trial.
“A multicenter, non-industry randomized comparison of 10°C and 4°C to 8°C storage, stratified by center and ischemic time and powered for severe PGD, would isolate the effect of temperature from the center-level factors that confound the present analysis,” the editorialists suggested.
“Until that trial is completed, the work of Williams and colleagues provides a sound rationale for 10°C preservation and gives the field a well-defined, eminently testable question for one of the few preservation variables that any program could change tomorrow,” Tipograf and Colvin concluded.
