Donor Hearts Can Withstand Longer Ischemic Times

Longer allograft ischemic times didn’t have to mean worse outcomes for patients in the long run, one heart transplant program found.

Survival after transplants from 1999-2020 was similar between recipients of hearts with standard allograft ischemic times of 4 hours or less and peers getting hearts subject to extended ischemic times:

• Survival at 30 days (95.5% vs 94.9%, P=0.16)
• Survival at 1 year (81.2% vs 85.3%, P=0.90)
• Survival at 3 years (66.5% vs 67.2%, P=0.57)
• Survival at 5 years (48.9 vs 53.5%, P=0.62)

Average ischemic time in the extended-time cohort was 280 minutes compared with 195 minutes in the standard group.

Based on these data, the practice of accepting extended ischemic times appears safe, according to Brandon Guenthart, MD, of Stanford University in California, reporting at the Society of Thoracic Surgeons virtual meeting.

Longer times may reflect travel due to the transport of donor hearts across longer geographical distances. Guenthart noted that the rise in long-distance procurement at Stanford from 2017 to 2021 was accompanied by a trend of more organs being offered to status 4+ patients, or people lower down the transplant waitlist.

Four hours is the commonly accepted limit of cold ischemic time at most transplant centers. It has been thought that longer times contribute to allograft dysfunction and worse patient survival after transplant. Yet there are several case series reporting equivalent long-term results with extended ischemic periods — perhaps at the expense of greater early morbidity and resource utilization in the first 30 days, according to Guenthart.

His group found the standard and extended-time groups to share a similar risk of post-operative stroke and similar needs for post-operative venoarterial extracorporeal membrane oxygenation, intra-aortic balloon pumps, and dialysis. Graft rejection rates approached 8% for both groups at 1 year.

“Certainly, I think every case is individualized and donor and recipient characteristics need to be considered … Time is really only one variable — myocardial protection, transport conditions, surgical technique, limiting warm ischemia may have greater impact and require further investigation,” he told the audience.

The retrospective cohort study counted 735 consecutive adults who underwent heart transplant at Stanford, excluding multi-organ transplants and re-transplantation. Of these, 266 were in the extended-time group.

Transplant recipients had a mean age around 52 years and donors averaged 33 years of age. Over 70% of both the donor and recipient groups were men. Characteristics were similar between the standard- and extended-time groups.

The study sample was too small to analyze the outcomes of patients with ischemic times over 6 hours or those with various blood types, Guenthart acknowledged.

He noted that since the time of this analysis, Stanford has started using the SherpaPak cold preservation system to transport donor hearts in most cases, regardless of donor age or distance.

He warned that reporting of ischemic times will get more complex given greater adoption of donation after circulatory death procurement and the TransMedics Organ Care System, as operators can count on multiple periods of warm and cold ischemia and normothermic perfusion.

Total preservation time would be an important metric to track going forward, the researcher suggested.

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