# Double whammy: increased severe primary graft dysfunction after prolonged warm ischemia and inadequate oxygen delivery during heart transplant

## TL;DR

This study shows that both prolonged warm ischemia and poor oxygen delivery during heart transplants increase the risk of severe heart failure and death in patients.

## Contribution

The study identifies a combined effect of warm ischemia time and oxygen delivery on post-transplant outcomes in DCD heart transplants.

## Key findings

- High warm ischemic time and low oxygen delivery were linked to higher rates of severe primary graft dysfunction.
- Low oxygen delivery during transplants was associated with increased 30-day mortality.
- Oxygen delivery above certain thresholds improved outcomes despite warm ischemia.

## Abstract

This exploratory study examined the relationship between oxygen delivery index (DO2i) during DCD heart transplant (HT), warm ischemic time, and posttransplant outcomes.

All DCD HT between 10/2021 and 12/2024 using normothermic regional perfusion (NRP) at our institution were included. Multiorgan transplants and congenital heart disease patients were excluded. Critical areas—sum of magnitude and duration of DO2i under specific thresholds—were calculated for thresholds 300, 280, and 260 mL/min/m2. Receiver operating characteristics (ROC) analysis dichotomized the critical area into high area (low DO2i) and low area (high DO2i) groups. Patients were then stratified into 4 groups based on high/low functional warm ischemic time (FWIT), and high/low DO2i. Outcomes were compared across groups.

The critical area under 260 mL/min/m2 was the best predictor of severe primary graft dysfunction (PGD). 102 patients met inclusion criteria, and were stratified into four groups based on FWIT above/below 23 min and critical area below/above 1,424 mL/m2 (identified by ROC analysis). 39 (38.2%) patients had low FWIT/ high DO2i, 18 (17.6%) had low FWIT/ low DO2i, 24 (23.5%) had high FWIT/high DO2i, and 21 (20.6%) had high FWIT/low DO2i. Rates of severe PGD were greater in the high FWIT/low DO2i group compared to the low FWIT/high DO2i group (23.8% vs. 0%, p = 0.004). Rates of 30-day mortality were higher in the high FWIT/low DO2i group compared to the low FWIT/high DO2i group (14.3% vs. 0%, p = 0.039).

Higher oxygen delivery during HT was associated with improved short-term outcomes, and may counteract the myocardial damage from warm ischemia during DCD.