Impact of Functional Warm Ischemic Time on Outcomes after DCD Heart Transplantation: A Paradigm Shift Over a Decade.

BACKGROUND: Functional warm ischemic time (FWIT) is known to affect outcomes after donation after circulatory death (DCD) heart transplantation (HTx), but its definition lacks worldwide consensus. This study examines the impact of FWIT on outcomes in DCD HTx. METHODS: This study included 125 adult DCD HTx recipients retrieved by direct procurement and perfusion (DPP), 2015-2026. FWIT was defined as the interval from donor systolic blood pressure <50 mmHg to reperfusion on ex-situ normothermic machine perfusion. Recipients were stratified by FWIT (≤30 vs >30 minutes). Primary outcomes were severe primary graft dysfunction (PGD) and all-cause mortality, modelled using restricted cubic splines (RCS) and Cox regression. RESULTS: FWIT was ≤30 minutes in 87 recipients (69.6%) and >30 minutes in 38 (30.4%), median FWIT was 27 minutes (IQR 24-32). Over a median follow-up of 5.4 years, 24 deaths occurred. FWIT was not independently associated with mortality (HR 1.11, 95% CI 0.83-1.46), RCS modelling showed no significant association across the observed range (HR 1.10 at 35 min, HR 1.13 at 40 min, vs. reference of 30 min). There was no significant difference between ≤30 and >30 min groups in survival at 1 year (88.8% vs 84.4%, p=0.75), incidence of severe PGD (23% vs 23.7%, p>0.99), post-transplant mechanical circulatory support (23% vs 31.6%, p=0.31), or long-term survival on Kaplan-Meier analysis (p=0.304). CONCLUSIONS: Prolonged FWIT does not appear to adversely affect HTx outcomes in this cohort. Larger, multicentre studies are needed to define an optimal FWIT threshold and a unified definition worldwide.