Exercise Capacity and Cardiac Allograft Ischemic Time in Recent Heart Transplant Recipients

Background Prolonged ischemic times (IT) for transplant hearts transported under cold storage conditions are associated with an increased risk of mortality, however the impact of IT on functional outcomes, such as exercise capacity, is not fully understood. This prospective, observational cohort study aimed to determine the association between exercise capacity, a strong predictor for post-transplant survival, and relatively longer IT. Methods Thirty heart transplant recipients were grouped dichotomously according to relatively longer (>180 min) or shorter (≤180 min) IT. A cardiopulmonary exercise test (CPET) was performed post-transplant upon entry into cardiac rehabilitation, during which peak VO2 was measured using a metabolic cart. CPET variables, including exercise capacity and test duration, were compared between groups. Results This cohort was predominantly male (n=22, 73%) with a median age of 57.5 years [Q1-Q3: 54.0 - 65.0]). Baseline demographics and characteristics were similar between groups aside from UNOS listing status, in which patients listed as Status 1 or 2 were more likely to have long IT. Twelve (40%) participants received a donor heart with long IT. Surprisingly, higher peak VO2 was observed in those with long (15.0±2.8) than short (13.1±3.7) IT (p=0.009). However, CPET duration was significantly shorter in recipients with a long IT (6.3 vs. 7.7 minutes, p=0.048) despite similar time since transplant, rate of perceived exertion, protocol performed, and exercise capacity. Conclusions In this modest-sized cohort, exercise capacity was higher in heart transplant recipients with donor IT >180 minutes compared to those with IT ≤180 minutes. However, exercise duration was significantly shorter in those with relatively longer IT.