Exercise capacity and cardiac allograft ischemic time in recent heart transplant recipients

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 (EC), is not fully understood. This prospective, observational cohort study aimed to determine the association between EC, a strong predictor for post-transplant survival, and relatively longer IT.

Thirty heart transplant recipients were grouped dichotomously according to relatively longer (>180 minutes) or shorter (≤180 minutes) IT. A cardiopulmonary exercise test (CPET) was performed post-transplant upon cardiac rehabilitation admission, during which EC [peak volume of oxygen consumption (VO₂)] and CPET duration were measured and compared between groups.

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 United Network for Organ Sharing 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, ratings of perceived exertion, protocol performed, and EC.

In this modest-sized cohort, EC was higher in heart transplant recipients with donor IT >180 minutes compared with those with IT ≤180 minutes. However, CPET duration was significantly shorter in those with relatively longer IT.