Impact of Ischemic Time on Functional Exercise Capacity after Orthotopic Heart Transplantation

Abstract

Ischemic time (IT) is an independent risk factor for patients' functional exercise capacity (FEC) during the months following orthotopic heart transplantation (OHT). The OHT recipient's post-transplant FEC, measured in peak VO2, is directly associated with improved quality of life. There is debate in the literature about the deleterious impact of extended IT on FEC following OHT. 15 OHT recipients (14 males; <3 months from OHT) performed a symptom-limited graded metabolic exercise test where peak relative VO2 was measured in an outpatient cardiac rehabilitation setting. IT was obtained from the anesthesia post-operative note. VO2 and IT values were dichotomized based on previous literature: high, ≥14 mL/kg/min (or ≥12 mL/kg/min if taking a beta blocker), and low, <14 mL/kg/min (or <12 mL/kg/min if taking a beta blocker), and short, <180 min and long, ≥180 min, respectively. Continuous variables were presented as medians and interquartile range (IQR). A Fisher's Exact Test was used to determine if extended IT is associated with a significantly decreased FEC. The minimal and maximal IT were 62 and 312 minutes, respectively. The median (IQR) recipient and donor characteristics are presented in Table 1. The Fisher's Exact Test between IT and FEC yielded a p value of 0.62. Surprisingly, extended IT was not associated with decreased FEC (<12-14 mL/kg/min) in the months following OHT in those recipients who survived to discharge with stamina sufficient to engage in outpatient cardiac rehabilitation. The wider IQR of peak VO2 in recipients with extended IT, despite the higher number of recipients, suggests that while properly selected allografts are able to tolerate a longer IT without compromising intermediate term FEC, this is not a homogenous correlation and other peri-transplant factors may modify FEC. Additional analyses will be presented including assessment of donor gender and allograft heart-rate pre- and post-transplant.