Abstract 17026: Predictors of Exercise Performance in Pediatric Heart Transplant Recipients

Abstract

Introduction: Previous studies have shown that peak oxygen consumption (VO 2 ) is impaired in pediatric heart transplant (HT) recipients compared to healthy controls. This impairment in exercise performance is variable among patients, however. Research Question: What are the predictors of exercise performance in pediatric HT recipients? Aim: To assess the association of demographic (age at HT, sex, BMI, diagnosis, duration since HT), echocardiographic (LV volume z-scores, ejection fraction), hemodynamic (cardiac index, filling pressures), hematologic (hematocrit) and pulmonary (FEV1, FVC) factors with percent predicted peak (ppp) VO 2 in pediatric HT recipients. Methods : The first cardiopulmonary exercise test (CPET) performed in each HT recipient at our institution from 2003-2021 was assessed. Imaging, catheterization, and laboratory data closest in time to CPET were used. A multivariable linear regression model was developed to assess independent predictors of pppVO 2 . Results: Of 154 patients studied, 46% were female, age at HT was 9.6 ± 6 years, age at CPET was 15.4 ± 4.9 years, and time since HT was 5.8 ± 4.4 years. LV ejection fraction was 60 ±10%, pulmonary capillary wedge pressure was 12 ±4mmHg, FVC was 81 ±20% predicted, and mean pppVO 2 was 70 ± 18%. Multivariable analysis showed the age at transplant (β=-3.02/year, p<0.001) and duration since HT (β=-2.4/year, p=0.02) were significantly associated with pppVO 2. No other clinical factors were significantly associated with pppVO 2 . Variability in pppVO2 among patients was mostly explained by the variability in ppp O2 pulse (Pearson correlation coefficient, r=0.88) and surprisingly, much less by variation in ppp heart rate (r=0.3). Conclusions: Older age at HT and longer duration since HT are both independently associated with lower pppVO 2 among pediatric HT recipients whereas all other clinical factors were not. Further research is warranted to explore changes in exercise performance in this patient population longitudinally. The stronger mechanistic correlate with ppp O2 pulse (surrogate for stroke volume) rather than with ppp heart rate suggests that interventions such as rehabilitation/exercise training may improve exercise performance in pediatric HT recipients.