Exercise capacity improves with time in pediatric heart transplant recipients

The purpose of this study was to profile the exercise capacity of pediatric heart transplant recipients over time and to identify factors associated with lower exercise capacity.

Pediatric heart transplant (HTx) recipients >6 years of age underwent annual cycle ergometry exercise testing (GXT). Exercise testing values were converted to percent predicted based on age and gender when available. Linear regression analysis adjusted for repeated measures was used to determine trends over time and associated factors.

A total of 58 patients (34 males, 59%) had 202 GXTs (2 to 8 years post-transplant). The mean percent predicted maximum heart rate (HR) response was 76 +/- 10% predicted, increased non-linearly with time post-transplant (p<0.0001), and was associated with a higher resting HR, longer time post-transplant and older age at transplant. Mean percent predicted workload was 66 +/- 15%, mildly below normal controls. Mean maximum oxygen consumption (VO(2)max) was 30 +/- 8 ml/kg/min and was found to be influenced over time by an interaction between age at transplantation and time since transplant. Greater systolic blood pressure (BP) response was associated with longer time post-transplant and higher resting systolic BP. Overall, pediatric heart transplant is associated with good exercise capacity. Younger age at transplant is associated with greater exercise capacity (VO(2)max). Serial trends in HR, BP response and VO(2)max may provide supportive evidence for graft reinnervation. Deterioration in VO(2)max was associated with graft loss because of vasculopathy.

The utility of serial routine GXT in pediatric heart transplant recipients warrants further study, especially for its role in the detection of graft vasculopathy.