Prognostic value of exercise testing during heart transplant evaluation in children

Background-Maximum oxygen consumption (peak VO₂) <50% predicted on exercise testing is a class I indication for heart transplant (HT) listing in children. This recommendation is based on exercise data in adults. We assessed the association of peak VO₂<50% predicted during HT evaluation with freedom from death or deterioration in children. Methods and Results-We analyzed all children who underwent exercise testing during HT evaluation at our center between 2002 and 2011. Patients with peak VO ₂<50% predicted were compared with those with peak VO ₂≥50% predicted for the composite outcome of death before HT, initiation of mechanical circulatory support, and HT at highest urgency status, using time-to-event analyses. There were 50 children in the study (median age, 15 years; interquartile range, 13-17 years; 24 girls; 18 with palliated single ventricle). Overall, 24 children reached the composite end point. Peak VO ₂<50% predicted was associated with outcome in children with biventricular circulation (hazard ratio, 4.7; 95% confidence interval, 1.8-12.3; P<0.001) but not in those with a palliated single ventricle (hazard ratio, 1.3; 95% confidence interval, 0.1-12.0; P=0.80). Similarly, VE/VCO₂ slope ≥34 was associated with outcome in children with biventricular circulation (hazard ratio, 2.7; 95% confidence interval, 1.1-7.1; P<0.001) but not in children with a palliated single ventricle. Conclusions-Exercise testing during HT evaluation in children with biventricular circulation identified those at higher risk of death or deterioration in this small study. Larger studies are needed to assess the role of exercise testing during HT evaluation in children with a palliated single ventricle.