No abstract

In Fontan patients, maximal aerobic capacity is reduced compared with healthy subjects, with better preservation of submaximal performance. Higher O(2) pulse is associated with better exercise performance, whereas adolescence and male gender are associated with decreased performance compared with healthy subjects.

Background Children and young adults with single ventricle physiology have abnormal exercise capacity after Fontan operation. A medication capable of decreasing pulmonary vascular resistance should allow for improved cardiac filling and improved exercise capacity. Methods and Results This study was a double-blind, placebo-controlled, crossover trial conducted in children and young adults after Fontan. Subjects were randomized to receive placebo or sildenafil (20 mg tid) for 6 weeks. After a 6-week washout, subjects crossed over for an additional 6 weeks. Each subject underwent an exercise stress test at the start and finish of each phase. Following sildenafil subjects had a significantly decreased respiratory rate and decreased minute ventilation at peak exercise. At the anaerobic threshold subjects had significantly decreased ventilatory equivalents of carbon dioxide. There was no change in oxygen consumption during peak exercise although there was a suggestion of improved oxygen consumption at the anaerobic threshold. Improvement at the anaerobic threshold was limited to the subgroup with single left or mixed ventricular morphology and to the subgroup with baseline serum brain natriuretic peptide levels ≥ 100 pg/ml. Conclusion In this cohort, sildenafil significantly improved ventilatory efficiency during peak and sub-maximal exercise. There was also a suggestion of improved oxygen consumption at the anaerobic threshold in two subgroups. These findings suggest that sildenafil may be an important agent to improve exercise performance in children and young adults with single ventricle physiology following Fontan operation.