Abstract 14404: The Fontan Udenafil Exercise Longitudinal Trial Subgroup Analysis

Background: The Pediatric Heart Network’s Fontan Udenafil Exercise Longitudinal (FUEL) Trial (Mezzion Pharma Co. Ltd., NCT 02741115) demonstrated improvements in exercise capacity and ventricular performance following six months of treatment with udenafil (87.5 mg twice daily). In this analysis we evaluated whether subgroups within the population experienced a differential effect on exercise performance in response to treatment. Methods: The effect of udenafil on exercise was evaluated within subgroups defined by gender, race, ventricular morphology, and baseline peak oxygen consumption (VO 2 ). Linear regression modeling evaluated for differential response to udenafil (interaction of subgroup with treatment arm). Individual subgroups were excluded if the number of participants was Results: Subgroup analyses demonstrated qualitative improvements in peak VO 2 , work rate at the ventilatory anaerobic threshold (VAT), VO 2 at VAT, and ventilatory efficiency (VE/VCO 2 ) for those randomized to udenafil compared to placebo in all subgroups (Table). There was not a differential response to udenafil based on gender, race, ventricular morphology, or baseline peak VO 2 , although participants in the lowest tertile of baseline peak VO 2 and those with single left ventricles trended toward larger improvements. Conclusion: The relatively uniform improvement among subgroups in response to treatment with udenafil is consistent with the findings from the primary analysis of the FUEL trial. While the absence of a statistically significant differential effect between subgroups suggests that the effect of udenafil may not be gender, race, or morphology specific, and may not vary based on baseline exercise performance, the possibility of a larger improvements in those with poor baseline peak VO 2 and those with single left ventricle warrants further investigation.