Abstract 13444: Impact of Oral Vitamin C on Endothelial Function and Exercise Performance in Children and Young Adults with Fontan Circulation
Background: Fontan-palliated children and young adults demonstrate evidence of endothelial dysfunction, secondary to vascular oxidative stress. Medical therapy that is capable of restoring normal endothelial function may lead to improved functional health status.
Objective: To evaluate the impact of the antioxidant vitamin C on endothelial function and exercise performance in Fontan-palliated patients.
Methods: We performed a randomized, double-blind, placebo-controlled trial of oral vitamin C in children and young adults with Fontan circulation. Vitamin C dosing was standardized for age, based upon tolerable upper intake levels. Peripheral vascular function, as measured with digital pulse amplitude testing (EndoPAT), and exercise capacity were assessed prior to, and after, 4 weeks of study drug treatment. Primary outcome measures included the EndoPAT index and peripheral arterial tomography (PAT) ratio, both validated markers of vascular function. Secondary outcome measures included peak oxygen consumption and work. Analysis of covariance, adjusting for baseline values, was conducted to examine the treatment effects on each outcome variable.
Results: Fifty-three subjects were enrolled and randomized; 23 vitamin C- and 21 placebo-assigned subjects completed the protocol (83% overall). Median age was 15 years (IQR 11.7 - 18.2) and median time from Fontan completion was 11.9 years (9.0 - 15.7). Right ventricular morphology was dominant in 30 (57%). There were no baseline differences between groups in the primary or secondary outcome measures. Among all subjects, vitamin C therapy was not associated with a statistical improvement in either the primary or secondary outcome measures. In a subgroup analysis of subjects with abnormal vascular function measures at baseline (below 25%’ile in normal controls), compared with placebo, vitamin C therapy more frequently resulted in normalization of the EndoPAT index (5/11 (45%) vs. 1/6 subjects (17%)) and PAT ratio (5/13 (38%) vs. 1/8 subjects (13%)).
Conclusions: Vitamin C appears to improve endothelial function in Fontan-palliated children and young adults with abnormal markers of vascular function. We speculate that enhanced vascular health may result in improved functional health status.
- © 2011 by American Heart Association, Inc.