Assessment of Aerobic Exercise Capacity in Fontan Survivors

Abstract

PURPOSE: To compare the exercise response of pediatric and adolescent Fontan survivors utilizing three separate cycle ergometer protocols. METHODS: We evaluated 3 Fontan cohorts, each consisting of 15 age and size matched patients, utilizing one of the following cycle ergometer protocols: James, Single Ventricle (SV) and Ramp. SV has a small and large progression of 50 or 100 kilopond-meters (kpm) every 3 minutes based on a body surface area cut point of 1.2 meters2. All tests achieved maximal effort. Total working capacity (TWC), maximal heart rate (MHR) and maximal oxygen consumption indexed for weight (MVO2) were measured. The ventilation to volume of carbon dioxide (VE/VCO2) slope was calculated for each patient. RESULTS: Subject age, height and weight were similar between groups. Exercise results are displayed in the table. The James protocol demonstrated significantly lower exercise duration (ET) and TWC. Moreover, James resulted in missing VE/VCO2 slope measures in 8 subjects (53%) compared to none for SV and Ramp. There was no difference in MVO2 and maximal respiratory quotient (MRQ) between cohorts. Ramp showed a decreased ET compared to SV and a decreased VE/VCO2 slope compared to James and SV.Table: No title available.*James vs SV, ‡James vs Ramp, !SV vs Ramp DISCUSSION: All tests achieved a maximal effort. There were no differences between the SV protocol and ramp protocols, with the exception of VE/VCO2 slope and ET. The Ramp protocol achieves the same approximate TWC with no difference in heart rate and metabolic measures with a shorter duration. The James protocol may be too aggressive for the Fontan population resulting in missing VE/VCO2 slope measures as well as shorter durations when compared to SV and Ramp. CONCLUSION: It appears that the Ramp is optimal for achieving a maximal test in Fontan survivors without loss of data or prolonged testing duration.