Peak oxygen consumption (pVO2) measured by cardiopulmonary exercise test (CPET) predicts mortality in adults with a Fontan circulation. The purpose of this study was to assess the additive prognostic value of change in pVO2 over time.Methods
We analyzed a cohort of adults (≥18 years old) with a Fontan circulation who underwent at least 2 maximal CPETs separated by 6-30 months at Boston Children's Hospital between 2000 and 2015. Survival analysis was performed to determine whether changes in CPET variables, including pVO2 between consecutive tests, were associated with subsequent clinical events. The primary outcome was transplant-free survival.Results
The study included 130 patients with 287 CPET test pairs. Average age was 26.6 ± 9.5 years. Baseline pVO2 averaged 22.0 ± 5.7 mL/kg/min or 60.9% ± 13.7% predicted. In the cohort overall, there was no change in mean pVO2 between sequential CPETs. Eleven patients died and 2 underwent transplant. On average, pVO2 declined for patients who subsequently died or underwent transplant but remained stable among those who did not (−9.8% ± 14.6% vs 0.0 ± 13.0%, P < .01). Those with a decline in pVO2 between CPETs were at greater risk of death or transplantation (per 10% decrease in pVO2: HR = 2.0, 95% CI 1.2-3.1, P = .004). Change in pVO2 remained a significant predictor of death or transplant after adjusting for pVO2 at first CPET (per 10% decline in pVO2: HR = 2.5, 95% CI 1.5-4.2, P < .001).Conclusions
A decline in pVO2 between consecutive CPETs predicts increased risk for death or transplant in adults with a Fontan circulation independent of baseline pVO2. These results support the additive clinical value of serial CPET in this population.