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.

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.

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).

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.