When is the right time for Fontan conversion? The role of cardiopulmonary exercise test

Background To determine if Fontan conversion (FC) resulted in improvement in exercise capacity (EC), and to determine the role of cardiopulmonary exercise test (CPET) in risk stratification of patients undergoing FC. Methods A retrospective review of patients who underwent CPET prior to FC at Mayo Clinic from 1994 to 2014. The patients who also underwent post-operative CPET were selected for the analysis of improvement in EC defined as 10% increase in baseline peak oxygen consumption (VO₂). Results 75 patients CPET prior to FC; mean age 24 ± 6 years; 44 males (59%); and 51 (68%) were in NYHA III/IV prior to FC. Pre-operative peak VO₂ was 15.5 ± 3.4 ml/kg/min. A comparison of pre- and post-FC CPET data was performed using 42 patients (56%) that underwent CPET after FC. Improvement in EC occurred in 18 of 42 patients (43%). Baseline peak VO₂ > 14 ml/kg/min was associated with improved EC (hazard ratio [HR] 1.85; P = .02). Improvement in New York Heart Association (NYHA) class occurred in 12 (67%) patients with improved EC vs 2 (8%) without improved EC. Improvement in NYHA class was more likely to occur in patients with improved EC compared to those without improvement EC (odds ratio 4.11, P = .01). There were 10 (13%) perioperative deaths, and baseline peak VO₂ ≤ 14 ml/kg/min was predictive of perioperative mortality (HR 3.74; P < .001). Conclusions Baseline peak VO₂ was predictive of perioperative survival, and improvement in EC. Performance on CPET in failing Fontan patients might be a useful clinical parameter in determining appropriate timing of FC.