Pulmonary artery size is associated with functional clinical status in the Fontan circulation

Objective: In the Fontan circulation, non-pulsatile pulmonary blood flow is suggested to negatively affect pulmonary artery growth. The pulmonary vasculature is regarded a key determinant of outcome after Fontan completion. We hypothesised that in Fontan patients pulmonary artery size correlates with follow-up and functional clinical status. Methods: This is a single-centre, cross-sectional cohort study. Thirty-nine paediatric and adult Fontan patients with a concomitant cardiac magnetic resonance (CMR) scan and a cardiopulmonary exercise test between 2012 and 2013 were included. CMR-derived left and right pulmonary artery cross-sectional areas were expressed as Nakata index. Functional status was defined as peak oxygen consumption (pVO2) indexed for weight, as percentage of predicted (pred) and as New York Heart Association Functional Class (NYHA-FC). Results: Age at CMR was 18±7.2 years. Time since Fontan completion was 11.9±7.4 years. Nakata index was lower versus the reference values (238.6±78.5 vs 330±30 mm2/m2, p<0.001). Nakata index correlated negatively with age at CMR (r=-0.393, p=0.013) and time since Fontan completion (r=-0.341, p=0.034). pVO2 was 27.9±8.9 mL/min/kg and pVO2pred was 58.1%±14.1%. Nakata index correlated positively with pVO2 (r=0.468, p=0.003) and pVO2pred (r=0.353, p=0.028). Nakata index correlated negatively with NYHA-FC (r=-0.450, p=0.004). Nakata index was an independent predictor (β=0.359, p=0.007) for pVO2 (adjusted R2=0.442, with maximum heart rate and oxygen pulse at peak exercise). Conclusions: Pulmonary artery size expressed as Nakata index is a novel independent predictor for functional clinical status. Nakata index negatively correlated with follow-up duration, suggesting that chronic abnormal non-pulsatile pulmonary blood flow plays a role in lagging pulmonary arterial growth in the Fontan circulation