Fontan pathway diameter in adults undergoing exercise catheterization: Association with hemodynamics, exercise...

The Fontan pathway (inferior vena cava-pulmonary artery connection) regulates forward flow and backward pressure, but its optimal size remains uncertain. This study aimed to evaluate the relationship between Fontan pathway diameter, hemodynamics, exercise capacity, and liver disease markers.

A retrospective review of 67 adults with extracardiac conduit (EC) or lateral tunnel (LT) Fontan procedures who underwent exercise cardiac catheterization was conducted. Minimal pathway diameter was measured via angiography or computed tomography. Exercise capacity was assessed by percent predicted peak oxygen consumption. Liver disease markers included aspartate aminotransferase-to-platelet ratio, fibrosis-4, and Model for End-Stage Liver Disease excluding international normalized ratio scores.

The mean age at catheterization was 30.4 ± 7.9 years. Minimal pathway diameter was 17.5 ± 6.0 mm. Larger diameter was associated with reduced augmentation of pulmonary and systemic blood flow during exercise (pulmonary flow, -2.3% per mm; 95% CI, -3.9 to -0.7; P = .005; systemic flow, -2.2% per mm; 95% CI, -4.1 to -0.2; P = .03), and lower percent predicted peak oxygen consumption (-0.8% per mm; 95% CI, -1.4 to -0.2; P = .009), independent of exercise mean pulmonary artery and pulmonary artery wedge pressures, and peak heart rate. No consistent association was observed between pathway diameter and markers of liver disease. Notably, the pressure gradient on the liver imposed by the pathway contributed minimally to inferior vena cava pressure at rest (0; interquartile range, 0-7.1%) or during exercise (6.4%; interquartile range, 0.5%-14.3%).

Larger Fontan pathway diameter was paradoxically associated with impaired flow augmentation during exercise, which may contribute to reduced exercise capacity.