Atrial Function and the Pressure-Strain Relationship in Patients with Fontan Circulation.

PURPOSE: Atrial function is associated with exercise tolerance and survival in patients with Fontan circulation. Although atrial function is often evaluated using strain parameters, changes in atrial pressure are also important but have not been well studied. This study aimed to investigate the atrial pressure-strain relationship in patients with Fontan circulation using data from cardiac catheterization and MRI. METHODS: We retrospectively included 16 patients (median age: 12 years) who underwent cardiac MRI between 2020 and 2026, and 10 control patients (median age: 8.5 years). Atrial strain values were evaluated from 4-chamber cine MRI images. Pulmonary artery wedge pressure waveforms were used as a surrogate for atrial pressure. The pressure-strain index was calculated as an integrated measure of atrial pressure and strain. RESULTS: The 2 groups showed no significant differences in age or body size. Patients with Fontan circulation had higher central venous pressure (CVP) and a lower cardiac index (CVP: 11.5 vs. 4.0 mmHg, P < 0.001; cardiac index: 2.9 vs. 3.8 L/min/m2, P = 0.007). Reservoir and conduit strains were lower in the Fontan group (reservoir strain: 16.7 vs. 26.2%, P < 0.001; conduit strain: 6.2 vs. 18.7%, P < 0.001); however, no significant difference was observed in pump strain between the groups. No significant difference was also noted in pressure-strain index between the 2 groups (0.2 vs. 0.2, P = 0.417). CONCLUSION: In patients with Fontan physiology, reservoir and conduit strain were lower than in controls. In contrast, atrial pressure-strain relationship was not clearly associated with conventional Fontan hemodynamic parameters. These findings suggest that the physiological significance of atrial pressure-strain relationship in the Fontan circulation remains uncertain.