Measuring Atrioventricular Valve Regurgitation Using 4D Flow Cardiovascular Magnetic Resonance Post-Fontan.

Atrioventricular valve regurgitation (AVVR) remains a significant complication post-Fontan. This study evaluates the accuracy of 4D flow AVVR quantification in post-Fontan patients by comparing 4D flow to conventional echocardiographic (AVVREcho) and CMR assessments. Patients in the multi-institutional FORCE registry with high-quality 4D flow CMR were included. Regurgitant fractions (RFs) were calculated using two 4D-flow based methods: AVVRAVV-Ao (4D), calculated from atrioventricular valve and aortic flows, and AVVRJet, which directly measures AVVR jet volume. 4D flow RFs and severity classifications were compared with AVVREcho and CMR-reported AVVR severity (AVVRReport-Cat), and examiner-reported RFs (AVVRReport-RF). Statistical tests included Pearson correlation, Cohen's kappa, and Bland-Altman analysis. The study included 218 post-Fontan patients (median age: 16.2 years, IQR: 12.8-22.5) and 36.2% were female. Both 4D flow methods displayed excellent interobserver reproducibility (interclass correlation > 0.95) and RFs approximately 7% lower than AVVRReport-RF. AVVRAVV-Ao (4D) showed stronger agreement with AVVRReport-RF (κ = 0.50 [95% CI: 0.25-0.75]; r = 0.49, p < 0.01). AVVRJet​ demonstrated better concordance with AVVRReport-Cat (κ = 0.31 [95% CI: 0.17-0.45]). Both AVVRAVV-Ao (4D) (OR = 1.53, p = 0.004; AUC = 0.71) and AVVRJet (OR = 1.74, p = 0.002; AUC = 0.65) were associated significantly with the composite outcome of death and heart transplantation listing. This is the first study analyzing the accuracy of 4D flow AVVR quantification in post-Fontan patients, demonstrating reproducibility, prognostic value, and good concordance with conventional methods. These findings suggest that 4D flow AVVR quantification may serve as a complementary method for assessing AVVR in post-Fontan patients.