Measuring Atrioventricular Valve Regurgitation in Fontan Patients Using Cardiac MRI and the Association with Clinical Outcomes: A FORCE Study

Background Atrioventricular valve regurgitation (AVVR) predicts long-term post-Fontan adverse outcomes. Literature on the measurement and prognostic value of quantitative AVVR assessment using cardiac magnetic resonance imaging (CMR) is limited. This study compared echocardiographic AVVR measurements with measurements by CMR, and investigated their association with clinical outcomes using the multi-center F ontan O utcome R egistry using C MR E xamination (FORCE). Methods Patients with an examiner-reported AVVR severity category from CMR (AVVR Report-Cat ) and an AVVR from matched echocardiography (AVVR Echo ) were included. Three quantitative CMR AVVR regurgitant fraction were used: (1) stroke volume and antegrade aortic flow (AVVR Standard ), (2) atrioventricular valve flow and antegrade aortic flow (AVVR AVV-AO ), and (3) examiner-reported regurgitation fraction (AVVR Report-RF ). Moderate AVVR was defined as regurgitant fraction of 20-40% and severe >40%. The concordance across methods was calculated using Kappa statistics, and associations with outcomes of mortality or listing for/receiving heart transplantation were analyzed using Cox proportional hazard models. C-statistic was used to compare model performance. Results 2,309 Fontan patients were included, with a median age at CMR of 15.7 years and 42.1% female. Categorical AVVR severity reported by CMR was significantly associated with adverse outcomes (adjusted HR 2.10, 95% CI [1.38, 3.19] for moderate and 4.61 [2.80, 7.58] for severe AVVR), comparable to AVVR reported by echocardiography. AVVR AVV-AO showed stronger concordance with AVVR Report-Cat (Kappa=0.58) and higher hazards of the adverse outcome than AVVR Standard . The subset of patients with examiner-reported regurgitation fraction (AVVR Report-RF ) showed the highest hazard associated with AVVR and the highest C-statistic among all methods including echocardiography. Conclusions This is the first study evaluating different CMR measurements of AVVR in a large cohort of Fontan patients. Compared with AVVR Standard , AVVR AVV-AO had higher concordance with the reported categorical AVVR using CMR. Moderate and severe AVVR determined by both CMR and echocardiography were associated with comparably increased hazards of adverse clinical outcomes.