4D Flow Component Reveals Left Ventricular Function In Atrial Fibrillation

Purpose: Applicating cardiovascular magnetic resonance (CMR) 4D flow to evaluate left ventricular systolic and diastolic function in atrial fibrillation (AF). Methods: In this study, from May 2021 to October 2021, 26 AF patients and 15 healthy participants were recruited and underwent multiparametric CMR and echocardiogram scans before discharge. The CMR protocol incorporated an assessment of 4D flow, cardiac function. Notably, the AF patients maintained irregular heart rhythm during the CMR scan. The 4D flow components were compared with echocardiogram results. Results: AF patients had a lower proportion of direct flow (33.5% (8.43; 47.5) in AF vs. 69.1% (63.4; 74.4) in healthy), higher delayed ejection (24.1±12% in AF vs. 14.7±6.8% in healthy), retained inflow (32.5% (24.6; 36.9) in AF vs. 14.5% (12.5; 18.2) in healthy) and residual volume (4.73% (1.47; 15.0) in AF vs. 0.62% (0.46; 1.62) in healthy). A high correlation was observed between flow EF and CMR EF (R=0.78, P<0.001) in AF patients. The mean bias among the methods was higher for flow EF than CMR EF (24.86%). Multivariable linear regression showed that the correlation between retained inflow and E/e’ (β=0.152, P=0.048) remained significant when adjusted for confounders. Direct flow (β= -0.170, P=0.038) and retained inflow (β=0.350, P=0.024) significantly correlated with the Minnesota Living with Heart Failure Questionnaire score. Conclusion: CMR 4D flow component revealed a significantly different flow pattern in AF patients compared with healthy participants and provided de novo flow biomarker indicating LV systolic function (direct flow and flow EF) and diastolic function (retained inflow).