Left atrial vortex size and velocity distributions by 4D flow MRI in patients with paroxysmal atrial fibrillation: Associations with age and CHA2DS2-VASc risk score

Background Characterization of left atrial (LA) hemodynamics in paroxysmal atrial fibrillation (PAF) may provide valuable insights for thromboembolic risk. Purpose To evaluate LA vortex formation and velocity distributions by 4D flow MRI and identify associations with age, LA/LV (left ventricle) function, and established risk scores. Study Type Prospective clinical. Population Patients with PAF (n = 45, 46 +/- 14 years) and healthy controls (n = 15, 54 +/- 9 years) were enrolled. MRI Sequences 3T standardized cardiac MRI protocol inclusive of 4D flow MRI. Assessment Flow analysis planes were prescribed at each pulmonary vein. Velocity distribution analysis and vortex size quantification by the Lambda2 (lambda(2)) method were performed in the LA. Statistics Pearson or Spearman's correlation coefficients, r, were calculated to identify relationships between 4D flow-derived LA parameters and age, LA/LV function, and CHA(2)DS(2)-VASc stroke risk score. Univariate and multivariate determinants of stroke risk were assessed using linear regressions. To compare parameters within multiple groups, one-way analysis of variance or Kruskal-Wallis was used. Results LA vortice sizes were observed in all subjects using lambda(2) showing inverse correlations with peak pulmonary vein inflow velocities (P < 0.05), and positive correlations with LA volume (P < 0.05). Vortex size was elevated in PAF at all phases of the cardiac cycle, being most prominent at end early diastole (3.98 +/- 1.84 cm(3) vs. 6.93 +/- 3.11 cm(3), P = 0.001). Velocity distribution analysis showed a greater incidence of flow stasis among patients with PAF (P < 0.05). In univariate regression, vortex size was associated with the CHA(2)DS(2)-VASc risk score at peak systole (0.457 +/- 0.038, P <= 0.001). However, in multivariate regression age was the dominant determinant of stroke risk (0.348 +/- 0.012, P = 0.006). Data Conclusion This study demonstrated that LA vortex size is increased among low-risk patients with PAF and is associated with the CHA(2)DS(2)-VASc risk score. Age remained the dominant determinant of stroke risk. Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019.