4D Flow MRI Characterization of Left Atrial Vortical Flow in Atrial Fibrillation Following Catheter Ablation.

Atrial fibrillation (AF) is associated with abnormal left atrial (LA) blood flow patterns that contribute to thromboembolic risk. While blood flow stasis in AF has been extensively studied, the effects of AF and pulmonary vein isolation (PVI) on LA vortical flow remain incompletely understood. This study used four-dimensional flow magnetic resonance imaging to quantify LA vorticity and vortex volume in 107 patients with AF before PVI, 56 patients after PVI, and 19 non-AF controls. Vortex structures were identified using the Lambda2 method, and group differences were assessed after adjustment for age and sex. Pre-ablation patients demonstrated significantly lower LA vorticity than both post-ablation patients and controls, whereas post-ablation patients did not differ from controls. In contrast, mean and maximum LA vortex volumes remained elevated in both AF groups relative to controls, with no significant differences between pre- and post-ablation patients. These findings indicate that PVI is associated with improvements in LA vorticity but not vortex volume. The persistence of enlarged LA vortices despite normalization of vorticity suggests that these metrics capture distinct aspects of atrial remodeling and may provide complementary insight into AF-related pathophysiology.