Abstract 13614: Why the Pulmonary Veins: Linking Atrial 4D Flow MRI Derived Biomechanics and Pulmonary Vein Electrical Remodeling

Introduction: Pulmonary veins (PV) often trigger atrial fibrillation (AF). However, the underlying mechanism is not completely understood and predicting who benefits from PV isolation (PVI) is imprecise. We propose that arrhythmogenic PV remodeling may be related to myocardial mechanical function. Flow-encoded cardiac magnetic resonance imaging (4D Flow MRI) based computational modeling enables assessment of left atrial (LA) hemodynamics and biomechanics. In this pilot study, 4D Flow MRI derived parameters were compared to invasive electroanatomic mapping (EAM) and hemodynamics to explore potential non-invasive evaluation of PV remodeling and arrhythmogenicity. Methods: Patients (5 female, 4 male, age 64±6.7 years) with paroxysmal or early persistent AF scheduled for PVI were enrolled. All patients underwent 4D Flow MRI prior to ablation (in sinus rhythm) and intraprocedural EAM (Carto) with atrial pacing under baseline conditions and after increasing LA pressure with a fluid bolus. Non-invasive measures included peak and average velocity (m/s) and net flow (ml/cycle) in each vein (n=36) and averaged for each patient. Apparent conduction velocities in the proximal, mid and distal portions of each vein were calculated under baseline and stretch conditions from EAM. Change in LA pressure per volume bolus, a measure of atrial stiffness, was compared to non-invasive parameters. Results: In patients with LA stiffness greater than median, peak velocities (0.77±0.12 vs. 0.62±0.24 m/s, p=0.26) and net flows were higher (17±2.0 vs. 14.0±2.4 ml/cycle, p=0.06). Patients with paroxysms of spontaneous arrhythmias during mapping had higher LA stiffness (11.5±5.7 vs. 7.6±5.3 mmHg/L, p=0.30). There was a significant correlation between non-invasive average velocity and apparent conduction velocity in the proximal portion of the vein (R=-0.36, p=0.03) and the suggestion of a correlation between increasing peak flow velocity and decreased apparent conduction velocity under stretch conditions compared to baseline (R=-0.24, p=0.16). Conclusions: Our findings may indicate a link between atrial hemodynamics, electrical remodeling and PV arrhythmogenicity. Additional studies are warranted to confirm and better define these findings.