Do patients with persistent atrial fibrillation have more dispersion of left atrial refractoriness and conduction before development of overt fibrosis?

Abstract Background In patients with persistent atrial fibrillation (PS AF) undergoing pulmonary vein isolation (PVI), left atrial fibrosis, as assessed by voltage mapping prior to ablation, is more common than in patients with paroxysmal (PX) AF. Little is known, however, if subtle changes in left atrial conduction properties, such as conduction time and effective refractory periods (ERP) precede true structural abnormalities and allow to differentiate between PS AF and PX AF. Study aim To test the hypothesis that patients with PS AF demonstrate a larger local left atrial dispersion of conduction and refractoriness, as compared to patients with PX AF. Patients and methods: A total of 49 patients undergoing PVI for symptomatic AF were studied off antiarrhythmic drugs (PX AF, N=35, PS AF [history of cardioversion], N=14). Prior to PVI, a voltage map was performed, using the NAVX™ system and the HD Grid™ mapping catheter. Patients with significant structural heart disease and detectable left atrial fibrosis (voltage < 0.5 mV) were excluded. Local ERP during programmed stimulation was assessed, using the HD Grid™ catheter: On the back of the left atrium, close to the ostium of the left upper pulmonary vein (LUPV), the left lower (LL) PV, the right upper (RU) PV, the right lower (RL) PV, the high interatrial septum (area of Bachmann´s bundle) and the low interatrial septum (between the coronary sinus ostium and the RLPV). The interatrial conduction time was assessed between the HD Grid™ and a catheter in the right atrium. Comparison between groups was performed using the Mann-Whitney U-test. A p value < 0.05 was considered significant Results In this cohort of 49 patients without evidence of overt left atrial fibrosis undergoing ablation for symptomatic AF, no significant differences could be detected between patients with PX AF and PS AF with respect to local dispersion of refractoriness or interatrial conduction. Conclusion In patients with symptomatic AF and no evidence of left atrial fibrosis, local left atrial parameters of refractoriness and conduction did not show any significant differences between the cohort of PS AF and PX AF patients.