Abstract Body (Do not enter title and authors here): Introduction In atrial fibrillation (AF), few studies have focused on the influence of the mode of cardioversion (CV), spontaneous (SpCV) versus non spontaneous (noSpCV) on cardiac cavities remodeling.

Purpose We hypothesized that patients with SpCV might have a distinct morphological pattern in AF according to the mode of sinus rhythm conversion.

Methods We prospectively studied 347 patients hospitalized for AF using two-dimensional (2D) transthoracic (TTE) and evaluated 4 cardiac chambers remodeling. 2D parameters, including strain parameters, were off-line analysed using Ultrasound Workspace software (4D Cardio-View, Philips). Patients were divided into two groups according to cardiac rhythm within 24 hours after admission: SpCV group, 77 patients and noSpCV group, 270 patients. All patients in SpCV group were in sinus ryhtm during TTE, whereas the patients in noSpCV group were in AF.

Results Median age was 68.0 (58.7-74.9) years and 210 (60.5%) patients were male.
SpCV group had in comparison with noSpCV group less diabetes frequency (8(10.4%)) versus 59 (21.9%), p=0.032), tobacco use 25 (32.5%) versus 143 (53%), p=0.002) , alcohol use (15 (19.5%) versus 88 (32.6%) p= 0.033), history of AF (14 (18.2%) versus 92 (34.1%); p = 0.008), history of HF (3 (3.9%) versus 46 (17%); p= 0.003). Patients with SpCV group were at lower thrombo-embolic risk, CHADS VA>2 (16 (20.8%) versus 96 (35.6%); p=0.018). SpCV group had higher LVEF, lower LV filling pressure, lower indexed left and right atrial end-systolic (ES) volume, lower E velocity (p<0.001), and higher left ventricular ejection fraction, LVEF (Table 1), as compared with noSpCV group (Table 1). Interestingly, SpCV group had higher strain of the four chambers in comparison with non SpCV group (Figure 1).

Conclusions Four chambers remodeling at baseline seems to be less marked in SpCV group. Further investigations are warranted to determine the impact of such abnormalities on the risk of cardiovascular events in AF patients, including the risk of AF recurrences at follow-up.