In atrial fibrillation (AF), few studies have focused on the influence of the mode of restoration of sinus rhythm (SR) on cardiac cavities remodelling, especially after spontaneous restoration.

To determine the phenotype of patients with AF and spontaneous restoration of SR.

We prospectively studied 184 patients hospitalized for AF with restoration of SR at 6-month follow-up. Patients were divided into two groups at 6 months according to the type of restoration of SR: spontaneous (Spontaneous SR group; n=57) or active (pharmacological and/or electrical and/or ablation; Active SR group; n=127). Each patient underwent comprehensive clinical, biological and two-dimensional (2D) transthoracic echocardiography studies at 6-month follow-up. 2D parameters, including strain parameters, were analysed offline using Ultrasound Workspace software (Philips).

At 6-month follow-up, 111 patients (60.3%) were male, the median (interquartile range) age was 66.7 (55.6–73.4) years and 48 (26.1%) had a CHA₂DS₂-VA score≥2. On univariate analysis, the Spontaneous SR group had lower body surface area, less heart failure (HF) associated with AF, lower glycated haemoglobin, lower B-type natriuretic peptide and higher high-density lipoprotein cholesterol than the Active SR group at 6-month follow-up. Concerning the echocardiographic evaluation, the Spontaneous SR group had lower biplane left atrial (LA) volume, higher LA reservoir, conduit and contractile strains, and higher right ventricular free wall strain than the Active SR group at 6-month follow-up. Lower body surface area (odds ratio [OR] 0.79 per 0.1 m² increase, 95% confidence interval [CI] 0.65–0.95; P=0.012), absence of HF associated with AF (OR 0.17 for HF, 95% CI 0.05–0.54; P=0.003) and higher LA reservoir strain (OR 1.21 per 5% increase, 95% CI 1.02–1.45; P=0.028) remained significantly associated with spontaneous restoration of SR after multivariable adjustment.

Spontaneous restoration of SR corresponds to a distinct phenotypic group of patients with AF with less atrial remodelling. LA reservoir strain appears to be an interesting biomarker for differentiating the degree of atrial remodelling. Further investigations are warranted to determine the impact of such abnormalities on the risk of AF recurrence and cardiovascular events.