Relation of Echocardiographic Markers of Left Atrial Fibrosis to Atrial Fibrillation Burden

In patients with atrial fibrillation (AF), left atrial (LA) fibrosis is a major determinant of the progression to, and burden of AF. LA reservoir strain and total atrial conduction time (PA-TDI) reflect LA fibrotic content. We aimed to investigate the relation between LA reservoir strain and PA-TDI in AF patients and control subjects. Six-hundred two patients (mean age 56 years, 53% men) with first episode of AF and 342 controls (mean age 64 years, 71% men) without structural heart disease underwent echocardiography. LA volumes, PA-TDI, LA reservoir strain, and left ventricular global longitudinal strain (GLS) were compared. Compared with controls, patients with paroxysmal AF and patients with persistent AF had longer PA-TDI (128 ± 25 millisecond, 140 ± 31 millisecond, and 154 ± 33 millisecond, respectively; p <0.001) and a progressive decline in LA reservoir strain (36.9 ± 11.6%, 29.8 ± 13.4%, 24.2 ± 12.3%, respectively; p <0.001). LA reservoir strain was negatively correlated with PA-TDI (r = -0.43, p <0.001). On multivariate analyses, LA reservoir strain, diabetes mellitus, and burden of AF were independent correlates of PA-TDI (R2 = 0.23, p <0.001); whereas only PA-TDI was an independent correlate of LA reservoir strain (R2 = 0.43, p <0.001); controlling for age, hypertension, coronary artery disease, body mass index, severity of mitral regurgitation, left ventricular global longitudinal strain, and LA volume. In conclusion, PA-TDI and LA reservoir strain are negatively correlated in all subjects, irrespective of the presence or burden of AF. Patients with persistent AF have longer PA-TDI and impaired LA reservoir strain compared with paroxysmal AF and controls, suggesting increasing burden of fibrosis and LA structural remodeling in the progression of AF.