['The clinical significance of left atrial pressure (LAP) has not yet been clearly elucidated in patients with atrial fibrillation (AF).', 'To explore the effects of elevated LAP on pathophysiology and clinical outcome after radiofrequency catheter ablation in patients with AF.', 'We measured LAP during both sinus rhythm (SR) and AF in 454 patients 348 (76.7%) men; mean age 58 ± 11 years; 326(71.8%) paroxysmal AF) who underwent radiofrequency catheter ablation and compared LAP at v wave (LAPpeak) and LAP at y descent (LAPnadir) by using imaging (echocardiography and computed tomography), electrophysiologic mapping (NavX), and clinical data. In 280 (61.7%) patients, pulmonary vein (PV) diastolic flow velocity was measured during SR by transesophageal echocardiography.', 'Patients with LAPpeak(SR) ≥19 mm Hg had greater left atrial (LA) dimension (P < .001), LA volume index (P = .003), and E/Em (mitral annular septal area [peak diastolic velocity]; P = .001) but reduced LA voltage (P < .001) and mitral annular septal area (peak systolic velocity; P = .006) compared with patients with LAPpeak(SR) <19 mm Hg. High LAPpeak(SR) was independently associated with anterior LA volume (linear regression coefficient [B] = 0.381; 95% confidence interval [CI] 0.169-0.593; P < .001) and low LA voltage (B = -0.022; 95% CI -0.030 to -0.013; P < .001). PV diastolic flow velocity (B = 0.161; 95% CI 0.083-0.239; P < .001) and E/Em (B = 0.430; 95% CI 0.096-0.763; P = .012) were independent, noninvasive parameters associated with high LApeak(SR). During 13.1 ± 6.0 months of follow-up, high LAPpeak(SR) was an independent predictor for clinical recurrence of AF (hazard ratio 1.887; 95% CI 1.063-3.350; P = .028).'] Are high left atrial pressures associated with advanced electroanatomical remodeling of left atrium and independent predictors for clinical recurrence of atrial fibrillation after catheter ablation?