['The underlying mechanisms of increased risk of thrombo-embolism in atrial fibrillation (AF) are not completely understood; however, substantial evidence supports that AF is associated with a prothrombotic state. Accordingly, we hypothesized that strict rate control could attenuate platelet activity and thrombotic state in patients with non-valvular AF.', 'Seventy-five patients with non-valvular AF were divided into 2 groups based on heart rate: (1) normal ventricular rate (n = 34, 18 female) and (2) high ventricular rate (n = 39). Thirty-three sex- and age-matched subjects in sinus rhythm were included as control. Thirty patients with high ventricular rate (16 female) were successfully followed. Markers of platelet function were measured at baseline and repeated 1-month after adequate rate control in high ventricular rate group.', 'Serum fibrinogen levels were significantly higher in AF patients with high ventricular rate than that in controls. Mean platelet volume, soluble CD40L and β-Thromboglobulin were significantly higher in AF patients with high ventricular rate than those in both AF patients with normal ventricular rate and controls. Soluble CD40L and β-Thromboglobulin were significantly higher in AF patients with normal ventricular rate than those in controls. One-month after adequate rate control, serum fibrinogen, soluble CD40L and β-Thromboglobulin levels significantly decreased (from 2.26 ± 1.02, 85.01 ± 37.05, 3.10 ± 0.90 to 1.55 ± 1.08, 66.34 ± 33.72, 2.71 ± 0.53; p < 0.001, p = 0.002, p = 0.03, respectively) in high ventricular rate group.'] Does strict heart rate control attenuate prothrombotic state and platelet activity in patients with non-valvular permanent atrial fibrillation?