Atrial platelet reactivity in patients with atrial fibrillation

Background Atrial fibrillation (AF) is associated with an increased risk of thrombus formation in the left but not the right atrium. The mechanisms underlying this differential effect on the atria are unknown. Objective The purpose of this study was to examine whether atrial-specific differences in platelet activation are present in patients with AF. Methods Nineteen patients (13 men and 6 women; age 60 ± 2 years) with AF undergoing ablation in sinus rhythm were studied. Blood samples from the left atrium, right atrium, and femoral vein were obtained at the start of the procedure and analyzed by whole-blood flow cytometry for expression of platelet P-selectin (CD62P), vitronectin receptor (CD51/61), and active glycoprotein IIb/IIIa receptor (PAC-1). Platelet aggregation was evaluated using adenosine diphosphate (ADP)-induced whole-blood impedance aggregometry. Seven patients with left-sided accessory pathway also were studies as a reference group for the effect of transseptal puncture on platelet reactivity. Results Platelet P-selectin levels were significantly elevated in the left atrium compared to the right atrium (10.2% ± 2.5% vs 8.6% ± 2.3%, P