Platelet expression of CD40/CD40 ligand and its relation to inflammatory markers and adhesion molecules in patients with atrial fibrillation.

Recent studies suggest the importance of prothrombotic and proinflammatory cascades in vascular thrombus formation. However, the impact of platelet CD40 and CD40 ligand (CD40L) expression and its relation to inflammatory markers in atrial clot formation have not yet been determined. Therefore, we studied a total of 40 patients. A total of 20 patients with persistent atrial fibrillation (AF) and 20 matched patients with sinus rhythm (SR) were included to quantify platelet surface expression of CD40/CD40L, serum levels of intercellular adhesion molecule-1 (ICAM), vascular adhesion molecule-1 (VCAM), high-sensitivity C-reactive protein (hsCRP), and monocyte chemoattractant protein-1 (MCP-1). Using fluorescence-activated cell sorting analysis, baseline CD40 expression (antibody binding capacity [ABC]) was increased during AF (AF: 7776 +/- 8.46 ABC vs. SR: 7753 +/- 7.32 ABC; P < 0.05), whereas CD40L expression was not different. In contrast to the effect of adenosine diphosphate, ex vivo stimulation with thrombin receptor activating peptide (TRAP) increased CD40 and CD40L expression in both groups. MCP-1, hsCRP, ICAM, and VCAM levels were significantly increased during AF, reaching highest levels in patients with atrial thrombi. Importantly, VCAM and MCP-1 were independent predictors for atrial thrombi (P < 0.05) using multivariate analysis. In contrast to declining levels of hsCRP, levels of ICAM, VCAM, MCP-1, and platelet CD40 expression remained elevated 5 weeks after successful electrical direct current cardioversion (CV). In conclusion, prothrombogenic markers are substantially elevated in patients with AF, reaching highest levels in patients with AF and atrial thrombi. Interestingly, amounts of adhesion molecules and platelet CD40 levels remain elevated even 5 weeks after successful CV, which may imply a persistently increased risk for atrial thrombus formation. In addition to hsCRP, MCP-1 and VCAM may serve as new biomarkers, which may help to identify patients with an increased risk for thromboembolic events.