Enhanced expression of platelet CD40-ligand by in vitro lipopolysaccharide-challenge in patients with ventricular fibrillation complicating acute myocardial infarction

BACKGROUND: Acute myocardial infarction can be complicated by ventricular arrhythmias due to electrophysiological changes in the ischemic myocardium, but the exact predisposing factors causing ventricular fibrillation during myocardial infarction still remain unclear. A role of inflammatory stimulation on platelets as a potential risk factor for ventricular fibrillation during acute myocardial infarction has not been described yet. METHODS AND RESULTS: Whole blood samples of 21 patients with a history of acute myocardial infarction (AMI) and ventricular fibrillation (VF) were incubated with lipopolysaccharide (LPS). As a control group, we studied 19 patients without VF during AMI. CD40-ligand and CD62P expression on platelets and tissue factor binding on monocytes were measured by flow cytometry. Platelet-monocyte aggregates were measured by CD41 expression on platelets adherent to monocytes. Soluble CD40-ligand plasma levels were measured with an ELISA. Without LPS, no significant difference between the patient groups concerning CD40L expression on platelets was observed, but plasma levels of soluble CD40L were significantly higher in patients with a history of AMI with VF. After LPS stimulation, patients with a history of VF showed a significantly increased expression of CD40L in comparison to the patients without ventricular fibrillation, based on a significantly higher increase of CD40L expression. CD62P expression on platelets was significantly increased in patients with a history of VF. CONCLUSIONS: Patients with a history of VF complicating AMI show an enhanced expression of CD40L on platelets after in vitro lipopolysaccharide-challenge with an enhanced platelet activation.