Does Bipolar Pacemaker Current Activate Blood Platelets?

Objective: The aim of this study was to investigate whether bipolar pacemaker current lead can activate blood platelets. The null hypothesis was that 1 minute of electrical stimulation of platelets would not influence their subsequent reactivity to adenosine diphosphate (ADP).Background: Both platelets and muscle cells contain actin and myosin filaments, and both cells are activated following calcium influx. Muscle cells open their calcium channels and contract when exposed to an electric current. Current through a bipolar pacemaker lead will expose a small volume of blood, including platelets, to the depolarizing current. Platelet activation may ensue, resulting in aggregation, release reaction, and contraction. In contrast, a unipolar pacemaker system will not depolarize blood, but transmit current directly into the myocardium, and the current afterward passes through other tissues before returning to the pacemaker can.Methods: Platelet‐rich plasma was prepared from two healthy subjects. Platelet reactivity to the agonist ADP was tested in paired samples in an aggregometer in a case/control setup.Results: Eighteen of 46 tested pairs of platelet‐rich plasma showed increased reactivity in the paced sample; 26 were unchanged while two showed decreased reactivity in the paced sample. Using a two‐sided sign test, the null hypothesis was rejected (P = 0.0004).Conclusions: The study demonstrates increased reactivity to ADP in platelets exposed in vitro to stimulation by pacemaker current. The clinical relevance of these findings remains to be investigated.