December 2016

Patients with atrial fibrillation who are being treated with oral thrombin inhibitors (OTIs) have a slightly increased risk for cardiac infarction compared to patients receiving vitamin K antagonists. Up to now the reason for this was unclear. DZHK researchers led by Tobias Petzold and Steffen Massberg from the Munich partner site investigated this effect in the laboratory and were able to confirm the observations experimentally. They found that patient blood containing OTIs tends towards increased platelet aggregation under flow conditions, but not under static conditions. The effect was especially pronounced on surfaces coated with components of human atherosclerotic plaques. In blood of patients treated with vitamin K antagonists they did not observe the same effects. In in vivo models of arterial thromboses, administration of OTIs led to increased thrombus formation. The investigators suspect that this prothrombotic effect is brought about by the OTI influencing the binding behaviour of a receptor which mediates thrombin binding to the thrombocytes. By blocking this interaction with the help of antibodies, those prothrombotic effects can be prevented. In terms of clinical practice, these findings could mean that atrial fibrillation patients with coronary heart disease or a generally increased risk for cardiac infarction should not be treated with OTIs.