1. Introduction

Antithrombotic therapy such as antiplatelet drugs and oral anticoagulation (OAC) are used extensively to treat and prevent thromboembolic events by inhibiting platelet aggregation and coagulation. OAC (vitamin K-antagonist (VKA, coumarines) and direct oral anticoagulation (DOAC) therapy) is recommended for the prevention of stroke in patients with atrial fibrillation (AF) and systemic embolism, while antiplatelet therapy (platelet aggregation inhibitors (PAI) such as acetylsalicylic acid and P2Y12 inhibitors) is recommended for the prevention of (recurrent) myocardial infarction and stent thrombosis.
The patient population on antithrombotic therapy is growing and the antithrombotic landscape is complex. In clinical practice, a subgroup of patients have an indication for both OAC and antiplatelet therapy.1-4 However, combining OAC with other antithrombotic agents is associated with a high risk of bleeding complications.5,6 In addition, the complexity of guidelines and schedules for combined antithrombotic therapy could cause unnecessarily prolonged continuation of this combined therapy. Due to this complexity, medication errors may occur. 7-11 In fact, antithrombotics are the most common cause of potentially avoidable adverse events that result in a prolonged hospitalisation compared to other medications. 12-14 For these reasons, combined antithrombotic therapy should be monitored closely to prevent unintentional longer use than indicated, avoidable bleeding complications and unnecessary (re)hospitalizations. Therefore, our hospital has implemented a multidisciplinary antithrombotic stewardship (ASP) to proactively monitor the in-patients safety and efficacy of daily antithrombotic therapy use.
The main objective of this study is to determine the efficacy of the ASP by assessing the number of patients on combined antithrombotic therapy for whom one or more interventions are needed by ASP to optimize the antithrombotic therapy. Secondarily, reasons for intervention are explored. Furthermore, we aim to describe the safety outcomes such as bleeding and thromboembolic complications in patients on combined antithrombotic therapy.