According to the findings of an analysis of the HORIZONS-AMI study, use of a combination of aspirin, thienopyridine and vitamin K antagonist (VKA) following STEMI treated with primary percutaneous coronary intervention (PCI) increases bleeding complications and may result in temporary discontinuation of VKA.

The authors note that oral anticoagulants are recommended for certain patients post-STEMI (e.g. for those with a large akinetic region in the left ventricle; mural thrombus; persistant or paroxysmal AF) and that triple therapy (aspirin, thienopyridine and VKA) is required for patients treated with primary PCI using stents, who are at a high risk of systemic emboli.  The risks and benefits of such triple therapy in STEMI patients undergoing primary PCI have not however been fully characterised.  The purpose of their study was to assess the outcomes of patients receiving triple therapy in the large HORIZONS-AMI trial, which compared bivalirudin to unfractionated heparin plus a glycoprotein IIb/IIIa inhibitor in 3,602 adults with acute STEMI.     

A total of 126 patients (3.8%) of the 3,320 who were triaged to primary PCI were prescribed triple therapy and the remainder were prescribed dual antiplatelet therapy (i.e. no VKA).   The most frequent indications for VKA treatment included a severely reduced left ventricular ejection fraction with a large akinetic area (23.8%), atrial fibrillation (23.8%), and mural thrombus (23.0%).  Those receiving triple therapy were more likely to be older, female, and have a history of rhythm disturbances, a lower left ventricular ejection fraction, left anterior descending artery territory infarcts, and Final Thrombolysis In Myocardial Infarction (TIMI) flow grade <3.

Patients treated with triple therapy had similar short- and long-term ischaemic outcomes to those treated with dual therapy, but they had increased rates of major bleeding during the index hospitalisation (17.1% vs. 6.5%, p <0.0001).  A total of 15 of the 105 patients (14.3%) who started VKA treatment during their admission had it stopped prematurely because of this.  Rates of all-cause and cardiac mortality, reinfarction and target vessel revascularisation over one year did not differ between the triple and dual therapy groups; however there were greater rates of stroke at one year of follow-up in the triple group (one additional case of ischaemic stroke and another of haemorrhage stroke).

The authors comment that the risk of adding oral anticoagulation to patients admitted for STEMI should be carefully considered before choosing drug-eluting or bare metal stents.