Stent thrombosis after primary angioplasty for STEMI in relation to non-adherence to dual antiplatelet therapy over time: results of the HORIZONS-AMI trial.

AIMS: Rates of stent thrombosis (ST) after ST-elevation myocardial infarction (STEMI) may vary over time and the relationship of this complication with non-adherence to dual antiplatelet therapy (DAPT) during long-term follow-up remains unclear.

METHODS AND RESULTS: We analysed 2,997 patients who were treated with at least one stent and in whom a non-target vessel ST did not occur during follow-up from the large-scale Harmonizing Outcomes with Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) trial of patients with STEMI undergoing primary percutaneous coronary intervention (PCI). Aspirin was prescribed indefinitely, and a thienopyridine for at least six months. DAPT usage was evaluated according to the development of ST in four time periods (<1 month, 1-6 months, 6-12 months and >1 year from index stent implantation). DAPT non-usage was lowest within the first month, but was strongly associated with ST. During the 1-6 month period the relationship remained strong, but was absent in the 6-12 month period. Beyond one year, ST was associated with non-usage of aspirin but was paradoxically more common in patients taking a thienopyridine.

CONCLUSIONS: The relationship between stent thrombosis and non-adherence to DAPT varies over time. It is strong within the first month, remains important until six-month follow-up but fades afterwards. Very late ST is associated with both DAPT and aspirin alone but not with thienopyridine non-adherence.