Clinical outcomes following stent thrombosis occurring in-hospital versus out-of-hospital: results from the HORIZONS-AMI (Harmonizing Outcomes with Revascularization and Stents in Acute Myocardial Infarction) trial.

OBJECTIVES: The study sought to determine whether rapid access to medical care and reperfusion results in a better prognosis in patients with in-hospital compared with out-of-hospital stent thrombosis (ST) in patients with ST-segment elevation myocardial infarction (STEMI) in the HORIZONS-AMI (Harmonizing Outcomes with Revascularization and Stents in Acute Myocardial Infarction) trial.

BACKGROUND: Whether the prognosis of in-hospital and out-of-hospital ST are similar is uncertain, with conflicting data reported from prior studies.

METHODS: A total of 3,602 STEMI patients undergoing primary percutaneous coronary intervention (PCI) were randomized to bivalirudin (n = 1,800) versus unfractionated heparin (UFH) plus a glycoprotein IIb/IIIa inhibitor (GPI) (UFH+GPI; n = 1,802). Stents were implanted in 3,202 patients, 156 (4.9%) of whom developed Academic Research Consortium definite/probable ST during 3-year follow-up. We investigated the 1-year clinical outcomes after ST in 54 patients with in-hospital ST compared with 102 patients with out-of-hospital ST.

RESULTS: One year after the ST event, patients with in-hospital compared with out-of-hospital ST had significantly greater mortality (27.8% vs. 10.8%, p < 0.01); most deaths in both groups occurred within 1 week of the ST event. Patients with in-hospital ST also had higher rates of major bleeding (21.2% vs. 6.0%, p < 0.01), but a lower rate of myocardial infarction (56.6% vs. 77.5%, p < 0.01). Subgroup analysis within both in-hospital and out-of-hospital ST groups indicated that subacute ST had the highest mortality. By multivariable analysis, 1-year mortality was significantly increased in patients with in-hospital compared with out-of-hospital ST (adjusted hazard ratio: 4.62, 95% confidence interval: 1.98 to 10.77, p < 0.01). Additional correlates of increased mortality after an ST event included diabetes and randomization to UFH+GPI (vs. bivalirudin).

CONCLUSIONS: Following primary PCI for STEMI, more than one-third of all ST events during 3-year follow-up occurred during the index hospital phase. Mortality and major bleeding were significantly higher after in-hospital ST compared with out-of-hospital ST. (Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction; NCT00433966).