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

Study Questions:

What is the impact of rapid access to medical care and reperfusion in patients with in-hospital compared with out-of-hospital stent thrombosis (ST) in patients with ST-segment elevation myocardial infarction (STEMI)?


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. The authors investigated the 1-year clinical outcomes after ST in 54 patients with in-hospital ST compared with 102 patients with out-of-hospital ST.


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). 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, 1.98-10.77; p < 0.01). Additional correlates of increased mortality after an ST event included diabetes and randomization to UFH + GPI (vs. bivalirudin).


The authors concluded that mortality and major bleeding were significantly higher after in-hospital ST compared with out-of-hospital ST.


This study reports that in patients with STEMI undergoing primary PCI with stent implantation, more than one third of all ST events during the 3-year follow-up period occurred during the hospital phase, shortly after the index procedure. One-year mortality after ST was significantly higher in patients with in-hospital compared with out-of hospital ST, despite more rapid access to care and similar rates of target lesion revascularization. Furthermore, the occurrence of in-hospital compared with out-of-hospital definite or probable ST was an independent predictor of greater mortality after multivariate adjustment, both with and without the use of a propensity score. Since the original stent implantation was performed in this analysis in patients presenting with STEMI, additional studies are indicated to determine whether an early in-hospital ST event may also be less catastrophic in patients undergoing elective stent implantation.

Clinical Topics: Anticoagulation Management, Invasive Cardiovascular Angiography and Intervention

Keywords: Myocardial Infarction, Follow-Up Studies, Gadolinium, Heparin, Angioplasty, Balloon, Coronary, Hirudins, Percutaneous Coronary Intervention, Stents, Thrombosis, Recombinant Proteins, Cardiovascular Diseases, Diabetes Mellitus, Hemorrhage, Platelet Glycoprotein GPIIb-IIIa Complex

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