Frequency and Predictors of Stent Thrombosis After Percutaneous Coronary Intervention in Acute Myocardial Infarction

Study Questions:

What are the frequency and predictors of stent thrombosis occurring within the first 2 years after stent implantation in patients with ST-segment elevation myocardial infarction (STEMI)?


The Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) trial included 3,602 patients with STEMI undergoing primary percutaneous coronary intervention who were randomized to heparin plus a glycoprotein IIb/IIIa inhibitor (GPI) (n = 1,802) versus bivalirudin monotherapy (n = 1,800). Stents were implanted in 3,202 patients, including 2,261 who received drug-eluting stents (DES) and 861 who received only bare-metal stents (BMS). All adverse events, including stent thrombosis, were adjudicated by an independent clinical events committee blinded to pharmacology and stent assignment after review of original source documentation. Kaplan-Meier methods were used to derive the event rates at follow-up and to plot time-to-event curves; comparisons were made with the log-rank test.


Definite or probable stent thrombosis within 2 years occurred in 137 patients (4.4%), including 28 acute events (0.9%), 49 subacute events (1.6%), 32 late events (1.0%), and 33 very late events (1.1%). The 2-year cumulative rates of stent thrombosis were 4.4% with both DES and BMS (p = 0.98) and 4.3% versus 4.6% in patients randomized to bivalirudin monotherapy versus heparin plus a GPI, respectively (p = 0.73). Acute stent thrombosis occurred more frequently in patients assigned to bivalirudin compared with heparin plus a GPI (1.4% vs. 0.3%; p < 0.001), whereas stent thrombosis after 24 hours occurred less frequently in patients with bivalirudin compared with heparin plus a GPI (2.8% vs. 4.4%; p = 0.02). Prerandomization heparin and a 600 mg clopidogrel loading dose were independent predictors of reduced acute and subacute stent thrombosis, respectively.


The authors concluded that stent thrombosis is not uncommon within the first 2 years after primary percutaneous coronary intervention in STEMI, and occurs with similar frequency in patients receiving DES versus BMS.


This study suggests that stent thrombosis within 2 years is a relatively common event, occurring in 4.4% of patients, and appears to be evenly distributed among the acute, subacute, late, and very late time periods. Furthermore, the type of stent implanted (DES vs. BMS) was not related to stent thrombosis during any time interval up to 2 years, including very late stent thrombosis; and occurred with similar frequency in patients treated with unfractionated heparin plus GPI and bivalirudin monotherapy. It is possible that optimizing adjunct pharmacology with early antithrombin therapy and preloading with a potent platelet adenosine diphosphate antagonist, may reduce early stent thrombosis and further improve prognosis in these high-risk patients, but this requires further study.

Clinical Topics: Anticoagulation Management, Invasive Cardiovascular Angiography and Intervention

Keywords: Prognosis, Myocardial Infarction, Follow-Up Studies, Thrombosis, Drug-Eluting Stents, Heparin, Hirudins, Percutaneous Coronary Intervention

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