Effect of Switching Antithrombin Agents for Primary Angioplasty in Acute Myocardial Infarction: The HORIZONS-SWITCH Analysis

Study Questions:

What are the clinical outcomes of switching to bivalirudin after initial administration of heparin in patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI)?


The investigators analyzed the outcomes of the 2,357 patients from the HORIZONS-AMI trial who were treated with unfractionated heparin (UFH) before enrollment according to their subsequent randomization to bivalirudin (switch group, n = 1,178) or UFH plus a glycoprotein IIb/IIIa inhibitor (control group, n = 1,179). Principal endpoint definitions included major adverse cardiac events (death, reinfarction, target vessel revascularization for ischemia, or stroke), major bleeding unrelated to coronary artery bypass graft (CABG) surgery, and net adverse clinical events (NACEs) (major adverse cardiac events or non-CABG surgery major bleeding).


At 30 days, major bleeding occurred in 7.6% of the switch group versus 12.3% of the control group (p = 0.0001). Switch patients had lower 30-day rates of cardiac mortality (1.6% vs. 2.9%, p = 0.04). At 2-year follow-up, switch patients experienced lower rates of major bleeding (8.4% vs. 13.0%, p = 0.0003), cardiac mortality (2.3% vs. 3.8%, p = 0.04), and reinfarction (4.0% vs. 7.1%, p = 0.0002). Two-year rates of definite/probable stent thrombosis were similar in switch and control patients (3.1% vs. 4.3%, p = 0.17).


The authors concluded that in STEMI patients who receive early treatment with UFH, switching to bivalirudin before PPCI results in reduced rates of major bleeding and improved early and late cardiac survival.


The present study suggests that bivalirudin may be safely administered in STEMI even if the activated clotting time from a previous UFH bolus is elevated, and results in reduced hemorrhagic complications, thrombocytopenia, and reinfarction, with improved early and late cardiac survival and freedom from NACEs compared with the alternative of continuing UFH and starting a glycoprotein inhibitor. Although this substudy of the HORIZONS-AMI trial should be considered exploratory and hypothesis generating due to limited statistical power, the data do provide some reassurance regarding the strategy of switching from UFH to bivalirudin for PPCI.

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Aortic Surgery

Keywords: Myocardial Infarction, Follow-Up Studies, Thrombosis, Coronary Artery Bypass, Angioplasty, Thrombocytopenia, Percutaneous Coronary Intervention

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