Early reperfusion remains the main prognostic determinant in patients with ST-segment elevation myocardial infarction (STEMI). Although primary percutaneous coronary intervention (PCI) is the treatment of choice, achieving patency of the infarct-related artery before the procedure has been associated with smaller infarct size and improved clinical outcomes. In this context, the optimal timing for administering unfractionated heparin (UFH) remains a matter of debate.
The HEPARIN-STEMI study was a randomized, open-label, single-center trial that enrolled 593 patients presenting with STEMI within 6 hours of symptom onset. Participants were randomly assigned to receive an intravenous bolus of UFH (70–100 IU/kg) at the first prehospital medical contact or according to the conventional strategy of administration at the beginning of primary PCI. The primary efficacy endpoint was the presence of TIMI 2/3 flow in the infarct-related artery before PCI, while the primary safety endpoint was the occurrence of BARC 3–5 major bleeding during hospitalization.
Early UFH administration significantly increased the initial patency of the culprit artery, with TIMI 2–3 flow observed in 43% of patients compared with 27% in the control group (RR 1.59; 95% CI: 1.27–1.98; p<0.001), representing an absolute 16% increase in spontaneous reperfusion before PCI. This benefit was achieved without prolonging reperfusion times.
Read also: SAPIEN 3 TAVI Durability: Ten-Year Follow-Up in Intermediate-Risk Patients.
From a safety perspective, early treatment did not increase the risk of major bleeding, which occurred in 2.4% of patients receiving prehospital UFH and 2.0% of those treated according to the conventional strategy (RR 1.16; 95% CI: 0.39–3.45; p=0.789). These findings reinforce that early anticoagulation can be implemented safely, without a clear association with an increased risk of hemorrhagic events when incorporated into a primary PCI protocol.
Conclusions: Prehospital heparin improves early reperfusion without increasing bleeding risk
The HEPARIN-STEMI study demonstrates that administering unfractionated heparin at the first medical contact significantly improves the initial patency of the infarct-related artery without increasing the risk of major bleeding. This is a simple, widely available, and low-cost intervention that enhances early reperfusion and provides new evidence supporting its routine use in patients with STEMI undergoing primary PCI.
Original Title: Prehospital Heparin Administration in Patients With STEMI Undergoing Primary PCI: HEPARIN-STEMI Randomized Controlled Trial.
Reference: Fister M, Noc M, Radsel P, Bunc M, Franco D, Goslar T; HEPARIN-STEMI Trial. Prehospital Heparin Administration in Patients With STEMI Undergoing Primary PCI: HEPARIN-STEMI Randomized Controlled Trial. Circulation. 2026 May 19;153(20):1526-1534. doi: 10.1161/CIRCULATIONAHA.126.079839. Epub 2026 Mar 30. PMID: 41910504.
