Written by Clark Strunk
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In this single-center RCT of patients with STEMI within 6 hours of symptom onset, a heparin bolus at first prehospital medical contact (FMC) resulted in better flow in the infarct related artery (IRA) at initial angiography, without an increased risk of significant bleeding.
Early bird gets the heparin…
This was a single-center, open-label, randomized trial in 593 STEMI patients (within 6 hours of symptom onset) to receive 70–100 units/kg of unfractionated heparin (UFH) at FMC vs. after initial angiography and before primary PCI. The primary endpoint was TIMI 2 or 3 flow in the IRA at initial angiography (which has previously been associated with improved clinical outcomes). This was seen in 43% of patients in the early UFH group vs. 27% in the control (RR 1.59, 95%CI 1.27–1.98). There was no difference in significant bleeding using the Bleeding Academic Research Consortium (BARC) scale. In the prehospital UFH group, there was also earlier ST-resolution and lower troponin levels at 24 hours but no differences in peak troponin, incidence of cardiac arrest, development of cardiogenic shock, or 30-day mortality.
How will this change my practice?
This will not directly change my practice. It used a surrogate outcome. Previous data are conflicting. It also requires strict timing from symptom onset and ECG overread by a cardiologist, which makes me think prehospital heparin is not quite ready yet for broad implementation. It underscores that coronary occlusions are dynamic, propagate, and resolve, and earlier administration of antiplatelets and anticoagulation may be beneficial by promoting clot lysis and improving coronary flow earlier, which could reduce infarct size, improve cardiac function, and improve long term survival. However, in my view, this is yet to be proven.
Source
HEPARIN STEMI Study. Prehospital Heparin Administration in Patients With STEMI Undergoing Primary PCI: HEPARIN STEMI Randomized Controlled Trial. Circulation. 2026 Mar 30. doi: 10.1161/CIRCULATIONAHA.126.079839. Epub ahead of print. PMID: 41910504.
