Prehospital Heparin Administration in Patients With STEMI Undergoing Primary PCI: HEPARIN STEMI Randomized Controlled Trial

Circulation, Ahead of Print. Background: Primary PCI is the preferred reperfusion strategy in patients with ST-elevation myocardial infarction (STEMI).

We investigated benefits and safety of pretreatment with unfractioned heparin (UFH) in STEMI referred to primary PCI.Methods: Our single-center, open-label, randomized controlled trial assigned STEMI with ≤6 hours of symptom duration either to 70-100 IE/kg bolus of UFH at first prehospital medical contact (FMC) plus supplemental dose before PCI adjusted to activated clothing time ≥250 seconds or to control group undergoing standard UFH at the time of PCI. Primary efficacy endpoint was TIMI 2-3 flow in infarct related artery (IRA) at initial coronary angiography.

Primary safety endpoint was BARC 3-5 bleeding during the index hospital stay.Results: From March 2022 to February 2025, 298 patients were randomized to UFH pretreatment and 295 to the control group. Both groups were comparable in age, gender, risk factors, previous cardiovascular events and median delay from symptoms to coronary angiography (145 min vs 150 min; p=0.814).

Median time from UFH pretreatment to coronary angiography was 60 min (25thand 75thIQR 47 - 55 min). TIMI 2-3 in IRA was documented in 43% in UFH pretreatment and 27% in control groups (RR 1.59 [95% CI 1.27-1.98]; p<0.001) without significant difference in BARC 3-5 bleeding (2.4% vs 2.0%; RR 1.16 [95% CI 0.39-3.45]; p=0.789).Conclusions: In patients with STEMI undergoing primary PCI in a mature STEMI network, pretreatment with UFH at FMC was associated with an absolute 16% increase in IRA patency without causing excessive bleeding.