Early Versus Deferred Unfractionated Heparin in STEMI Undergoing Primary PCI

Background: Early restoration of infarct-related artery patency before primary percutaneous coronary intervention (PCI) may improve outcomes in patients with ST-segment elevation myocardial infarction (STEMI). However, the clinical value of preprocedural unfractionated heparin administration remains uncertain. Methods: We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) and propensity score-matched (PSM) studies comparing preprocedural unfractionated heparin administration before primary PCI versus standard in-hospital anticoagulation. Random-effects models were used to estimate pooled risk ratios (RRs) and 95% confidence intervals (CIs). The primary angiographic outcomes were initial TIMI 2-3 flow and final TIMI 3 flow. Clinical outcomes included short-term mortality and major bleeding. Results: We included 6 studies (4 RCTs and 2 PSM cohorts) comprising 5,789 patients. The study population was predominantly male (72.0%-82.0%), aged 57 to 65 years, with radial access utilized in 70.6% to 95.8% of contemporary procedures. Early heparin significantly increased the likelihood of initial TIMI 2-3 flow before PCI (RR 1.29, 95% CI 1.09-1.53; p=0.003; I 2 =43%). No significant difference was observed in final TIMI 3 flow (RR 1.01, 95% CI 0.99-1.03; I 2 =0%). Early heparin was not associated with lower short-term mortality (RR 0.93, 95% CI 0.72-1.19; I 2 =0%) or major bleeding (RR 0.94, 95% CI 0.56-1.59; I 2 =40%). Conclusions: Among patients with STEMI undergoing primary PCI, early unfractionated heparin improved preprocedural coronary patency but did not improve final reperfusion or short-term mortality. Importantly, early administration was not associated with an increased risk of major bleeding.