Long-Term Clinical Outcomes of Intracoronary Bolus-Only Versus Intracoronary Bolus Plus Maintenance Intravenous Glycoprotein IIb/IIIa Inhibitor Therapy in Patients with ST-Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Background: Intracoronary (IC) administration of glycoprotein IIb/IIIa inhibitors (GPIs) may enhance local platelet inhibition and myocardial reperfusion during primary percutaneous coronary intervention (PCI). However, whether maintenance intravenous (IV) infusion after an IC GPI bolus provides incremental long-term clinical benefit remains uncertain. Methods: This retrospective, observational, nonrandomized, uncontrolled, real-world, two-center cohort study included 684 consecutive patients with STEMI undergoing primary PCI between 15 March 2015, and 15 March 2018. Patients were classified into three groups according to GPI treatment during the index procedure: no GPI (n = 431), IC bolus-only GPI (n = 53), and IC bolus followed by maintenance IV GPI infusion (n = 200). The primary endpoint was long-term major adverse cardiovascular events (MACE), defined as the first occurrence of all-cause death, recurrent myocardial infarction, repeat coronary revascularization, or stroke; the principal comparison was IC bolus plus IV infusion versus IC bolus-only therapy. Associations with MACE were assessed using extended Cox regression with time-varying coefficients and generalized propensity-score overlap weighting, complemented by landmark and restricted mean survival time (RMST) analyses. Results: During a median follow-up of 8.8 years (95% CI, 8.7–8.9), 340 patients (49.7%) experienced MACE. Crude MACE rates were 49.9% with no GPI, 43.4% with IC bolus-only GPI, and 51.0% with IC bolus plus IV infusion (p = 0.612). In the primary extended Cox model, IC bolus plus IV infusion was not associated with lower MACE compared with IC bolus-only therapy (HR, 1.100; 95% CI, 0.693–1.745; p = 0.686). Neither IC bolus-only therapy (HR, 0.933; 95% CI, 0.601–1.448; p = 0.757) nor IC bolus plus IV infusion (HR, 1.026; 95% CI, 0.803–1.311; p = 0.837) differed significantly from no GPI. Propensity-score overlap weighting substantially improved covariate balance, and the IC bolus plus IV infusion versus IC bolus-only association remained nonsignificant (HR, 1.262; 95% CI, 0.791–2.013; p = 0.330). Results were consistent across secondary multivariable, landmark, RMST, and post-discharge sensitivity analyses. Conclusions: Among patients with STEMI undergoing primary PCI, maintenance IV GPI infusion following an IC bolus was not associated with a statistically significant reduction in long-term MACE compared with IC bolus-only therapy. However, the limited size of the bolus-only group and the resulting wide confidence intervals preclude exclusion of a clinically meaningful benefit or harm. These findings should not be interpreted as demonstrating equivalence between the two strategies.