Excess Heparin Dosing Among Fibrinolytic-treated Patients with ST-Segment Elevation Myocardial Infarction

Background: Although the use of heparin with fibrinolytics is associated with more rapid ST-segment resolution and increased infarct-related artery patency among patients with ST-segment elevation myocardial infarction (STEMI), its associated increase in bleeding risk is well documented and might be augmented by excess heparin dosing. Methods: We sought to characterize the incidence and associated bleeding risk of excess heparin dosing among patients with STEMI treated with fibrinolysis who were enrolled in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines initiative. Excess dosing was defined as a bolus more than 60 U/kg or an infusion more than 12 U/kg/h per American College of Cardiology/American Heart Association guidelines and was further stratified into major and mild excess (major defined as a bolus > 70 U/kg or infusion >15 U/kg/h). Results: Among 964 fibrinolytic-treated patients with STEMI, 758 (79%) received adjunctive unfractionated heparin therapy. Of these, 368 patients (49%) received excess dosing of unfractionated heparin and 137 patients (18%) received major excess heparin dosing. Factors significantly associated with excess dosing included low body weight and female sex. Patients who received major excess dosing had higher unadjusted rates of major bleeding (19.2% vs 12.4%, P = .004) and transfusion (13.5% vs 4.7%, P = .0002) than patients without excess dosing. After adjustment, a trend persisted for the association with higher transfusion risk (odds ratio 1.39 [0.61-3.14]). Conclusion: Approximately half of fibrinolytic-treated patients with STEMI in contemporary practice received an excess dose of unfractionated heparin. Careful attention to dosing is needed to limit the compounded bleeding risk when heparin is added to fibrinolytic therapy.