Pre-hospital admission of heparin in patients with suspected non-ST segment elevation acute coronary syndrome.

Background: Evidence supporting pre-hospital heparin administration in patients with suspected non-ST segment elevation acute coronary syndrome (NSTE-ACS) is lacking. We aim to evaluate if pre-hospital heparin administration by emergency medical service improves clinical outcome in patients with suspected NSTE-ACS.

Methods: Patients with suspected myocardial infarction (MI) presenting to the emergency department were prospectively enrolled from 2013 to 2021, excluding those with ST segment elevation MI. Patients with and without prehospital heparin administration were compared using propensity score matching. To assess the association between pre-hospital heparin loading, 30-day and 1-year mortality, Kaplan-Meier estimations and Cox regression models were used.

Results: Among 1,234 patients, median age was 69 years, 755 (61.2%) were male, 867 (70.5%) with known hypertension, 177 (14.4%) had diabetes, 280 (23.1%) were current smokers, and 444 (36.0%) had a history of CAD. Compared to patients without pre-hospital heparin administration, heparin pre-treated patients were more often active smokers (26.5% vs. 20.8%). After propensity matching, 475 patients with vs. without pre-hospital heparin administration were compared, with no significant difference in 30-day mortality (no-heparin 1.3% vs. heparin 0.4%) and 1-year mortality (no-heparin 7.2% vs. heparin 5.5%, adjusted HR 0.98, CI 0.95-1.01, p = 0.22). Bleeding events occurred at a low frequency (< 2%) and did not differ between groups.

Conclusions: In this study, pre-hospital heparin administration was not associated with improved clinical outcome in patients with suspected NSTE-ACS. These findings question pre-hospital heparin therapy in this patient population and might potentially warrant a more restricted utilization pending in-hospital risk assessment.