Pre-hospital heparin is not associated with infarct vessel patency and mortality in ST-segment elevation myocardial infarction patients with out-of-hospital cardiac arrest.

BACKGROUND: Pre-hospital heparin administration has been reported to improve prognosis in patients with out-of-hospital cardiac arrest (OHCA). This beneficial effect may be limited to the subgroup of ST-segment elevation myocardial infarction (STEMI) patients.

METHODS: To assess the impact of pre-hospital heparin loading on TIMI (Thrombolysis in Myocardial Infarction) flow grade and mortality in STEMI patients with OHCA, we analyzed data from 2,566 consecutive patients from two hospitals participating in the prospective Feedback Intervention and Treatment Times in ST-segment Elevation Myocardial Infarction (FITT-STEMI) trial.

RESULTS: In 394 participants with OHCA, 272 (69%) received heparin from the emergency medical service (EMS). Collapse witnessed by EMS (odds ratio (OR) = 3.53, 95%-confidence interval (CI) = 1.54-8.09; p = 0.003) and pre-hospital ECG recording (OR = 3.32, 95% CI = 1.06-10.35; p = 0.039) were identified as parameters significantly associated with pre-hospital heparin use. In univariate analysis, in-hospital mortality was lower in the group receiving heparin in the pre-hospital setting (26.8% vs. 42.6%, p = 0.002). However, in a regression model, pre-hospital heparin use was no longer a significant predictor of mortality (OR = 0.992; p = 0.981). Patency of the infarct artery prior to coronary revascularization, as measured by TIMI flow grade, was not associated with pre-hospital administration of heparin in OHCA patients (OR = 0.840; p = 0.724).

CONCLUSIONS: In STEMI patients with OHCA, pre-hospital use of heparin is neither associated with improved early patency of the infarct artery nor with a better prognosis. Our results do not support the assumption of a positive effect of heparin administration in the pre-hospital treatment phase in STEMI patients with OHCA.

TRIAL REGISTRATION: ClinicalTrials.gov: NCT00794001.