Prehospital Administration of Unfractionated Heparin in ST-Segment Elevation Myocardial Infarction Is Associated With Improved Long-Term Survival

OBJECTIVE: Administration of unfractionated heparin to STEMI patients by the ambulance service is an established practice in Scotland, but the efficacy is unknown. We studied the effects of unfractionated heparin in STEMI patients treated by primary percutaneous coronary intervention, on infarct artery patency and mortality. METHODS AND RESULTS: Consecutive patients (n = 1000) admitted to Ninewells Hospital, Dundee, from 2010 to 2014 for primary percutaneous coronary intervention were allocated to 2 groups: 437 (44%) prehospital heparin (PHH) administered by paramedics, and 563 (56%) in-hospital heparin. A trained medical student assessed coronary flow at presentation and collected the data. Mortality status was ascertained at 30 days and 5 years. Cox proportional hazards regression models were generated. The patient groups were similar, although PHH had shorter symptom onset-treatment time (187 vs. 251 minutes, P < 0.001) and less cardiogenic shock (3.9% vs. 8.0%, P = 0.008). Initial coronary flow was not different between the groups. Thirty day mortality in PHH was 2.5% versus 8.3%, P < 0.001. Independent predictors of 30-day mortality were age (odds ratio 1.07, 95% CI 1.04-1.09), cardiogenic shock (5.97, 3.33-10.69), radial access (0.53, 0.28-0.98), and PHH (0.33, 0.17-0.66). Five-year mortality in PHH was 13.0% versus 21.6%, P < 0.001. Significant predictors of long-term mortality were age (1.07, 1.06-1.09), cardiogenic shock (3.40, 2.23-5.17), and PHH (0.68, 0.49-0.96). CONCLUSIONS: PHH was associated with reduced short- and long-term mortality after adjusting for important potential confounders.