Prehospital heparin loading in patients with suspected non-ST-segment elevation acute coronary syndrome

Jonas Sundermeyer (Hamburg)1, A. Schock (Hamburg)1, C. Kellner (Hamburg)1, N. A. Sörensen (Hamburg)2, P. Haller (Hamburg)1, J. Lehmacher (Hamburg)3, N. Thießen (Hamburg)1, B. Toprak (Hamburg)1, R. Twerenbold (Hamburg)1, S. Blankenberg (Hamburg)1, T. Zeller (Hamburg)1, P. M. Clemmensen (Hamburg)1, J. T. Neumann (Hamburg)3

1Universitäres Herz- und Gefäßzentrum Hamburg Klinik für Kardiologie Hamburg, Deutschland; 2Universitäres Herz- und Gefäßzentrum Hamburg Klinik und Poliklinik für Kardiologie Hamburg, Deutschland; 3Universitäres Herz- und Gefäßzentrum Hamburg Allgemeine und Interventionelle Kardiologie Hamburg, Deutschland


Background: Prehospital care is an important part of the acute treatment of myocardial infarction (MI).

Although pre-treatment with antithrombotic therapies has changed over the past decade, there is still a lack of clear evidence supporting pre-hospital heparin administration in patients with suspected non-ST-segment elevation acute coronary syndrome (NSTE-ACS).

Purpose: This study aimed to evaluate if pre-hospital heparin administration by emergency medical service improves clinical outcome in patients with suspected NSTE-ACS.

Methods: In this observational study, patients with suspected MI presenting to the emergency department of a German tertiary centre were prospectively enrolled. Patients with ST-segment elevation MI were excluded. Patients with and without prehospital heparin administration were compared using propensity score matching for the variables age, hypertension, current smoking status, history of coronary artery disease and ischemic signs in electrocardiogram. The association between pre-hospital heparin loading with 30-day and 1-year mortality was assessed using Kaplan-Meier estimations and Cox regression models.

Results: A total of 2,545 patients were available and pre-hospital heparin was administered in 507 (19.9%) patients. In the unmatched cohort, mean age was 64 years and 1620 (63.7%) of the patients were male. A total of 1659 (65.4%) patients presented with known hypertension, 321 (12.7%) had diabetes, and 556 (22.3%) were current smokers. Overall, 858 (33.7%) patients had a known history of coronary artery disease. Compared to patients without pre-hospital heparin administration, those pre-treated with heparin in the unmatched cohort were older (69 vs. 63 years) and less frequently male (23% vs. 33%), more often active smokers (26.3% vs. 21.3%) and had higher rates of prior coronary revascularization (19.7% vs. 10.7%).

After propensity matching, 483 patients with pre-hospital heparin administration were compared to 483 patients without pre-hospital heparin administration. Importantly, there was no difference in 30-day mortality (no-heparin 0.21% vs. heparin 0.41%, adjusted hazard ratio 1.67, CI 0.22-18.23, p=0.615, Figure 1a) and 1-year mortality (no-heparin 5.2% vs. heparin 5.4%, adjusted hazard ratio 1.04, CI 0.60-1.79, p=0.900, Figure 1b). Bleeding events during the hospital course occurred at a low frequency (<1%) and were not different between groups.

Conclusion: In this propensity-score matched study, the use of pre-hospital heparin administration by emergency medical service was not associated with improved clinical outcome in patients presenting with suspected NSTE-ACS. These findings question the commonly practiced pre-hospital parenteral anticoagulation therapy in this patient population and might potentially warrant a more restricted utilization pending in-hospital risk assessment.

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