The Utility of Prehospital ECG Transmission in a Large EMS System.

Background: Prehospital identification of STEMI and activation of the catheterization lab can improve door-to-balloon (D2B) times but may lead to decreased specificity and unnecessary resource utilization. The purpose of this study was to examine the effect of electrocardiogram (ECG) transmission on false-positive (FP) cath lab activations and time to reperfusion.

Methods: This is a retrospective cohort from a registry in a large metropolitan area with regionalized cardiac care and emergency medical services (EMS) with ECG transmission capabilities. Thirty-four designated STEMI receiving centers (SRC) contribute to this registry, from which patients with a prehospital ECG software interpretation of myocardial infarction (MI) indicated by ****Acute MI****, or manufacturer equivalent, were identified between April 2011 and September 2013. Frequency of FP field activations (defined as not resulting in emergent percutaneous coronary intervention [PCI] or referral for CABG during hospital admission) for patients with ECG transmission received by the SRC was compared to a reference group without successful ECG transmission. FP field activations were compared to the baseline frequency of FP ED activations. We hypothesized that successful transmission would reduce FP field activation to ED activation levels. Door-to-balloon and first medical contact-to-balloon (FMC2B) times were compared. The protocol for field cath lab activation varied by institution.

Results: There were 7,768 patients presenting with a prehospital ECG indicating MI. The ECG was received by the SRC for 2,156 patients (28%). Regardless of transmission, the cath lab was activated 77% of the time; this activation occurred from the field in 73% and 74% of the activations in the transmission and reference group, respectively. The overall proportion of FP activation was 57%. Among field activations, successful ECG transmission reduced the FP activation rate compared to without ECG transmission, 55% vs. 61% (RD = -6%, 95%CI -9, -3%). This led to an overall system reduction in FP activations of 5% (95%CI 2, 8%). ECG transmission had no effect on D2B and FMC2B time.

Conclusion: Prehospital ECG transmission is associated with a small reduction in false-positive field activations for STEMI and had no effect on time to reperfusion in this cohort.