Introduction: Prior data from our institution suggested that our paramedics can accurately interpret ST-segment elevation myocardial infarction (STEMI) on prehospital 12-lead electrocardiograms (ECGs), and that activation of the cardiac catheterization laboratory by paramedics immediately upon diagnosing STEMI at the scene could potentially decrease door-to-balloon (D2B) times. A "field activation" protocol was thus initiated in May 2010. This study examined D2B times and compliance with the national 90-minute D2B performance benchmark in the first 14 months. Hypothesis. We hypothesized that D2B times would be shorter, and 90-minute compliance better, when the catheterization laboratory was activated by emergency medical services (EMS), compared with when either EMS failed to activate the catheterization laboratory or when the STEMI patient arrived by means other than EMS.
Methods: For this prospective, observational study, EMS and hospital data were reviewed for consecutive STEMI patients at a single hospital between May 2010 and July 2011. Patients were categorized as: 1) EMS field activations, 2) patients transported by EMS without EMS catheterization laboratory activation (e.g., ambulance from outside our area, paramedic missed STEMI/protocol violation), or 3) walk-in STEMI patient. Data were manipulated in Excel, means with standard deviations (SDs) and 95% confidence intervals (95% CIs) were determined, and analysis of variance (ANOVA) with Dunnett's correction was used to compare groups.
Results: There were 38 EMS field activations, 47 nonactivation EMS STEMI arrivals, and 28 walk-in STEMI patients. The mean (±SD) D2B times were 37 (±17), 87 (±40), and 80 (±23) minutes, respectively. D2B time was better for the EMS field activations than for either nonactivation EMS transports (difference of means 35.3 min, 95% CI 22.3-48.3 min, p < 0.001) or walk-in patients (difference of means 37.0 min, 95% CI 21.8-52.2 min, p < 0.001). Compliance with the 90-minute D2B benchmark was 100%, 72%, and 68%, respectively, and was better for the EMS field activations than for either of the other groups (p < 0.001).
Conclusions: In the system studied, EMS field activation of the catheterization laboratory for patients with STEMI is associated with shorter D2B times and better compliance with 90-minute benchmarks than ED activation for either walk-in STEMI patients or STEMI patients arriving by EMS without field activation. Improvements are needed in compliance with the field activation protocol to maximize these benefits. Key words: emergency medical services; emergency medical technicians; electrocardiography; myocardial infarction; heart catheterization.