Early cardiac catheterization laboratory activation by paramedics for patients with ST-segment elevation myocardial infarction on prehospital 12-lead electrocardiograms.

Background: Prompt reperfusion in ST-segment elevation myocardial infarction (STEMI) saves lives. Although studies have shown that paramedics can reliably interpret STEMI on prehospital 12-lead electrocardiograms (p12ECGs), prehospital activation of the cardiac catheterization laboratory by emergency medical services (EMS) has not yet gained widespread acceptance.

Objective: To quantify the potential reduction in time to percutaneous coronary intervention (PCI) by early prehospital activation of the cardiac catheterization laboratory in STEMI.

Methods: This prospective, observational study enrolled all patients diagnosed with STEMI by paramedics in a mid-sized regional EMS system. Patients were enrolled if: 1) the paramedic interpreted STEMI on the p12ECG, 2) the Acute Cardiac Ischemia Time-Insensitive Predictive Instrument (ACI-TIPI) score was 75% or greater, and 3) the patient was transported to either of two area PCI centers. Data recorded included the time of initial EMS "STEMI alert" from the scene, time of arrival at the emergency department (ED), and time of actual catheterization laboratory activation by the ED physician, all using synchronized clocks. The primary outcome measure was the time difference between the STEMI alert and the actual activation (i.e., potential time savings). The false-positive rate (patients incorrectly diagnosed with STEMI by paramedics) was also calculated and compared with a locally accepted false-positive rate of 10%.

Results: Twelve patients were enrolled prior to early termination of the study. The mean and median potential time reductions were 15 and 11 minutes, respectively (range 7-29 minutes). There was one false STEMI alert (8.3% false-positive rate) for a patient with a right bundle branch block who subsequently had a non-ST-segment elevation myocardial infarction. The study was terminated when our cardiologists adopted a prehospital catheterization laboratory activation protocol based on our initial data.

Conclusion: Important reductions in time to reperfusion seem possible by activation of the catheterization laboratory by EMS from the scene, with an acceptably low false-positive rate in this small sample. This type of clinical research can inform multidisciplinary policies and bring about meaningful clinical practice changes.