Alain Tanguay, MD, Eric Brassard, MD, Johann Lebon, PhD, François Bégin, MD, Denise Hébert, BcSc-Infa, and Jean-Michel Paradis, MD

The aim of the study was to determine the prevalence of false-positive and inappropriate cardiac catheterization laboratory (CCL) activation in patients suspected with ST-elevation myocardial infarction (STEMI) diverted to a percutaneous coronary intervention (PCI) facility after paramedics wireless 12-lead electrocardiogram transmission to an emergency physician at an online medical control center. This retrospective study collected data from medical records of patients with suspected STEMI from 2006 to 2014. It included demographics, coronaropathic risk factors, cardiac biomarkers, time from the first medical contact to treatment, and final diagnosis. Primary outcome was the rate of false-positive and inappropriate CCL activation. As secondary outcomes, we compared patient characteristics between cases of appropriate and inappropriate CCL activation, and we assessed the presence of cardiac biomarkers, time from first medical contact to start of PCI, and final diagnosis. Overall, 673 patients with suspected STEMI were included in the analysis. A total of 640 patients (95%) had coronarography, of which 10% (62 of 640) did not have a culprit coronary artery (false positive). Angiography was canceled for 5% (33 of 673) of patients. The total false-positive and inappropriate CCL activation rate was 14% (95 of 673). Average time from the first medical contact to the start of PCI was 47 – 18.1 minutes. Unwanted CCL activations were more likely to involve men aged >65 years and patients with a history of coronary artery disease. In conclusion, our system of transmitted pre-hospital electrocardiography and STEMI interpretation by emergency physicians at an online medical control center showed a total false-positive and inappropriate CCL activation rate of 14% over the 8-year study period.


In accordance with the American Heart Association and the American College of Cardiology guidelines1e3 and to improve prehospital cardiac triage and assessment of patients with suspected ST-segment elevation myocardial infarction (STEMI), modern health care systems have developed numerous strategies that incorporated the use of prehospital 12-lead electrocardiogram (ECG).4,5 In the Chaudière-Appalaches and Québec City regions of Québec (Canada), a model emergency medical services (EMS) system was introduced in 2006. This system involves wireless transmission of a prehospital 12-lead ECG by paramedics for interpretation by an emergency physician (EP) at a regional online medical control (OLMC) center.6 Even if the use of ECG has proven to improve long-term survival and decrease complication rates, the rate of inappropriate and false-positive cardiac catheterization laboratory (CCL) activations in this system is unknown. The main objective of this study was to determine rates of false-positive and inappropriate CCL activation after implementation of a model EMS system of STEMI care in the Chaudière-Appalaches and Québec City regions.

Methods

This study was approved by the Research Ethics Committee of the Centre de Recherche de l’Hôtel-Dieu de Lévis (Lévis, Québec). We performed a retrospective analysis of medical records from a regional OLMC center (Unité de Coordination Clinique des Services Préhospitaliers d’Urgence [UCCSPU], Lévis, Québec), a 24/7 PCI facility (Institut Universitaire de Cardiologie et de Pneumologie de Québec [IUCPQ], Québec City, Québec), and EMS. UCC-SPU is located in an academic hospital (Hôtel-Dieu de Lévis) and acts as an EMS coordination unit, providing online medical support and assistance to basic life support (BLS) emergency medical technicians (EMTs) in Québec City and Chaudière-Appalaches including a pain management program7 and prehospital STEMI detection program.8

The UCCSPU prehospital STEMI detection program was implemented in the Chaudière-Appalaches region in 2006 and in the greater Québec City area in 2012. This program was designed to identify rapidly all field’s patients with chest pain (especially those with suspected STEMI) and determine if they should be transported to a local hospital or diverted to a PCI facility, based on ECG’s interpretation and on established guidelines regarding door-to-balloon time and reperfusion delay2 (Figure 1). BLS-EMTs evaluated field’s patients using specific protocols based on the presenting complaint and condition. If the patient presents with complaints such as thoracic or abdominal pains, difficulty breathing, hypotension or hypertension, or abnormal pulse, the BLS-EMT wirelessly transmits a 12-lead ECG to the OLMC center.8

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