Objective: Repeated or serial 12-lead electrocardiograms (ECGs) in the prehospital setting may improve management of patients with subtle ST-segment elevation (STE) or with a ST-segment elevation myocardial infarction (STEMI) that evolves over time. However, there is a minimal amount of scientific evidence available to support the clinical utility of this method. Our objective was to evaluate the use of serial 12-lead ECGs to detect STEMI in patients during transport in a Canadian emergency medical services (EMS) jurisdiction.
Methods: We performed a retrospective study of suspected STEMI patients transported by EMS in the Chaudière-Appalaches region (Québec, Canada) between August 2006 and December 2013. Patients were monitored by a serial 12-lead ECG system where an averaged ECG was transmitted every 2 minutes. Following review by an emergency physician, ECGs were grouped as having either a persistent STE or a dynamic STE that evolved over time.
Results: A total of 754 suspected STEMI patients were transported by EMS during the study period. Of these, 728 patients met eligibility criteria and were included in the analysis. A persistent STE was observed in 84.3% (614/728) of patients, while the remaining 15.7% (114/728) had a dynamic STE. Among those with dynamic STE, 11.1% (81/728) had 1 ST-segment change (41 no-STEMI to STEMI; 40 STEMI to no-STEMI) and 4.5% (33/728) had ≥ 2 ST-segment changes (17 no-STEMI to STEMI; 16 STEMI to no-STEMI). Overall, in 8.0% (58/728) of the cohort, STEMI was identified on a subsequent ECG following an initial no-STEMI ECG.
Conclusions: Through recognition of transient ST-segment changes during transport via the prehospital serial 12-lead ECG system, STEMI was identified in 8% of suspected STEMI patients who had an initial no-STEMI ECG. Key words: electrocardiography; emergency medical services; ST-elevation myocardial infarction; prehospital dynamic ECG.