Review article: Impact of 12-lead electrocardiography system of care on emergency medical service delays in ST-elevation myocardial infarction: A systematic review and meta-analysis.

To assess the impact of prehospital 12-lead electrocardiography (PH ECG) on emergency medical service (EMS) delay in patients with ST-elevation myocardial infarction (STEMI), we systematically searched five online electronic databases, including MEDLINE, Embase, Emcare, Cochrane Library and CINAHL, between 1990 and August 2017. Controlled trials and observational studies comparing EMS time delays with and without PH ECG in STEMI patients were eligible. Two reviewers independently screened studies for eligibility, extracted data and appraised study quality. The primary outcome was the time elapsed between scene arrival and hospital arrival. The secondary outcomes were response time, scene time, transport time and emergency call-to-hospital arrival time. Random effects models were used to pool weighted mean differences in EMS delay. Seven moderate-quality studies (two controlled trials and five observational) involving 81 005 participants were included in the data synthesis. The primary treatment strategy was in-hospital thrombolysis and percutaneous coronary intervention in four and three studies, respectively. PH ECG was associated with a 7.0 min increase in scene arrival-to-hospital arrival time (three studies; n = 80 628; 95% CI 6.7-7.2; I2 = 0.0%) and a 2.9 min increase in scene time (four studies; n = 377; 95% CI 1.2-4.6; I2 = 0.0%). PH ECG had no effect on transport or call-to-hospital intervals, although both measures showed evidence of heterogeneity. In patients with STEMI, PH ECG is associated with a modest increase in EMS delays. Measurement and improvement of EMS system delays may help to expedite treatment for STEMI.