Impact of emergency medical service delays on time to reperfusion and mortality in STEMI

OBJECTIVES: To explore the relationship between emergency medical service (EMS) delay time, overall time to reperfusion and clinical outcome in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). METHODS: This was a retrospective observational study of 2976 patients with STEMI who presented to EMS and underwent PPCI between January 2014 and December 2017. We performed multivariable logistic models to assess the relationship between EMS delay time and 30-day mortality and to identify factors associated with system delay time. RESULTS: EMS delay time accounted for the first half of total system delay (median=59 min (IQR=48–77)). Compared with those who survived, those who died had longer median EMS delay times (59 (IQR=11–74) vs 74 (IQR=57–98), p<0.001). EMS delay time was independently associated with a higher risk of mortality (adjusted OR 1.20; 95% CI 1.02 to 1.40, for every 30 min increase), largely driven by complicated patients with cardiogenic shock or cardiac arrest. Independent predictors of longer EMS delay times were older age, women, cardiogenic shock, cardiac arrest, prehospital notification and intensive care management. Although longer EMS delay times were associated with shorter door-to-balloon times, total system delay times increased with increasing EMS delay times. CONCLUSION: Increasing EMS delay times, particularly those result from haemodynamic complications, increase total time to reperfusion and are associated with 30-day mortality after STEMI. All efforts should be made to monitor and reduce EMS delay times for timely reperfusion and better outcome.