Use of the prehospital ECG improves door-to-balloon times in ST segment elevation myocardial infarction irrespective of time of day or day of week

Background: The use of the prehospital electrocardiogram (ECG) to identify patients with ST-segment elevation myocardial infarction (STEMI), coupled with a centralised system to alert the cardiac catheterisation team in preparation for prompt intervention, has been shown to reduce door-to-balloon times (DBT) effectively. A confounding variable in prolonging the recommended 90 min DBT is the time of day or day of the week of patient presentation. We postulated that use of the prehospital ECG, coupled with an emergency department initiated "Cath Alert'' system, could neutralise DBT delays related to time of day or day of week. Methods: A prospective study was conducted on 167 consecutive patients presenting to our emergency department with acute STEMI. All patients were treated with primary percutaneous coronary intervention. Patients were grouped according to time of presentation: during regular hours (Monday to Friday 08:00 to 17:00) vs off hours (after 17:00 on weekdays and all hours on weekends). Baseline recorded variables included mode of presentation, transmission of prehospital ECG, and activation of Cath Alert system. Results: Overall, the mean (SD) DBT was 69 (35) mins, with the majority of patients (n = 131, 78%) achieving the recommended DBT of 90 mins. The shortest DBT occurred in patients who arrived by emergency medical services with use of the prehospital ECG and Cath Alert system (53 (21) min), while those who arrived as a walk- in without use of emergency medical services had the longest DBT (105 (38) min; p<0.001). Compared to regular hours, presentation during off hours prolonged DBT in patients presenting via emergency medical services (75 (16) vs 53 (18) min, p = 0.03). With transmission of the prehospital ECG, the delay in DBT was improved among those presenting off hours, nullifying the adverse effect of off hour presentation (54 (21) vs 49 (22) min; p = 0.26). Conclusion: Variables such as time of day and mode of presentation have an impact on achieving currently recommended DBT in patients with STEMI. With the addition of each prehospital variable in succession-that is, arrival by emergency medical services, Cath Alert system, and the prehospital ECG-the DBT can be progressively shortened and the adverse "off hour effect'' nullified.