Association of pre-hospital time intervals and clinical outcomes in ST-elevation myocardial infarction patients

Study Objectives Timely coronary reperfusion is critical for favorable outcomes after ST-elevation myocardial infarction (STEMI). A substantial proportion of the total ischemic time is patient related, occurring before first medical contact (FMC). We aimed to expand the limited current understanding of the associations between prehospital intervals and clinical outcomes. Methods We conducted a retrospective analysis of consecutive STEMI patients who underwent primary percutaneous coronary intervention (pPCI) (January 2009-March 2016) and assessed the associations between prehospital intervals and the incidence of new heart failure, cardiogenic shock, and hospital length of stay (LOS), adjusting for important clinical variables. Results A total of 773 patients (77% men, median age 65 years) met eligibility criteria. The median pre-911 activation interval was 29 minutes (interquartile range: 11, 89); the median 911 call to FMC interval was 12 minutes (interquartile range: 9, 15). In multivariable analysis, there was a V-shaped relationship between the pre-911 activation interval and outcomes: a lower likelihood of new heart failure (odds ratio [OR] 0.51; 95% confidence interval [CI]: 0.30, 0.87), cardiogenic shock (OR 0.40; 95% CI: 0.21, 0.75) and prolonged LOS (OR 0.24; 95% CI: 0.14, 0.42) for midrange intervals (11-88 minutes) when compared to the early (< 11-minute) interval. There was no statistically significant relationship between total pre-FMC time and FMC to device activation time. Conclusions Among ambulance-transported STEMI patients receiving pPCI, the shortest and longest pre-911 activation time intervals were associated with poorer outcomes. However, variation in post-FMC interval alone was not associated with outcomes, suggesting that interventions to reduce pre-FMC intervals must be prioritized.