Presentation Times of Myocardial Infarctions to the Emergency Department: Disappearance of the Morning Predominance.

Abstract

Previous studies show that myocardial infarctions (MIs) occur most frequently in the morning. We hypothesized that there no longer is a morning predominance of MI, and that the timing of ST-elevation myocardial infarction (STEMI) vs. non-ST-elevation myocardial infarction (NSTEMI) presentation differs. We reviewed MI, STEMI, and NSTEMI patients (2013-2017) from a multiple-hospital system, identified by diagnostic codes. Daily emergency department arrival times were categorized into variable time intervals for count and proportional analysis, then examined for differences. There were 18,663 MI patients from 12 hospitals included in the analysis. Most MIs occurred between 12:00 pm and 5:59 pm (35.7%), and least between 12:00 am-5:59 am (16.3%). After subdividing all MIs into STEMIs and NSTEMIs, both groups continued to have the greatest presentation between 12:00 pm and 5:59 pm (33.1% and 36.0%, respectively). STEMIs (17.2%) and NSTEMIs (16.2%) were least frequent between 12:00 am and 5:59 am. We found the second most common presentation time for MIs was in the 6 pm-11:59 pm time period, whichheld true for both subtypes (MI 26.7%, STEMI 26.4%, NSTEMI 26.7%). These data suggest a potential shift in the circadian pattern of MI, revealing an afternoon predominance for both STEMI and NSTEMI subtypes.