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


South Atlantic


Grand Strand Medical Center

Document Type


Publication Date



Emergency Department, NSTEMI, STEMI, acute myocardial infarction, circadian, daily, diurnal, seasonal


Cardiology | Cardiovascular Diseases | Emergency Medicine | Internal Medicine


BACKGROUND: Previous studies show that myocardial infarctions (MIs) occur most frequently in the morning.

OBJECTIVES: 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.

METHODS: 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.

RESULTS: 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, which held true for both subtypes (MI 26.7%, STEMI 26.4%, NSTEMI 26.7%).

CONCLUSIONS: These data suggest a potential shift in the circadian pattern of MI, revealing an afternoon predominance for both STEMI and NSTEMI subtypes.

Publisher or Conference

Journal of Emergency Medicine