For Best Outcomes: Have Your MI During Normal Business Hours

Abstract & Commentary

By Andrew D. Perron, MD, FACEP, FACSM Dr. Perron is Residency Program Director, Department of Emergency Medicine, Maine Medical Center, Portland, ME. Dr. Perron has reported no relationships with companies having ties to the field of study covered by this CME program.

Source: Magid DJ, et al. Relationship between time of day, day of week, timeliness of reperfusion, and in-hospital mortality for patients with acute ST-segment elevation myocardial infarction. JAMA 2005;294:803-812.

No one can debate that reperfusion therapy with either percutaneous coronary intervention (PCI) or fibrinolysis reduces mortality for patients with ST-segment elevation myocardial infarction (STEMI). Additionally, it has been clearly proven that the shorter the time interval from symptom onset to treatment, the greater the benefit, regardless of which therapy is chosen. The purpose of this study was to determine the impact of time of day and day of week on the ability to meet American College of Cardiology/ American Heart Association guidelines for door-to-drug or door-to-balloon time expectations (≤ 30 and 90 minutes, respectively).1 A secondary goal of the study was to determine if identified time differences contributed to mortality.

This was a retrospective cohort study based on the National Registry of Myocardial Infarction (NRMI) database, which enrolled patients from 1999-2002. For this investigation, the authors examined 68,439 patients treated with fibrinolysis and 33,647 treated with PCI; patients were further divided into groups treated during regular hours (7 am-5 pm) or off-hours (5 pm-7 am on weekdays, and weekends). Door-to-drug and door-to-balloon times, as well as in-hospital mortality, were analyzed.

The findings (not surprisingly) demonstrated no significant differences in door-to-drug times between the two time periods (34.3 min off-hours vs 33.2 min regular hours, 95% CI 0.7-1.4, p <0.001), but marked differences in door-to-balloon times (116.1 min off-hours vs 94.8 min regular hours (95% CI 20.5-22.2, p < 0.001). When teased out, the longer door-to-ballon time during off-hours almost entirely was caused by longer decision-to-cardiac-cath-lab-arrival times. The delay in door-to-balloon time during off-hours resulted in significantly higher adjusted in-hospital mortality for patients who presented during these times (OR 1.07, 95% CI 1.01-1.14, p = 0.02). Predictably, two-thirds of the patients presented during off-hours, and one third presented during regular hours.


Do the terms off-hours and regular hours make anyone else bristle as much as they do me? I read these terms repeatedly in both the cardiology and (again, not surprisingly) the radiology literature. I know I am preaching to the converted, but patient care is a 24/7/365 proposition, and studies that show that I provide worse care at various times of the day or week that are completely out of my control drive me absolutely nuts. My chairman has a sage standard answer whenever we are presented with a new clinical pathway or patient care service in faculty meeting: it must work the same whether it is 1 pm on a normal weekday or 2 am on Christmas Eve. In general, those pathways/services that meet these criteria succeed, and those that don't fail.

A few important lessons can be taken from this large study. First, two-thirds of patients presenting with STEMI will come to the ED during the off-hours; therefore, whatever reperfusion strategy one pursues, this factor must be acknowledged. A facility that excels in door-to-balloon times during the 7 am-5 pm period but fails to approach the 90-minute mark during off-hours does a disservice to two-thirds of their STEMI patients.

Secondly, while we all acknowledge that time is muscle, this study outlines the potential in-hospital mortality consequence of this off-hour delay. If you come in during off-hours with a STEMI, your chance of surviving that hospitalization is diminished as compared with those patients who come in during regular hours.


1. Antman EM, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: Executive summary. J Am Coll Cardiol 2004;44:671-719.