Patients with acute myocardial infarction who arrive at a hospital during off-hours or on the weekend have longer times to restoration of normal blood flow and a higher risk of death than patients admitted during regular weekday hours, according to an article in the August 17 issue of the Journal of the American Medical Association.

Reperfusion therapy with either fibrinolytic therapy or percutaneous coronary intervention reduces risk of death for eligible patients with ST-segment elevation myocardial infarction. The shorter the time from symptom onset to treatment, the greater the survival benefit with either therapy.

David J. Magid, MD, MPH, and his American colleagues examined the relationship between time of day and day of week and reperfusion treatment times for ST-elevation myocardial infarction patients treated with fibrinolytic therapy or percutaneous interventions.

The authors hypothesized that understanding the reasons for variation in reperfusion treatment times by patient arrival period, and whether such variation is common to all hospitals and to both fibrinolytic therapy and percutaneous intervention, could inform design and targeting of interventions to improve timely reperfusion.

The study included 68,439 patients treated with fibrinolytic therapy and 33,647 treated with percutaneous intervention from 1999 through 2002. The researchers classified patient hospital arrival period into regular hours (weekdays, 7 a.m.-5 p.m.) and off-hours (weekdays 5 p.m.-7 a.m. and weekends).

The researchers found that most fibrinolytic therapy (67.9 percent) and percutaneous intervention patients (54.2 percent) were treated during off-hours. Door-to-drug times were slightly longer during off-hours (34.3 minutes) than regular hours (33.2 minutes; difference, 1.0 minute). In contrast, door-to-balloon times were substantially longer during off-hours (116.1 minutes) than regular hours (94.8 minutes; difference, 21.3 minutes).

A lower percentage of patients met guideline recommended times for door-to-balloon during off-hours (26 percent) than regular hours (47 percent). Door-to-balloon times exceeding 120 minutes occurred much more commonly during off-hours (42 percent) than regular hours (28 percent). Longer off-hours door-to-balloon times were primarily due to longer intervals between obtaining the electrocardiogram and patient arrival at the catheterization laboratory (off-hours 69.8 minutes vs. regular hours 49.1 minutes). This pattern was consistent across all hospital subgroups examined.

Patients arriving during off-hours had significantly higher adjusted in-hospital death rates than patients arriving during regular hours. This mortality difference was reduced by 43 percent when researchers adjusted for differences in reperfusion treatment times, suggesting that the higher off-hours mortality was due in part to longer reperfusion treatment times.

The researchers add that this study demonstrates that delays to percutaneous intervention during off-hours are common to all types of hospitals, including high-volume centers.

“Our study has implications for the delivery of reperfusion therapy during off-hours. Because delays to percutaneous coronary intervention (PCI) can result in lower survival rates for ST-elevation myocardial infarction patients, institutions providing PCI during off-hours should commit to doing so in a timely manner. One way to improve the timeliness of PCI during off-hours would be to provide onsite staffing of the cardiac catheterization laboratory around-the-clock. However, the clinical benefits of providing continuous in-house staffing of the cardiac catheterization laboratory must be weighed against the extra cost of providing such coverage,” the researchers wrote.

“Another possible solution is to cross-train noncardiac catheterization laboratory staff to assist with PCI during off-hours. However, the benefits of cross-training staff may not be realized unless rapid access to interventional cardiologists is also available. Still another approach would be to regionalize interventional cardiac care, transporting off-hour patients to institutions with continuous cardiac catheterization laboratory staffing and rapid door-to-balloon times. However, this approach would only affect patients transported by emergency medical services and the faster door-to-balloon times at regional centers might be offset by prolonged transport times to these hospitals,” the authors concluded.