ST-elevation myocardial infarction mortality in a major academic center "on-" versus "off-" hours

A higher mortality rate for weekend myocardial infarction (MI) admissions has been reported and attributed to the lower availability of primary percutaneous coronary intervention (PCI) during off-hours. However, the data are conflicting and, furthermore, inapplicable to hospitals where primary PCI is invariably performed.

This study was conducted in a tertiary hospital where primary PCI is routinely performed in all patients with ST-elevation myocardial infarction (STEMI). Patients admitted during on-hours (Monday through Friday 7 am-7 pm) where compared to off-hours patients (including weekends). The primary endpoint of in-hospital mortality, cardiogenic shock and recurrent MI was examined. A second analysis that excluded STEMI transfers, in-hospital mortality and reperfusion times was examined.

Between 2003 and 2007, 747 STEMI patients (46% on-hours vs. 56% off-hours) underwent primary PCI. Demographic characteristics were similar between on- and off-hours groups. However, off-hours STEMI admissions had significantly greater in-hospital mortality rates (8% vs. 3.7%; p = 0.01) and higher rates of cardiogenic shock (37% vs. 24%; p = 0.0001). Admission arrival time was an independent predictor of in-hospital mortality (hazard ratio [HR] 3.98, 95% confidence interval [CI] 1.10-14.38; p = 0.035). Longer door-to-balloon times (DTB) were observed during off-hours (134 vs. 109 minutes; p < 0.0001), even after excluding the transfer population (63 vs. 89 minutes; p < 0.0001).

Higher rates of in-hospital mortality and cardiogenic shock may be expected in STEMI patients admitted during off-hours, even when primary PCI is performed. Longer DTB times during off-hours may partially explain our findings. Strategies to optimize reperfusion time during off-hours, including perhaps a 24/7 in-house "STEMI team" may be necessary.