Impact of patients' arrival time on the care and in-hospital mortality in patients with non-ST-elevation myocardial infarction.

Only a few studies have focused on the clinical characteristics and outcomes of non-ST-segment myocardial infarction (NSTEMI) during off-hours. The purpose of this study was to compare the impact of patients' arrival time on the care of NSTEMI and whether this pattern might affect hospital mortality. This study analyzed 4,736 NSTEMI patients included in the Korea Acute Myocardial Infarction Registry from November 2005 to January 2008. Patients' arrival time was classified into regular hours (weekdays, 9:00 a.m. to 6:00 p.m.) and off-hours (weekdays 18:01 p.m. to 8:59 a.m., weekends, and holidays). A subtotal of 2,225 (46.9%) patients was admitted during off hours, compared with 2,511 (53.1%) patients with regular-hour admission. A higher proportion of patients admitted during off-hours had a higher Killip class, had more frequent cardiopulmonary resuscitation, were less likely to receive percutaneous coronary intervention (PCI) (67.7% vs 72.7%, p <0.001), and had longer door-to-balloon times (28 hours, interquartile range: 11 to 63 vs 23 hours, interquartile range 4 to 67, p <0.001). Although unadjusted hospital mortality was associated with admission during off-hours (4.5% vs 3.3%, p = 0.023), after adjusting for all patients covariates, the difference in mortality was attenuated and was no longer statistically significant (odds ratio 0.94, 95% confidence interval 0.59 to 1.48, p = 0.793). In conclusion, despite receiving fewer PCIs and having substantially longer waiting times to PCI, patients admitted during off-hours may not be at risk for increased in-hospital mortality. If patients are treated within an appropriate reperfusion strategy according to their clinical risk, arrival time may not influence on mortality.