Relationship between time of day, day of the week and in-hospital mortality in patients undergoing emergency percutaneous coronary intervention.

Background: Previous studies have reported circadian variation in the rate of post-percutaneous coronary intervention (PCI) complications and mortality.
Aim: To assess whether in-hospital outcomes during the first 48h after admission are related to the time or the day when PCI is performed.
Methods: Emergency PCIs (2266 total; 1396 during regular hours and 870 during off hours) performed consecutively during a 3.5-year-period (2005-2008) were evaluated. The primary endpoint was death and the secondary endpoint was a composite score based on cardiovascular complications. The association between PCI start time and in-hospital outcome was assessed using multivariable logistic regression and propensity score analysis.
Results: The patients' mean age was 64.8 years and 77.3% were men. The highest death rate was for night-time PCI (3.6%), with a 5.1% occurrence rate for PCI performed between 00:00 and 03:59, and a 3.0% occurrence rate for weekend daytime PCI compared with 1.5% for weekday daytime (regular-hours) PCI. The frequency of occurrence of other clinical events did not vary significantly throughout the day. Compared with weekday daytime PCI, the odds ratio for mortality was 2.95 for night-time PCI (95% confidence interval [CI] 1.58-6.01; p=0.0007) and 2.42 for weekend daytime PCI (95% CI 0.97-6.01; p=0.06).
Conclusion: Our study shows a significant time-dependent effect on in-hospital deaths in patients treated with emergency PCI. Healthcare organization and circadian variation of ischaemic processes could explain this variation in mortality.