Variation of mortality after coronary artery bypass surgery in relation to hour, day and month of the procedure

We studied 4,714 consecutive patients who underwent CABG at the Minneapolis Veterans Administration (VA) Medical Center between 1987 and 2009. We compared postoperative (30-day) mortality rates in relation to hour and day in which the operation was performed.Operations performed on weekends and after 4 PM had higher risk patients (p < 0.0001) and were more likely to be emergent (p < 0.0001), require intra-aortic balloon pump support (p < 0.0001) and result in postoperative complications (p < 0.0001) compared to those at regular work hours. Mortality was significantly higher when CABG was performed on weekends compared to weekdays (9.4% versus 2.5%; odds ratio (OR) 4.1, 95% confidence interval (CI) 1.6 to 10.4, p = 0.003), and after 4 PM compared to between 7 AM-4 PM (6.2% versus 2.2%; OR 2.9, 95% CI 1 to 8, p = 0.049). In multivariable analysis, when adjusted for the urgency of the operation and the VA estimated mortality risk score, these associations were no longer statistically significant.Mortality after CABG is higher when surgery is performed on the weekends and after 4 PM. These variations in mortality were related to higher patient risk, and urgency of the operation rather than external factors.Coronary artery bypass graft (CABG) surgery and percutaneous coronary interventions (PCI) are performed at off-hours when the circumstances dictate to do so. It has been known that primary PCI, for acute myocardial infarction, have higher mortality and worse outcomes when performed in the evening hours or at night in comparison to day time [1-6]. This is thought to be secondary to challenging patient factors, such as hemodynamic instability, myocardial loss and more difficult lesion characteristics and inferior processes of care, such as longer door-to-balloon times, less supervision, operator fatigue and limited resources [1,2]. Thus, the results of PCI are less optimal in patients who present after regular work hours [1,2].Published literature on the outcomes of sur