Cardiovascular morbidity and mortality display a distinct time dependence also known as circadian variation. Whether such time dependence extends to the risk of procedural-related mortality after percutaneous coronary intervention (PCI) is presently unknown.

Inhospital mortality was analyzed in 6347 patients with PCI start times from 8:00 am to 6:59 pm (“usual” workday). The sample was divided into 3 evenly populated groups (morning start 8:00-10:59 am, midday start 11:00 am-1:59 pm, afternoon start 2:00-6:59 pm). The association between procedural start time and mortality was assessed using multivariable analysis including a propensity score accounting for factors associated with procedural start time.

There was a significant, nonlinear relationship between procedural-related mortality and start time (P = .03). Afternoon start patients were at higher adjusted risk of mortality compared with midday start patients (OR 2.03, 95% CI 1.07-3.83, P = .03 ). Morning start patients were also at higher risk compared with midday start patients although the association was not statistically significant (OR 1.73, 95% CI 0.89-3.39, P = .11).

There is a significant time-dependent variation in the risk of inhospital PCI-related mortality during usual working hours. The highest risk period, taking into account numerous factors that confound this association, is the latter part of the workday. A second period of apparent greater risk occurs during the early part of the workday and is consistent with our present understanding of circadian variation in cardiovascular disease processes.