Short- and long-term cause of death in patients undergoing isolated coronary artery bypass grafting: A nationwide cohort study

Objectives: Knowledge of the association between time and causes of death after coronary artery bypass grafting is sparse. We examined short- and long-term mortality and cause of death in patients undergoing coronary artery bypass grafting. Methods: With the use of Danish nationwide registries, we identified all patients undergoing isolated coronary artery bypass grafting from 1998 to 2014. Cause of death was classified as cardiovascular or noncardiovascular according to death certificates. Landmark analyses of the cumulative incidences of cardiovascular and noncardiovascular mortality after 1, 3, and 5 years after coronary artery bypass grafting were performed. Multivariable cause-specific Cox regression models were used to evaluate changes over time in the risk of all-cause, cardiovascular, and noncardiovascular mortality after 1 and 7 years after coronary artery bypass grafting, respectively. Results: Among 37,495 included patients, 12,230 (32.6%) died during a median follow-up of 7.4 years. Causes of death were classified as cardiovascular in 6459 patients (52.8%) and noncardiovascular in 5771 patients (47.2%). Within the first year, the incidence of cardiovascular death was higher compared with noncardiovascular death (3.9% vs 1.1%, P < .001). The cumulative incidences of cardiovascular and noncardiovascular were deaths similar in the periods 1 to 3 years (2.3% vs 2.6%, P = .004), 3 to 5 years (3.1% vs 3.2%, P = .75), and 5 to 7 years postsurgery (3.7% vs 4.0%, P = .07). The crude rates and adjusted risks of short- and long-term all-cause and cardiovascular mortality decreased during the study period despite an increase in age and burden of comorbidities. Conclusions: In patients undergoing coronary artery bypass grafting, cardiovascular causes were responsible for the majority of deaths within the first year. Deaths due to noncardiovascular causes gained importance over time elapsed since coronary artery bypass grafting.