Age-dependent trends in postoperative mortality and preoperative comorbidity in isolated coronary artery bypass surgery: a nationwide study

OBJECTIVES: An increasing number of octogenarians are being subjected to coronary artery bypass grafting (CABG). The purpose of this study was to examine age-dependent trends in postoperative mortality and preoperative comorbidity over time following CABG. METHODS: All patients who underwent isolated CABG surgery between January 1996 and December 2012 in Denmark were included. Patients were identified through nationwide administrative registers. Age was categorized into five different groups and time into three periods to see if mortality and preoperative comorbidity had changed over time. Predictors of 30-day mortality were analysed in a multivariable Cox proportional-hazard models and survival at 1 and 5 years was estimated by Kaplan-Meier curves. RESULTS: A total of 38 830 patients were included; the median age was 65.4 ± 9.5 years, increasing over time to 66.6 ± 9.5 years. Males comprised 80%. The number of octogenarians was 1488 (4%). The median survival was 14.7 years (60-69 years), 10.7 years (70-74 years), 8.9 years (75-79 years) and 7.2 years (≥80 years). The 30-day mortality rate was 3%, increasing with age (1% in patients 80 years), respectively. The proportion of patients >75 years increased from 10 to 20% during the study period as well as the proportion of patients undergoing urgent or emergency surgery. The burden of comorbidities increased over time, e.g. congestive heart failure 13-17%, diabetes 12-21%, stroke 9-11%, in all age groups. Age and emergency surgery were the main predictors of 30-day mortality: age >80 years hazard ratio (HR): 5.75, 95% confidence interval (CI): 4.41-7.50, emergency surgery (HR: 5.23, 95% CI: 4.38-6.25). CONCLUSION: Patients are getting older at the time of surgery and have a heavier burden of comorbidities than before. The proportion of patients undergoing urgent or emergency surgery increased with age and over time. Despite this, the 30-day mortality decreased over time and long-term survival increased, except in octogenarians where it was stable. Octogenarians had substantially higher 30-day mortality compared with younger patients but surgery can be performed with acceptable risks and good long-term outcomes.