The effect of comorbid illness on mortality outcomes in cardiac surgery

Hypothesis: Comorbid conditions are associated with the risk of death from coronary artery bypass graft surgery. Design: Prospective cohort study data were collected on patient and disease characteristics and comorbid conditions including hypertension, diabetes, obesity, vascular disease, chronic obstructive pulmonary disease, cancer (excluding nonmelanoma skin cancer), dialysis-dependent renal failure, liver disease, and dementia. Statistical analysis used logistic regression for the calculation of adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Setting: Regional cardiac surgery database. Patients: A total of 27239 consecutive patients undergoing isolated coronary artery bypass graft surgery. Main Outcome Measure: In-hospital mortality rate. Results: The prevalence of comorbid conditions was as follows: hypertension, 64.3%; diabetes, 30.1%; obesity, 24.6%; severe obesity, 7.2%; vascular disease, 18.3%; chronic obstructive pulmonary disease, 10-9%; peptic ulcer, 7.5%; cancer, 3.8%; renal failure, 1.5%; liver disease, 0.6%; and dementia, 0.1%. After adjustment for patient and disease characteristics, including age, sex, previous cardiac surgery, priority of surgery, degree of left main coronary stenosis, number of diseased coronary arteries, and left ventricular ejection fraction, the following comorbid conditions were significant predictors of in-hospital mortality: diabetes (OR, 1.19; 95% CI 1.01-1.40; P=.03), vascular disease (OR, 1.67; 95% CI, 1.41-1.97; P<001), chronic obstructive pulmonary disease (OR, 1.57; 95% CI, 1.29-1.91; P<001), peptic ulcer (OR, 1.34; 95% CI, 1.05-1.71; P=.02), and dialysis-dependent renal failure (OR, 3.68; 95% CI, 2.65-5.13; P<001). There was no significant association between in-hospital mortality and hypertension, obesity or severe obesity, cancer, liver disease, or dementia. Conclusion: Even after adjustment for other patient and disease characteristics, comorbid conditions (especially diabetes, vascular disease, chronic obstructive pulmonary disease, peptic ulcer disease, and dialysis-dependent renal failure) are associated with significantly increased risk of death after coronary artery bypass graft surgery.