Impact of chronic obstructive pulmonary disease severity on surgical outcomes in patients undergoing non-emergent coronary artery bypass grafting

Although the association between chronic obstructive pulmonary disease (COPD) and adverse surgical outcomes has been previously demonstrated, the impact of COPD severity on postoperative mortality and morbidity remains unclear. Our objective was to analyse the prognostic implication of COPD stages as defined by the Global Initiative for Chronic Obstructive Lung Disease. Between September 1997 and April 2010, 13 638 patients undergoing first time isolated CABG were retrospectively reviewed, of whom 2421 patients were excluded due to lack of spirometry records or restrictive pattern on spirometry. The remaining 11 217 patients were divided into three groups: group 1 (including patients with normal spirometry and patients with mild COPD (FEV1/FVC ratio < 70%, FEV1 >= 80% predicted), group 2 (moderate COPD: FEV1/FVC ratio < 70%, 50% < FEV1 < 80% predicted) and group 3 (severe COPD: FEV1/FVC ratio < 70%, FEV1 < 50% predicted). Logistic regression was used to examine the effect of COPD severity on early mortality and morbidity, after adjusting for differences in patient characteristics. Early mortality in the three groups was 1.4, 2.9 and 5.7% respectively (P < 0.001). Similarly, a consistent trend of increasing frequency of postoperative complications with advanced COPD stage was noted. On multivariate analysis, severe COPD was found to be significantly associated with early mortality [adjusted OR, 2.31 (95% CI) (1.23-4.36)], P = 0.01. The severity of COPD as defined by spirometry can be a prognostic marker in patients undergoing CABG. Spirometric criteria may help refining currently used operative risk scores.