Abstract 2302: Preoperative Pulmonary Function Test Improves Risk Stratification and Predicts Postoperative Mortality in Patients Undergoing Cardiac Surgery
Chronic obstructive pulmonary disease (COPD) affects 4%–27% of patients undergoing cardiac surgery and confers a 3–5 fold increase in the risk of pulmonary complications and death. In clinical practice, COPD is often diagnosed on the basis of dyspnea and a history of smoking without performing a pulmonary function test (PFT). This practice leads to misdiagnosis in up to 20% of cases and such inappropriate classification of COPD alters the preoperative risk estimate in cardiac surgery patients, with potential impact on clinical decisions and surgical outcomes. Also, binary categorization of COPD (as present or absent) in the risk estimate models does not take into account the prognostic differences stemming from the severity of this disease. The objective of this project was to assess the relation of preoperative PFT parameters with postoperative outcomes in 1173 patients who underwent cardiac surgery at the Minneapolis Veterans Affairs Medical Center. Age was 67 ± 10 and 485 (41%) had a history of COPD. A total of 615 patients (52%) had normal Forced Expiratory Volume in 1 minute (FEV1 >80% of predicted), 343 (29%) had mild obstruction (FEV1 60%–79% of predicted) and 215 (18%) had moderate to severe obstruction (FEV1 < 60% of predicted). After PFT results, 217 patients (18%) were reclassified with regards to their COPD status, including 72 who carried a historical diagnosis of COPD but had a normal FEV1. There were a total of 41 operative deaths (3.5 %). In comparison to patients with normal FEV1, the odds of death was 1.6 fold higher (95% confidence interval (CI) 0.7 to 3.4, p=0.27) among those with mild COPD and 3.2 fold higher (95% CI 1.5 to 6.7, p=0.002) in those with moderate or severe COPD. In multivariate analysis, moderate or severe COPD was independently associated with death (odds ratio 2.2; 95% CI 1.00 – 4.8, p=0.05). Also, among the 854 patients who had Diffusing Capacity of the Lung for Carbon Monoxide (DLCO) testing, those with DLCO < 50% of predicted had a 5 fold increase in the odds of postoperative death (95% CI 2.3 to 10.9, p< 0.0001). In conclusion, these data show that PFT prior to cardiac surgery reclassifies the COPD status of a substantial number of patients and provides important prognostic information that the current risk estimate models do not include.