Risk stratification in heart surgery: comparison of six score systems

Objective: Risk scores have become an important tool in patient assessment, as age, severity of heart disease, and comorbidity in patients undergoing heart surgery have considerably increased. Various risk scores have been de veloped to predict mortality after heart surgery. However, there are signif icant differences between scores with regard to score design and the initia l patient population on which score development was based. It was the purpo se of our study to compare six commonly used risk scores with regard to the ir validity in our patient population. Methods: Between September 1, 1998 a nd February 28, 1999, all adult patients undergoing heart surgery with card iopulmonary bypass in our institution were preoperatively scored using the initial Parsonnet, Cleveland Clinic, French, Euro, Pens, and Ontario Provin ce Risk (OPR) scores. Postoperatively, we registered 30-day mortality, use of mechanical assist devices, renal failure requiring hemodialysis or hemof iltration, stroke, myocardial infarction, and duration of ventilation and i ntensive care stay. Score validity was assessed by calculating the area und er the ROC curve. Odds ratios were calculated to investigate the predictive relevance of risk factors. Results: Follow-up was able to be completed in 504 prospectively scored patients. Receiver operating characteristics (ROC) curve analysis for mortality showed the best predictive value for the Euro score. Predictive values for morbidity were considerably lower than predic tive values for mortality in all of the investigated score systems. For mos t risk factors, odds ratios for mortality were substantially different from ratios for morbidity. Conclusions: Among the investigated scores, the Euro score yielded the highest predictive value in our patient population. For most risk factors, predictive values for morbidity were substantially diffe rent from predictive values for mortality. Therefore, development of specif ic morbidity risk scores may improve prediction of outcome and hospital cos t. Due to the heterogeneity of morbidity events, future score systems may h ave to generate separate predictions for mortality and major morbidity even ts. (C) 2000 Elsevier Science B.V. All rights reserved.