Risk Stratification Scores for Predicting Mortality in Coronary Artery Bypass Surgery

Introduction

Risk-stratification scores (RSSs) for heart surgery were introduced to estimate the perioperative risk of death during a heart operation or in the postoperative course, and to assess the postoperative risk of complication during the 30-day hospital stay [1] [2]. Available RSSs are based on different patient data and calculate the predicted risk with different algorithms (see below). Most of them were designed for patients undergoing surgery for coronary artery bypass grafting (CABG). Many RSSs are presently in clinical use for different purposes [3]. For quality management in CABG surgery, widespread use of a single RSS would be desirable, as this is a prerequisite for inter-institutional comparison [3] [4].

Therefore, we applied four RSSs - the Cleveland Clinic or Higgins Score (CCS/Higgins) [5], the Euro Score (Euro) [6], the French Score (French) [7] and the Parsonnet Score (Parsonnet) [8] - to patients in our institute who consecutively underwent CABG. The RSSs were tested for validity and practicability. The aim of our study was to determine the RSS most appropriate in clinical practice for the following: Firstly, predicting grouped risk for death; secondly, predicting individual risk for death; and thirdly, expressing the severity of patients' disease when they present for surgery.

References

• 1 Weightman W, Gibbs N, Sheminant M, Thackray N, Newman M. Risk predictors in coronary artery surgery: a comparison of four risk scores.  Med J Aust. 1997;  166 408-411
• 2 Immer F, Habicht J, Nessensohn K. et al . Prospective evaluation of 3 risk stratification scores in cardiac surgery.  Thorac Cardiovasc Surg. 2000;  48 134-139
• 3 Baretti R, Knecht J, Baumann-Baretti B. et al . Risk scores currently used in german heart surgery.  Thorac Cardiovasc Surg. 2001;  49 1-2
• 4 Osswald B, Tochtermann U, Schweiger P. et al . Target, application, and interpretation of scores and alternative methods for risk assessment in cardiac surgery.  Thorac Cardiovasc Surg. 2000;  48 72-78
• 5 Higgins T, Estafanous F, Loop F, Beck G, Blum J, Paranandi L. Stratification of morbidity and mortality outcome by preoperative risk factors in coronary artery bypass patients: a clinical severity score.  JAMA. 1992;  267 2344-2348
• 6 Nashef S, Roques F, Michel P. European system for cardiac operative risk evaluation (EuroSCORE).  Eur J Cardiothorac Surg. 1999;  16 9-13
• 7 Roques F, Gabrielle F, Michel P. Quality of care in adult heart surgery: proposal for a self-assessment approach based on a French multicenter study.  Eur J Cardiothorac Surg. 1995;  9 433-440
• 8 Parsonnet V, Dean D, Bernstein A. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease.  Circulation. 1989;  79 (suppl. 1) l-3-l-12
• 9 Hanley J, McNeil B. The meaning and use of the area under the receiver operating characteristic (ROC) curve.  Radiology. 1982;  143 29-36
• 10 Hanley J. Receiver operating characteristics (ROC) methodology: the state of the art.  Crit Rev Diagnostic Imaging. 1989;  29 307-335
• 11 Gabrielle F, Roques F, Michel P. et al . Is the Parsonnet's score a good predictive score of mortality in adult cardiac surgery: assessment by a French multicentre study.  Eur J Cardiothorac Surg. 1997;  11 406-414
• 12 Pinna-Pintor P, Bobio M, Sandrelli L. Risk stratification for open heart operations: comparison of centers regardless of the influence of the surgical team.  Ann Thorac Surg. 1997;  64 410-413