Severe morbidity after coronary artery surgery: development and validationof a simple predictive clinical score

Aims To develop a predictive clinical risk score of postoperative morbidity after coronary artery bypass grafting. Methods and Results Data were collected retrospectively from 679 patients u ndergoing emergency or planned bypass surgery between 1 January and 31 Dece mber 1996. The incidence of morbidity was 23%. Multivariate stepwise logist ic regression analysis on two-thirds of the patients identified eight indep endent risk factors for severe morbidity. Six of these were;ere pre-operati ve: symptomatic right heart failure, previous ventricular arrhythmias, prev ious coronary bypass surgery, chronic pulmonary disease, ST changes on pre- operative electrocardiogram, body mass index 424 kg. m(-2), and two were in tra-operative factors: the surgeon who operated, and the cardiopulmonary by pass time. A predictive clinical risk score was developed with the six pre- operative risk factors. The negative predictive value of the model is 87% a nd the area under the receiver operating characteristic curve is 0.77. When tested on the remaining patients not used for developing the model, the ar ea under the curve is 0.5. Conclusion This pre-operative risk score provides a simple method of risk s tratification for patients undergoing coronary artery surgery. However, as for all predictive models, the performance of the score decreases when appl ied to a population other than that used to develop it.