The relationship between predicted and actual cardiac surgical mortality: impact of risk grouping and individual surgeons.

OBJECTIVE: To study the relationship between predicted and actual mortality in a cardiac surgical practice and to determine whether there is a consistent relationship across risk groups and surgeons. METHODS: Risk information (Parsonnet score) was prospectively collected for 6213 consecutive adult patients undergoing cardiac surgery at one institution. The relationship between predicted mortality and actual mortality was analysed by risk group for all patients and for individual surgeons' practices. RESULTS: Predicted mortality was 10.2%. Actual mortality was 4.2%, giving a mortality ratio of 41% of predicted. This ratio was not consistent across the five major risk groups, ranging from 32% in moderate risk to 67% in very low risk patients. When analysed by individual surgical practices, the results were even more disparate, with a mortality index range between 0% for one surgeon's low risk patients to 150% for another surgeon's very low risk patients. CONCLUSION: The relationship between predicted and actual mortality at one institution may vary across the risk spectrum and between surgeons. This should be taken into account in preoperative risk assessment and informed patient consent. Individual surgeons may have strengths and weaknesses which are related to preoperative risk stratification.