A simple classification of the risk in cardiac surgery: the first decade

Abstract

Since 1980, the operative risk in all our cardiac surgical patients has been assessed before surgery. In light of reports of changes in cardiac surgical populations, we reexamined our practice and risk classification. The purpose of this study was to compare the surgery performed, the characteristics of the patients operated upon and the hospital mortality in our institution in two epochs ten years apart. In 1989-90, the 2029 consecutive cardiac surgical patients who had the same operations as the 500 patients of a 1980 study in our institution were prospectively stratified using our risk classification based on the number of risk factors (RFs) present: normal-risk patient = no RF, increased risk = 1 RF, high risk ≥ 2 RFs. These two cohorts of patients were compared. From 1980 to 1990, the proportion of high-risk patients tripled whereas the proportion of normalrisk patients diminished by one third and the proportion of increased risks remained unchanged. The incidence of the following RFs increased: poor left ventricular function, advanced age, emergency surgery, reoperation and other systemic disorders. In coronary artery surgery patients, the incidence of unstable angina/ recent myocardial infarction and of obesity also increased. In noncoronary artery surgery patients, the incidence of heart failure increased while obesity remained unchanged. The difference in hospital mortality among the three risk classes was significant within both study periods. The mortality in each risk class and total mortality did not change between 1980 and 1990. Complex surgery carried a higher mortality than simple surgery (8.7% vs 2.6% in 1980 and 11.7% vs 4.1% in 1990). A stable hospital mortality and an increase in the proportion of high-risk patients in the more recent population may be attributed to recently improved therapeutic measures. The risk classification that we use remains a practical, reliable and simple clinical tool to estimate outcome and quality of care. The required data are readily available at the preanaesthetic visit. Complex surgery is a new RF. © 1993 Canadian Anesthesiologists.