Predicting Risks for Cardiac Complications of Surgery

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The summary below is from the full report titled "Prospective Evaluation of Cardiac Risk Indices for Patients Undergoing Noncardiac Surgery." It is in the 5 September 2000 issue of Annals of Internal Medicine (volume 133, pages 356-359). The authors are K Gilbert, BJ Larocque, and LT Patrick.

What is the problem and what is known about it so far?

Predicting a patient's risk for cardiac complications during or shortly after surgery is important in getting patients ready for surgery. A person's risk for cardiac complications of surgery can be measured in several different ways. Each of these measures creates an overall risk index by assigning risk "points" for various findings in the patient's history, physical examination, and laboratory tests. In general, the more "points" that are assigned, the more likely the patient is to develop cardiac complications, such as heart attack, stroke, heart failure, or death. Little is known, however, about how well these measures work compared with one another.

Why did the researchers do this particular study?

To compare four existing methods of predicting patients' risks for complications during or shortly after surgery.

Who was studied?

The study included 2035 patients referred for medical consultation before undergoing a surgical procedure at two teaching hospitals in Ontario, Canada. The study did not include patients who were having heart surgery.

How was the study done?

Before surgery, the researchers estimated each patient's risk for cardiac complications using each of four indices: the American Society of Anesthesiology index, the Goldman index, the Detsky index, and the Canadian Cardiovascular Society index. They then followed patients to see who developed cardiac complications. This permitted them to compare the ability of the four indices to predict who would have a complication.

What did the researchers find?

Of the 2035 patients in the study, 130 had a cardiac complication (36 heart attacks, 67 episodes of heart failure, 27 episodes of angina, and 48 deaths). Patients with multiple complications were counted only once overall. Although all of the indices had some ability to predict cardiac complications, none of them were excellent at doing so, and no index was significantly better at predicting than the others.

What were the limitations of the study?

The study included patients at only two hospitals and only patients who were referred for a medical consultation. It is possible that the rate of complications in patients who did not get consultations differs from that seen in the study patients.

What are the implications of the study?

Although the four indices studied are somewhat helpful in predicting which patients will have a cardiac complication with surgery, none performed excellently and no one index was better than the others. There is room for improvement in the methods doctors use to predict patients' risks for developing cardiac complications after surgery.