Is Exercise Electrocardiography Useful for Risk Stratification before Noncardiac Surgery?Gauss et al.(page 38)

During a 2-yr period, Gauss et al.  examined 204 patients who had coronary artery disease or were at risk for it before their scheduled noncardiac surgeries. Patients underwent exercise stress testing on a supine bicycle ergometer 1 day before surgery. A 12-lead electrocardiogram was recorded at rest, once per minute during exercise and during recovery until the electrocardiogram reverted to preexercise morphology. The exercise electrocardiogram was classified as abnormal if new horizontal or down-sloping ST-segment depressions of more than 0.1 mV were seen in three consecutive beats without baseline variation. Rest and exercise electrocardiograms were evaluated by two independent investigators blinded to patient identity and clinical outcome. A third investigator was consulted if the first two interpretations differed.

Echocardiography was performed on each patient before surgery. Patients were monitored with a two-channel Holter electrocardiographic recorder from the evening before surgery until the morning of the second postoperative day. Twelve-lead electrocardiograms and creatine kinase, creatinine kinase MB, and troponin-T measurements were assessed until the sixth postoperative day. One of the study authors also performed a history and physical examination of each patient until the fifth postoperative day and on the day of discharge from the hospital. Telephone interviews with patients were conducted 30 days after surgery to obtain cardiac histories.

Perioperative cardiac events (6 myocardial infarctions, 10 cases of minor myocardial cell injury) were observed in 16 of the 185 patients available for final examination. Despite the small sample size and the fact that physicians treating the patients were not blinded to preoperative resting and exercise electrocardiographic findings, the study showed that an ST-segment depression of 0.1 mV or more was an independent predictor of perioperative cardiac complications. An abnormal resting electrocardiogram was not an independent predictor of such complications. A combination of a clinical parameters, such as definite coronary artery disease and the type of surgery, with the results of the electrocardiographic exercise stress test, allowed sufficient risk stratification.