MYOCARDIAL ISCHEMIA DURING NON-CARDIAC SURGICAL PROCEDURES IN PATIENTS WITH CORONARY-ARTERY DISEASE

The purpose of this study was to determine the incidence of ST-segment depression during anesthesia and operation. Graded exercise testing has demonstrated a high correlation between ST-segment depression and myocardial ischemia. Therefore, 11 patients without and 29 patients with known coronary-artery disease were monitored during surgical procedures with a commercially available exercise electrocardiographic monitor (Viagraph). Comparisons were made between this device, which monitored lead V5, and the standard operating room monitor, which monitored lead 11. Eleven of 29 patients in the disease group demonstrated significant ST depression. Nine of the 11 ischemic episodes were not recognized on the standard operating room monitor. Retrospective review of anesthetic records of those 11 patients with ST-segment depression revealed rate-pressure product values greater than 11,000 for ten of them. Postoperatively, three of the 11 patients with significant ST-segment depression had changing electrocardiograms compatible with ischemia. None of the control group demonstrated significant ST-segment depression. The incidence of ischemia was 38 per cent during anesthesia and operation in the coronary-artery-disease group. Lead V5 analysis is superior to lead 11 analysis in detecting ST-segment depression. The period in which intubation is performed is one of the highest-risk intervals during anesthesia and operation, particularly when it is associated with an increased rate-pressure product.