Dynamic QRS-complex and ST-segment monitoring by continuous vectorcardiography during carotid endarterectomy

Background. Many authors report a high incidence of cardiacevents during carotid endarterectomy. The aim of the presentstudy was to evaluate the usefulness of dynamic continuous on-linevectorcardiography for monitoring the occurrence of myocardialischaemia during carotid endarterectomy. Methods. We studied 21 patients undergoing carotid endarterectomy.Patients underwent general anaesthesia with isoflurane or sevoflurane.The vectorcardiogram was monitored continuously during carotidendarterectomy. Electrodes were placed according to the previouslydescribed lead system and connected to a computerized systemfor on-line vectorcardiography. Two trend variables were recorded:the QRS vector difference, which reflects changes in the shapeof the QRS complex; and the ST vector magnitude, which representsdeflection of the ST segment from the isoelectric level. TheST segment deflection was measured 60 ms after terminationof the QRS complex. Results. Vectorcardiography was successfully recorded in all21 patients. Three patients showed intraoperative vectorcardiogramabnormalities. In one of these three patients, both ST vectormagnitude and QRS vector difference increased after inductionof anaesthesia and ST vector magnitude returned to baselineafter administration of nitroglycerin. In the other two patients,both ST vector magnitude and QRS vector difference graduallyincreased after cross-clamping of the internal carotid arteryand ST vector magnitude returned to baseline after unclamping.QRS vector difference remained elevated for several hours inall three patients. Conclusions. Monitoring ST vector magnitude and QRS vector differenceby vectorcardiography may be useful for identifying myocardialischaemia during carotid endarterectomy. Br J Anaesth 2003; 90: 142–7