Multilead Precordial ST-segment Monitoring

A QUARTER century has passed since the first reports describing use of precordial lead V5 to monitor for intraoperative ischemia were published, and over a decade has passed since we documented its sensitivity (75%) using continuous 12-lead monitoring in 100 patients. Since then, V5 has become “a clinical routine.” In this issue, Landesberg et al. present “the next generation,” monitoring a larger cohort (185 patients) undergoing higher-risk surgery (all vascular surgery), for a longer period of time (48–72 h). Their results extend our knowledge and add controversy, given their finding that leads V3 (75%) and V4 (83%) are either equal or more sensitive than V5 (75%). They recommend use of V4 over V5 since its ST-segment is most commonly isoelectric on the baseline electrocardiogram, extrapolating that this makes it more likely to reflect ischemic changes. They also recommend the use of two precordial leads to approach 95% sensitivity to detect ischemia or infarction. Should this study alter our current clinical practice? Should we “move to the right” in favor of V3 or V4 and abandon V5? Should we encourage bipartisanship by monitoring two precordial leads (requiring equipment modification)? Or should we take the Libertarian approach by encouraging simplicity in monitoring? I would argue that with the clinical data accumulated over the past 10–15 yr. documenting associations of perioperative tachycardia and ST-segment depression to adverse outcome and beneficial effects of -blockade, that sophisticated monitoring is considerably less important than adequate prophylaxis and therapy. However, since it is known that -blockade cannot ensure suppression of ischemia nor prevention of infarction in all patients, evaluation of the current status of multi-lead monitoring remains worthy of serious consideration. Reference cardiology texts state that subendocardial ischemia induced by demand-related stress is manifested by ST-segment depression in lead V5 and does not localize the anatomic site of coronary obstruction. Yet even Mason and Likar, the first to use the now universal torso-mounted axial leads during exercise treadmill testing (ETT), reported that V6, not V5, was the most sensitive lead! Subsequent investigators have reported varying sensitivity, particularly between V4, V5, and V6 9–13