An electrocardiographic lead system for coronary artery bypass surgery

To identify the optimal subset of two electrocardiographic (ECG) leads for monitoring of ischemic ST depression and elevation during coronary artery bypass grafting (CABG) surgery.

Prospective observational clinical study.

University hospital cardiac surgery operating room.

120 patients undergoing primary surgery or reoperation for CABG.

All six ECG limb leads and a precordial matrix of four leads were recorded intraoperatively approximately every 3 minutes. The limb leads were placed on the torso in modified Mason-Likar positions. The precordial leads were placed at V4, V5, and one interspace below them.

New ischemic 1 mm ST depression and elevation episodes were determined. New ST deviation episodes attributed to nonischemic causes such as cooling at the onset of cardiopulmonary bypass (CPB), defibrillation at the end of CPB, new cardiac conduction changes after CPB, and postoperative pericarditis were excluded. Fixed ST deviation that did not change by 1 mm in the perioperative period was also excluded. Leads V5 and III constituted the best two-lead set. These leads recorded 15 of the 16 ischemic ST elevation episodes and all 8 ischemic ST depression episodes. One ST elevation episode was not recorded intraoperatively but was recorded in lead V1 in the immediate postoperative ECG. Leads V5 and II recorded 13 of the 16 ischemic ST elevation episodes and all 8 ischemic ST depression episodes. Lead V5 alone missed 8 episodes of ischemic ST elevation and one episode of ischemic ST depression.

For monitoring of ischemia during CABG, leads V5 and III are preferable to other two-lead sets, including the commonly used V5 and II. No single lead is adequate. Lead V5 alone missed approximately one half the episodes of ST elevation that were recorded by lead III or another inferior lead.