Use of the right-sided precordial lead V4R in the detection of intraoperative myocardial ischemia.

This study evaluated the benefit of additional electrocardiographic monitoring of the right precordial lead V4R for detection of ST segment changes during elective coronary artery bypass surgery in 210 patients. ST segment analysis was performed for leads I, II, CB5, and V4R. ST segment changes were noted in 60 patients. Of these, 32 had combined left-sided and right-sided coronary artery disease (group A), and 28 had only left-sided coronary artery disease on coronary angiography (group B). Lead sensitivity was estimated assuming that all ST segment changes were true positive responses. Sensitivity using a single lead was greatest for lead CB5 in the two groups (76% in group A and 78% in group B). Sensitivity for lead I was low in both groups (34% in group A and 26% in group B). Sensitivity for lead II was 63% in group A and 52% in group B, and sensitivity for lead V4R was 71% in group A but only 37% in group B. Combination of leads V4R and CB5 increased sensitivity to 98% in group A. In group B, this lead combination had a sensitivity of 93%, but lead combinations I-CB5-V4R and II-CB5-V4R were more sensitive (97% and 100%, respectively). The monitoring of lead V4R allowed detection of 20% of ST segment changes in group A that would have passed undetected if only leads I, II, and CB5 were monitored. These results demonstrate the value of additional electrocardiographic monitoring of the right precordial lead V4R during coronary artery bypass grafting in patients with right-sided coronary artery disease.