Comparison of CB5 and V5 leads for intraoperative electrocardiographic monitoring.

Electrocardiogram lead CB5 was compared with lead V5 kin 27 patients undergoing coronary artery bypass graft surgery. Lead CB5 is a bipolar lead consisting of a negative electrode over the center of the right scapula and the positive electrode over the fifth interspace in the anterior axillary line. Comparison of CB5 and V5 tracings made while the chest was closed showed the ventricular deflections to be 20% larger in the CB5 lead. The ventricular deflections were highly correlated (r = 0.95 to 0.98). The average P wave voltage was 90% greater in the CB5 lead, and the relative increase in P wave voltage was greater (p less than 0.01) than the 20% increase in the RS deflection. Tracings made while the chest was open gave similar results. The CB5 lead is simple to apply and provides tracings equivalent to the V5 when monitoring for ischemia while allowing easier recognition of P waves.