Right Bundle Branch Block-Like Pattern During Ventricular Pacing: A Surface Electrocardiographic Mapping Technique to Locate the Ventricular Lead

Background: In patients with paced rhythm, a right bundle branch block (RBBB)-like pattern may suggest inadvertent left ventricular (LV) lead placement. However, in most cases, the lead is indeed in the right ventricle as intended. Methods: We performed a retrospective analysis of postimplantation electrocardiograms (ECGs) for the period 2000-2013 to determine the prevalence of a RBBB-like pattern. A 12-lead ECG was recorded in the standard position and with displacement of leads V-1-V-2 to the fifth and sixth intercostal spaces (ICSs), assessing the ability of this manoeuvre to unmask a concealed LBBB-like pattern. Patients with true LV pacing, both endocardial and epicardial, were used as controls (n = 10). Results: A total of 943 patients were analyzed. The prevalence of RBBB-like pattern was 8.1% (n = 77), and 26 patients were included in the study. Displacement of leads V1-V2 to the fifth ICS resulted in transition to a LBBB-like pattern with a QS wave in V-1 in 14 of 26 patients (sensitivity, 53%; specificity, 100%), whereas displacement to the sixth ICS resulted in a QS pattern in all patients (sensitivity and specificity, 100%). In all patients in the control group, the ECG depicted a RBBB configuration with leads V-1-V-2 in the standard position, as well as at the fifth and sixth ICSs. Conclusions: In patients with paced rhythm and a RBBB-like pattern on the 12-lead ECG, displacement of leads V-1-V-2 to the sixth ICS accurately identifies the presence of true right ventricular pacing.