INCIDENCE AND ELECTROCARDIOGRAPHIC LOCALIZATION OF SAFE RIGHT BUNDLE-BRANCH BLOCK CONFIGURATIONS DURING PERMANENT VENTRICULAR PACING

The usual morphology for paced events originating from the right ventr icle has a left bundle branch block (BBB) pattern. However, in a few p atients, right BBB configurations are identified. It is important to d ifferentiate safe right BBB patterns from those caused by septal or fr ee wall perforation, Paced electrocardiograms were examined in 179 con secutive patients who underwent pacemaker placement, Fourteen patients (8%) were identified with right BBB configurations. Posteroanterior a nd lateral chest radiographs and echocardiograms were evaluated specif ically to identify the pacing lead location in this group, In addition , 152 paced episodes from published reports were combined with our pop ulation to create an electrocardiographic algorithm differentiating ri ght ventricular septum, right ventricular apex, coronary venous, and l eft ventricular pacing, Chest radiographs and echocardiographic lead l ocations correlated perfectly in the 11 patients available for echocar diograms. With use of a left superior axis and precordial transition b y lead V-3, right ventricular right BBB morphologies were correctly de tected in 18 of 21 patients (86% sensitivity, 99% specificity) and app ropriately separated from left ventricular pacing in 18 of 19 patients (95% positive predictive valve), Therefore, 12-lead electrocardiogram s are a rapid, reliable means of separating right and left ventricular right BBB pacing morphologies. Prudent use of these criteria will hel p eliminate unnecessary echocardiography, anticoagulation, and lead re vision.