Electrocardiographic characteristics in right ventricular vs biventricular pacing in patients with paced right bundle-branch block QRS pattern ☆ Marwan Refaat, MD, a Moussa Mansour, MD, b Jagmeet P. Singh, MD, PhD, b Jeremy Ruskin, MD, b E. Kevin Heist, MD, PhD b, ⁎ a Cardiac Electrophysiology Service, University of California San Francisco Medical Center, San Francisco, California, USA b Cardiac Arrhythmia Service, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA Received 15 January 2010 Abstract Background: A paced right bundle-branch block (RBBB) QRS morphology is present in most patients with biventricular pacing (BiVP) but is also present in some patients with right ventricular pacing (RVP). The aim of this study was to determine if there are electrocardiographic characteristics that distinguish BiVP from RVP in patients with a paced RBBB QRS pattern. Methods: Twelve-lead–paced electrocardiograms (ECGs) were analyzed from 356 consecutive patients (302 RVP and 54 BiVP). Further analyses were performed on those ECGs with a paced RBBB morphology, which included QRS pattern, axis, amplitude, and precordial transition. Chest radiography and coronary sinus venography were used to determine the location of the pacing leads. Results: Fifty (16.6%) of 302 RVP ECGs and 50 (92.6%) of 54 BiVP ECGs had RBBB-paced morphology, respectively. Electrocardiographic characteristics identified in this study with a paced RBBB QRS morphology that are associated with RVP but not with BiVP (P b .05) include positive concordance in the precordial leads, qR configuration in lead V 1 , and a late QRS transition beyond lead V 3 . Biventricular pacing had shorter mean–paced QRS duration than did RVP and was associated with right superior quadrant mean frontal QRS axis (P b .05). Right ventricular pacing was associated with a mean frontal QRS axis in the left superior quadrant (P b .05). Regarding left ventricular (LV) pacing site, a late precordial transition (especially beyond lead V 2 ) was significantly associated with a more posterior LV lead location (P b .05). Conclusions: Even among patients with a paced RBBB QRS pattern, the 12-lead ECG can help distinguish RVP from BiVP and determine LV lead location during BiVP. This information may be useful in evaluating nonresponse to BiVP resulting either from LV noncapture (with consequent RVP) or from suboptimal LV lead location during BiVP. © 2011 Elsevier Inc. All rights reserved. Keywords: Electrocardiography; Cardiac resynchronization therapy; Pacemaker Introduction Biventricular pacing (BiVP) is an established therapy for patients with systolic heart failure refractory to medical therapy and intraventricular conduction delay. 1-4 Patients typically undergo implantation of a cardiac resynchroniza- tion device along with 3 pacing leads, as follows: a standard right atrial lead, a standard right ventricular (RV) lead, and a specialized left ventricular (LV) lead, which is placed into a distal cardiac vein by way of the coronary sinus through a guiding catheter. The presence, diameter, angulation, and tortuosity of coronary veins as visualized by retrograde venography determine their acceptability for the placement of a lead in a predetermined location. 5,6 The paced 12-lead electrocardiogram (ECG) is a simple, inexpensive, and valuable tool in the assessment of patients with pacemakers. The data on ECG patterns in BiVP are still limited. There are relatively few publications that assessed 12-lead ECG characteristics comparing RV pacing (RVP) vs Available online at www.sciencedirect.com Journal of Electrocardiology 44 (2011) 289 – 295 www.jecgonline.com Abbreviations: ECG, electrocardiogram; LV, left ventricle; RV, right ventricle; BiV, biventricular; RBBB, right bundle-branch block; BiVP, biventricular pacing; RVP, right ventricular pacing. ☆ Presented as an abstract at the 58th Annual Scientific Sessions of the American College of Cardiology, March 30, 2009, Orlando, FLA. ⁎ Corresponding author. Cardiac Arrhythmia Service and Cardiac Unit, Massachusetts General Hospital, 55 Fruit Street, Gray 109, Boston, MA 02114, USA. E-mail address: kheist@partners.org 0022-0736/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jelectrocard.2010.08.003