title: RV-only pacing can produce a Q wave in lead 1 and an R wave in V1: implications for biventricular pacing.
abstract: BACKGROUND
  Biventricular (bi-v) pacing improves congestive heart failure and mortality in patients with left ventricular (LV) dysfunction and electrical dyssynchrony. Effective resynchronization must include an LV pacing contribution to the QRS. Leads 1 and V1 are often exclusively used to verify proper biventricular pacing.
  
  
  METHODS
  In 40 patients referred to our cardiac resynchronization therapy (CRT) optimization clinic, 12-lead electrocardiograms (ECGs) were obtained during bi-v pacing, right ventricular (RV)-only pacing, LV-only pacing, and a range of atrio-ventricular and ventriculo-ventricular intervals. The presenting bi-v QRS morphology was compared to RV and LV pacing, and RV-only pacing was evaluated for the presence of a Q wave in lead 1 and an R wave in V1.
  
  
  RESULTS
  In 22 patients (55%), RV pacing produced an initial Q wave in lead 1 and/or R wave in V1, mimicking bi-v pacing. In three patients, the presenting bi-v paced ECG looked identical to RV-only pacing. In 28 patients (70%), LV pacing was advanced by a mean of 30 ms after CRT optimization. Using all 12 ECG leads, especially the precordial leads, was necessary to appreciate the QRS changes that occurred when LV pacing meaningfully contributed to electrical activation.
  
  
  CONCLUSIONS
  Because of LV pacing latency, some patients require an earlier LV offset to achieve proper resynchronization pacing. Commonly used ECG criteria cannot verify meaningful LV pacing contribution during biventricular pacing because RV-only pacing often creates a Q wave in lead 1 and/or R wave in V1. The full 12-lead ECG during biventricular pacing should be compared with isolated RV and LV pacing to verify that LV pacing is properly contributing to the QRS.
authors.affiliation: Electrophysiology Section, Division of Cardiology, Temple University Health System, Philadelphia, Pennsylvania.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Cooper
authors.forename: Rutuke K
authors.initials: RK
authors.lastname: Patel
authors.forename: Anthony
authors.initials: A
authors.lastname: Emmi
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: James N
authors.initials: JN
authors.lastname: Kirkpatrick
mesh_terms: D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D006352:Heart Ventricles; D006801:Humans; D018579:Patient Selection; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control*; D014693:Ventricular Fibrillation / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control*
keywords: 12-lead electrocardiogram; QRS morphology; biventricular optimization; cardiac resynchronization therapy; electrocardiography; right ventricular pacing