title: Separated right and left ventricular excitation during right ventricular septal pacing in a patient with narrow QRS wave: a case report.
abstract: BACKGROUND
  Right ventricular septal pacing is thought to be better than right ventricular apical pacing for shortening the QRS duration and for preserving left ventricular function. However, right ventricular septal pacing may not be effective in all cases. In this case report, we present a rare case in which right ventricular septal pacing induced thoroughly separated right and left ventricular excitation despite the presence of a relatively narrow QRS wave during atrium-only pacing.
  
  
  METHODS
  We report a case of 63-year-old Japanese man with cardiomyopathy with an implantable cardioverter defibrillator placement for ventricular tachycardia. Three years after implantation, he developed second-degree atrio-ventricular block. Therefore, atrio-ventricular sequential pacing was started; then his heart failure was much worsened. His electrocardiogram showed a dissociated biphasic QRS wave during right ventricular high-septal pacing, despite the presence of a non-fragmented QRS morphology during atrium-only pacing. An activation map during right ventricular high-septal pacing showed that right ventricular conduction started at the pacing site and ended at the right ventricular basal inferior site. Subsequently after a 10 ms interval, left ventricular conduction started at the left ventricular posteroseptum and ended at the left ventricular lateral wall. These data indicate that during right ventricular high-septal pacing, the first component of the QRS wave supposedly reflects only right ventricular excitation and the second component only left ventricular excitation. Also due to the intracardiac electrograms, it was assumed that this phenomenon was caused by transversely limited severe transseptal conduction disturbance.
  
  
  CONCLUSIONS
  It should be noted that even ventricular septal pacing could evoke harmful interventricular dyssynchrony due to transversely limited severe septal conduction disturbance, despite the presence of a relatively narrow QRS wave.
authors.forename: Takanori
authors.initials: T
authors.lastname: Yaegashi
authors.affiliation: Department of Cardiology, Kanazawa University Hospital, 13-1, Takara-machi, Kanazawa 920-8641, Japan. hfurusho@m-kanazawa.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Furusho
authors.forename: Akio
authors.initials: A
authors.lastname: Chikata
authors.forename: Soichiro
authors.initials: S
authors.lastname: Usui
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kaneko
authors.forename: Masakazu
authors.initials: M
authors.lastname: Yamagishi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takamura
mesh_terms: D001145:Arrhythmias, Cardiac / Q000150:complications; D054537:Atrioventricular Block / Q000150:complications / Q000628:therapy*; D053840:Brugada Syndrome; D000075224:Cardiac Conduction System Disease; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D009202:Cardiomyopathies / Q000150:complications; D017147:Defibrillators, Implantable; D006329:Heart Conduction System / Q000002:abnormalities; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000150:complications; D018754:Ventricular Dysfunction / Q000209:etiology*; D054088:Ventricular Septum