title: Right ventricular outflow tract pacing causes intraventricular dyssynchrony in patients with sick sinus syndrome: a real-time three-dimensional echocardiographic study.
abstract: BACKGROUND
  The optimal right ventricular pacing site remains controversial. The aim of this study was to assess how acute right ventricular outflow tract (RVOT) pacing affects global left ventricular function and intraventricular dyssynchrony of the left ventricle.
  
  
  METHODS
  Thirty-six patients with sick sinus syndrome and intact intrinsic atrioventricular conduction were enrolled. All patients underwent dual-chamber permanent pacemaker implantation, with the atrial lead placed in the right atrial appendage and the right ventricle lead positioned at the septal site of the RVOT. Chamber size, dyssynchrony index, myocardial performance index, and global left ventricular ejection fraction were determined using transthoracic two-dimensional echocardiography, tissue Doppler echocardiography, and real-time three-dimensional echocardiography.
  
  
  RESULTS
  RVOT pacing increased the myocardial performance index (0.42 +/- 0.21 with RVOT pacing vs 0.35 +/- 0.21 without RVOT pacing, P = .002) and decreased the global left ventricular ejection fraction on real-time 3-dimensional echocardiography (51.4 +/- 6.2% with RVOT pacing vs 55.9 +/- 7.1% without RVOT pacing, P = .001). Intraventricular dyssynchrony of the left ventricle induced by RVOT pacing was determined by increased septal-to-posterior wall motion delay (69.7 +/- 54.0 ms with RVOT pacing vs 22.8 +/- 22.3 ms without RVOT pacing, P < .0001), increased systolic and diastolic dyssynchrony by tissue Doppler echocardiography, and increased systolic dyssynchrony index when assessed using real-time three-dimensional echocardiography (5.56 +/- 1.74% with RVOT pacing vs 4.05 +/- 1.61% without RVOT pacing, P < .0001).
  
  
  CONCLUSIONS
  Acute RVOT pacing adversely affects left ventricular function and increases intraventricular dyssynchrony in patients with sick sinus syndrome.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Taiwan, China.
authors.forename: Wen-Hao
authors.initials: WH
authors.lastname: Liu
authors.forename: Bih-Fang
authors.initials: BF
authors.lastname: Guo
authors.forename: Yung-Lung
authors.initials: YL
authors.lastname: Chen
authors.forename: Tzu-Hsien
authors.initials: TH
authors.lastname: Tsai
authors.forename: Morgan
authors.initials: M
authors.lastname: Fu
authors.forename: Sarah
authors.initials: S
authors.lastname: Chua
authors.forename: Mien-Cheng
authors.initials: MC
authors.lastname: Chen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000209:etiology; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012804:Sick Sinus Syndrome / Q000628:therapy*; D018487:Ventricular Dysfunction, Left / Q000209:etiology*