title: Difference in prevalence and pattern of mechanical dyssynchrony in left bundle branch block occurring in right ventricular apical pacing versus systolic heart failure.
abstract: BACKGROUND
  This study compared the prevalence and pattern of mechanical dyssynchrony in patients with normal heart and right ventricular apical (RVA) pacing versus patients with systolic heart failure (SHF) and spontaneous left bundle branch block (LBBB).
  
  
  METHODS
  A total of 112 patients having LBBB pattern on surface electrocardiogram were included (57 with ejection fraction>50% received RVA pacing; 55 had SHF with ejection fraction<35%). Using tissue Doppler imaging, systolic and diastolic dyssynchrony was defined by the standard deviation of the time to peak systolic and peak early diastolic velocity, respectively.
  
  
  RESULTS
  Despite comparable QRS duration and LBBB pattern, the prevalence of electromechanical dyssynchrony was significantly lower in the patients with RVA pacing (systolic: 54% vs 73%, chi2=4.058, P=.044; diastolic: 32% vs 61%, chi2=9.738, P=.002). The presence of coexisting systolic and diastolic dyssynchrony, isolated systolic dyssynchrony, isolated diastolic dyssynchrony, and no dyssynchrony also showed a different distribution between the 2 groups (RVA pacing: 14%, 40%, 18%, and 28%; SHF: 51%, 22%, 11%, and 16%; chi2=17.498, P=.001). Furthermore, the SHF group had a higher prevalence of medial wall (ie, septal, anteroseptal, and inferior) delay (56% vs 30%), whereas RVA pacing resulted in more free wall (ie, lateral, posterior and anterior) delay (44% vs 70%) (chi2=8.050, P=.005).
  
  
  CONCLUSIONS
  The prevalence of mechanical dyssynchrony is lower in patients with normal ejection fraction and RVA pacing when compared with patients with SHF and spontaneous LBBB. The pattern of delay in contraction also appears to be different between the 2 groups.
authors.affiliation: Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.forename: Gabriel Wai-Kwok
authors.initials: GW
authors.lastname: Yip
authors.forename: Joseph Yat-Sun
authors.initials: JY
authors.lastname: Chan
authors.forename: Qing
authors.initials: Q
authors.lastname: Shang
authors.forename: Jeffrey Wing-Hong
authors.initials: JW
authors.lastname: Fung
authors.forename: Anna Kin-Yin
authors.initials: AK
authors.lastname: Chan
authors.forename: Yu-Jia
authors.initials: YJ
authors.lastname: Liang
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000209:etiology / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects; D054143:Heart Failure, Systolic / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D015995:Prevalence