title: Prevalence and determinants of left ventricular systolic dyssynchrony in patients with normal ejection fraction received right ventricular apical pacing: a real-time three-dimensional echocardiographic study.
abstract: OBJECTIVE
  Right ventricular apical (RVA) pacing may induce mechanical dyssynchrony. However, its impact on patients with normal ejection fraction (EF) is not fully understood. This study examined the prevalence and predictors of RVA pacing-induced systolic dyssynchrony by real-time three-dimensional echocardiography (RT3DE), and evaluated its impact on left ventricular (LV) function.
  
  
  RESULTS
  Ninety-three patients with sinus node dysfunction and normal EF (>50%) received RVA-based dual-chamber pacing were assessed by RT3DE during RVA pacing (V-pace) and intrinsic conduction (V-sense). Systolic dyssynchrony was evaluated using the standard deviation of the time to minimal regional volume of 16 LV segments (Tmsv-16SD), and a cutoff value of 16 ms was determined from 93 normal controls. Systolic dyssynchrony was induced in 49.5% of patients at V-pace with significant increase in LV end-systolic volume (LVESV), decrease in EF, and worsening of Tmsv-16SD (all P < 0.001). Furthermore, patients who developed dyssynchrony had larger LVESV (P < 0.001), lower EF (P < 0.001) at V-pace mode, and higher cumulative percentage of RVA pacing in the past 6 months (P < 0.001) than those without systolic dyssynchrony. In multivariate logistic regression analysis, independent predictors of developing LV systolic dyssynchrony during V-pace included a low normal EF at V-sense, pre-existing LV hypertrophy, and cumulative RVA pacing >40% in the past 6 months.
  
  
  CONCLUSIONS
  For patients with preserved EF received RVA pacing, half of them would develop systolic dyssynchrony which was associated with EF deterioration and LV enlargement. A low normal EF, a high cumulative percentage of RVA pacing, and pre-existing LV hypertrophy were predictors of developing dyssynchrony.
authors.affiliation: Division of Cardiology, Department of Medicine and Therapeutics, Institute of Vascular Medicine, SH Ho Cardiovascular and Stroke Centre, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.forename: Joseph Yat-Sun
authors.initials: JY
authors.lastname: Chan
authors.forename: Gabriel Wai-Kwok
authors.initials: GW
authors.lastname: Yip
authors.forename: Jun-Min
authors.initials: JM
authors.lastname: Xie
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Jeffrey Wing-Hong
authors.initials: JW
authors.lastname: Fung
authors.forename: Yat-Yin
authors.initials: YY
authors.lastname: Lam
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging*; D002304:Cardiac Pacing, Artificial; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D019560:Echocardiography, Three-Dimensional; D005260:Female; D006339:Heart Rate; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015995:Prevalence; D012307:Risk Factors; D012849:Sinoatrial Node; D013318:Stroke Volume; D013599:Systole; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging*; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right