title: Early pacing-induced systolic dyssynchrony is a strong predictor of left ventricular adverse remodeling: analysis from the Pacing to Avoid Cardiac Enlargement (PACE) trial.
abstract: BACKGROUND
  Right ventricular apical (RVA) pacing is associated with adverse left ventricular (LV) remodeling and biventricular (BiV) pacing may prevent it although the mechanisms remain unclear. The current study aimed to assess the role of early pacing-induced systolic dyssynchrony (DYS) to predict adverse LV remodeling.
  
  
  METHODS
  Patients with standard pacing indications and normal LV ejection fraction were randomized either to BiV (n=89) or RVA pacing (n=88). Pacing-induced DYS, defined as the standard deviation of the time to peak systolic velocity (Dyssynchrony Index) >33 ms in a 12-segmental model of LV, was measured by tissue Doppler echocardiography at 1 month.
  
  
  RESULTS
  At 1 month, 59 patients (33%) had DYS which was more prevalent in RVA than BiV pacing group (52% vs. 15%, χ(2)=28.3, p<0.001), though Dyssynchrony Index was similar at baseline (30 ± 14 vs. 26 ± 11 ms, p=0.06). At 12 months, those developing DYS had significantly lower LV ejection fraction (55.1 ± 9.7 vs. 62.2 ± 7.9%, p<0.001) and larger LV end-systolic volume (35.3 ± 14.3 vs. 27.0 ± 10.4 ml, p<0.001) when compared to those without DYS. Reduction of ejection fraction ≥ 5% occurred in 67% (39 out of 58) of patients with DYS, but only in 18% (21 out of 115) in those without DYS (χ(2)=40.8, p<0.001). Both DYS at 1 month (odds ratio [OR]: 4.725, p=0.001) and RVA pacing (OR: 3.427, p=0.009) were independent predictors for reduction of ejection fraction at 12 months.
  
  
  CONCLUSIONS
  Early pacing-induced DYS is a significant predictor of LV adverse remodeling and the observed benefit of BiV pacing may be related to the prevention of DYS.
  
  
  BACKGROUND
  Centre for Clinical Trials number, CUHK_CCT00037 (URL: http://www.cct.cuhk.edu.hk/Registry/publictrialrecord.aspx?trialid=CUHK_CCT00037).
authors.affiliation: Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Joseph Yat-Sun
authors.initials: JY
authors.lastname: Chan
authors.forename: Omar
authors.initials: O
authors.lastname: Razali
authors.forename: Hussin
authors.initials: H
authors.lastname: Azlan
authors.forename: Hamish Chi-Kin
authors.initials: HC
authors.lastname: Chan
authors.forename: John E
authors.initials: JE
authors.lastname: Sanderson
authors.forename: Jun-Min
authors.initials: JM
authors.lastname: Xie
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D006332:Cardiomegaly / Q000175:diagnosis* / Q000503:physiopathology* / Q000517:prevention & control; D004311:Double-Blind Method; D005260:Female; D006306:Health Surveys / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013599:Systole / Q000502:physiology; D013997:Time Factors; D020257:Ventricular Remodeling / Q000502:physiology*