title: Biventricular pacing in patients with bradycardia and normal ejection fraction.
abstract: BACKGROUND
  Observational studies suggest that conventional right ventricular apical pacing may have a deleterious effect on left ventricular function. In this study, we examined whether biventricular pacing is superior to right ventricular apical pacing in preventing deterioration of left ventricular systolic function and cardiac remodeling in patients with bradycardia and a normal ejection fraction.
  
  
  METHODS
  In this prospective, double-blind, multicenter study, we randomly assigned 177 patients in whom a biventricular pacemaker had been successfully implanted to receive biventricular pacing (89 patients) or right ventricular apical pacing (88 patients). The primary end points were the left ventricular ejection fraction and left ventricular end-systolic volume at 12 months.
  
  
  RESULTS
  At 12 months, the mean left ventricular ejection fraction was significantly lower in the right-ventricular-pacing group than in the biventricular-pacing group (54.8+/-9.1% vs. 62.2+/-7.0%, P<0.001), with an absolute difference of 7.4 percentage points, whereas the left ventricular end-systolic volume was significantly higher in the right-ventricular-pacing group than in the biventricular-pacing group (35.7+/-16.3 ml vs. 27.6+/-10.4 ml, P<0.001), with a relative difference between the groups in the change from baseline of 25% (P<0.001). The deleterious effect of right ventricular apical pacing occurred in prespecified subgroups, including patients with and patients without preexisting left ventricular diastolic dysfunction. Eight patients in the right-ventricular-pacing group (9%) and one in the biventricular-pacing group (1%) had ejection fractions of less than 45% (P=0.02). There was one death in the right-ventricular-pacing group, and six patients in the right-ventricular-pacing group and five in the biventricular-pacing group were hospitalized for heart failure (P=0.74).
  
  
  CONCLUSIONS
  In patients with normal systolic function, conventional right ventricular apical pacing resulted in adverse left ventricular remodeling and in a reduction in the left ventricular ejection fraction; these effects were prevented by biventricular pacing. (Centre for Clinical Trials number, CUHK_CCT00037.)
authors.affiliation: Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong. cmyu@cuhk.edu.hk
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
authors.forename: Joseph Yat-Sun
authors.initials: JY
authors.lastname: Chan
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Razali
authors.initials: R
authors.lastname: Omar
authors.forename: Gabriel Wai-Kwok
authors.initials: GW
authors.lastname: Yip
authors.forename: Azlan
authors.initials: A
authors.lastname: Hussin
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.forename: Kai Huat
authors.initials: KH
authors.lastname: Lam
authors.forename: Hamish Chi-Kin
authors.initials: HC
authors.lastname: Chan
authors.forename: Jeffrey Wing-Hong
authors.initials: JW
authors.lastname: Fung
mesh_terms: D000368:Aged; D054537:Atrioventricular Block / Q000150:complications; D001919:Bradycardia / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects / Q000379:methods*; D002306:Cardiac Volume; D004311:Double-Blind Method; D019560:Echocardiography, Three-Dimensional; D005260:Female; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D011446:Prospective Studies; D011788:Quality of Life; D012804:Sick Sinus Syndrome / Q000150:complications; D013318:Stroke Volume; D018487:Ventricular Dysfunction, Left / Q000209:etiology* / Q000517:prevention & control / Q000628:therapy; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling