title: Effect of cardiac resynchronization therapy on patients with heart failure and narrow QRS complexes: a meta-analysis of five randomized controlled trials.
abstract: OBJECTIVE
  Although cardiac resynchronization therapy (CRT) has been demonstrated extensively to benefit heart failure (HF) patients with wide QRS complexes, the effect of CRT in patients with narrow QRS complexes remains unclear. This meta-analysis aimed to determine whether HF patients with narrow QRS complexes may benefit from CRT.
  
  
  METHODS
  A search of MEDLINE, EMBASE, and Cochrane databases was performed to identify randomized controlled trials (RCTs) that investigated the effect of CRT in HF patients with narrow QRS complexes (< 130 ms). Outcomes included all-cause mortality, heart failure-related death or hospitalization, 6-min walk distance, quality of life ejection fraction, end-systolic volume, and end-diastolic volume.
  
  
  RESULTS
  A total of five RCTs involving 1246 HF patients with narrow QRS complexes were included. The frequency of all-cause mortality for patients receiving CRT versus the control group was 10 versus 7 % (relative risk [RR] 1.45, 95 % confidence interval [CI] 1.002 to 2.091, P = 0.049). CRT did not reduce heart failure-related mortality (RR 0.89; 95 % CI 0.52 to 1.54; P = 0.69) or hospitalization (RR 0.99, 95 % CI 0.79 to 1.23, P = 0.91). In addition, CRT did not improve average 6-min walk distance (weighted mean difference [WMD] 39.28 m, 95 % CI -71.04 to 149.61 m, P = 0.49), QOL scores (WMD 0.64 points, 95 % CI -2.15.10 to 3.43 points, P = 0.65), or ejection fraction (WMD 0.90 %, 95 % CI -0.71 to 2.51 %, P = 0.28).
  
  
  CONCLUSIONS
  In HF patients with reduced left ventricular ejection fraction (≤ 35 %) and narrow QRS complexes (< 130 ms), CRT did not improve clinical or functional outcomes and may actually increase all-cause mortality.
authors.affiliation: Department of Cardiology, Henan Provincial People's Hospital (People's Hospital of Zhengzhou University), 7 Weiwu Road, Zhengzhou, 450003, China.
authors.forename: Guanggong
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Cardiology, Henan Provincial People's Hospital (People's Hospital of Zhengzhou University), 7 Weiwu Road, Zhengzhou, 450003, China.
authors.forename: Zonglei
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Cardiology, Henan Provincial People's Hospital (People's Hospital of Zhengzhou University), 7 Weiwu Road, Zhengzhou, 450003, China.
authors.forename: Shichao
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Department of Cardiology, Henan Provincial People's Hospital (People's Hospital of Zhengzhou University), 7 Weiwu Road, Zhengzhou, 450003, China.
authors.forename: Shoukun
authors.initials: S
authors.lastname: Ding
authors.affiliation: Department of Cardiology, Henan Provincial People's Hospital (People's Hospital of Zhengzhou University), 7 Weiwu Road, Zhengzhou, 450003, China.
authors.forename: Shuxin
authors.initials: S
authors.lastname: Shen
authors.affiliation: Department of Cardiology, Henan Provincial People's Hospital (People's Hospital of Zhengzhou University), 7 Weiwu Road, Zhengzhou, 450003, China. lixiawang1014@126.com.
authors.forename: Lixia
authors.initials: L
authors.lastname: Wang
mesh_terms: D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D016032:Randomized Controlled Trials as Topic
keywords: Cardiac resynchronization therapy; Heart failure; Meta-analysis; Mortality; Narrow QRS; Randomized controlled trials