title: Metaanalysis on effects of cardiac resynchronization therapy in heart failure patients with narrow QRS complex.
abstract: BACKGROUND
  To systematically review the benefits of cardiac resynchronization therapy (CRT) in heart failure patients with narrow QRS (< 120 ms) who have baseline mechanical asynchrony.
  
  
  METHODS
  We searched the MEDLINE, Cochrane Central Register of Controlled Trials, and reference lists of retrieved articles for relevant trials through October 2007. Studies were included if they were clinical trials in heart failure patients with narrow QRS complex, had at least 3 months of duration and measured baseline mechanical dyssynchrony. Weighted mean difference (WMD) for changes in left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) class and 6 minute walk distance (6MWD) at the end of follow up period were estimated using fixed effects meta-analysis.
  
  
  RESULTS
  Three relevant clinical trials (enrolling 98 patients) out of 80 identified studies were included in the final analysis. When compared to baseline, CRT in heart failure patients with narrow QRS complex significantly improved mean LVEF (WMD 7.98%, 95% CI 5.94, 10.03) and 6MWD (WMD 67 m, 95% CI 39.12, 94.98) at the end of follow up period with no significant heterogeneity between the included studies (I(2) < 50%). Similarly, there was a significant reduction in NYHA at the end of follow-up (WMD -0.87, 95% CI -1.01, -0.74) but there was significant heterogeneity between the included studies.
  
  
  CONCLUSIONS
  In patients with narrow QRS complex and baseline mechanical asynchrony, who underwent CRT after optimal medical management, there was a significant reduction in NYHA class, improvement in LVEF and increase in 6MWD during follow up. Further data from large randomized trials are warranted to explore the role of CRT in heart failure patients with narrow QRS complex.
authors.affiliation: General Internal Medicine, Wake Forest University Health Sciences, Medical Center Blvd, Winston-Salem, NC 27157, USA. vjeevanantham@gmail.com
authors.forename: Vinodh
authors.initials: V
authors.lastname: Jeevanantham
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.forename: Sankar
authors.initials: S
authors.lastname: Navaneethan
authors.forename: David
authors.initials: D
authors.lastname: Fitzgerald
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
authors.forename: Augusto
authors.initials: A
authors.lastname: Achilli
authors.forename: Jeroen
authors.initials: J
authors.lastname: Bax
authors.forename: James
authors.initials: J
authors.lastname: Daubert
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System; D006333:Heart Failure / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D013318:Stroke Volume; D016896:Treatment Outcome