title: Cardiac-resynchronization therapy in patients with systolic heart failure and QRS interval ≤130 ms: insights from a meta-analysis.
abstract: OBJECTIVE
  Cardiac-resynchronization therapy (CRT) reduces morbidity and mortality in patients with chronic systolic heart failure (SHF) and a wide QRS complex. It is unclear whether the same benefit extends to patients with QRS duration (QRSd) <130 ms.
  
  
  RESULTS
  Our aim was to perform a meta-analysis of all randomized controlled trial (RCTs) and to evaluate the effect of implantable CRT defibrillator(CRTD) on all-cause mortality, HF mortality, and HF hospitalization in patients with QRSd <130 ms. We performed a systematic literature search to identify all RCTs, comparing CRTD therapy with implantable cardiac defibrillator (ICD) therapy in patients with SHF (ejection fraction <35%) and QRS ≤130 ms, published in Pubmed, Medline, EMBASE, Cochrane library, and Google scholar from June 1980 through June 2013. The search terms included CRT, QRS duration, narrow QRS, clinical trial, RCT, biventricular pacing, heart failure, systolic dysfunction, dyssynchrony, left ventricular remodelling, readmission, mortality, survival, and various combinations of these terms. We studied the trends of overall mortality, SHF mortality, and hospitalizations due to SHF between the two groups. Heterogeneity of the studies was analysed by Q statistic. A fixed-effect model was used to compute the relative risk (RR) of mortality due to SHF, while a random-effects model was used to compare hospitalization due to SHF. Out of a total of 12 100 citations, four RCTs comparing CRTD vs. ICD therapy in patients with SHF and QRS ≤130 ms fulfilled the inclusion criteria. The median follow-up was 12 months and the cumulative number of patients was 1177. Relative Risk for all-cause mortality in patients treated with CRTD was 1.66 with a 95% CI of 1.096-2.515 (P = 0.017) while for SHF mortality was 1.29 with 95% CI of 0.68-2.45 (P = 0.42). Relative risk for HF hospitalization in patients treated with CRTD was 0.94 with 95% CI of 0.50-1.74 (P = 0.84) in comparison to the ICD group.
  
  
  CONCLUSIONS
  Cardiac-resynchronization therapy defibrillator has no impact on SHF mortality and SHF hospitalization in patients with systolic HF with QRS duration ≤130 ms and is associated with higher all-cause mortality in comparison with ICD therapy.
authors.affiliation: Cardiac Electrophysiology, Department of Cardiology, Virginia Commonwealth University Hospital, Gateway Building, 3rdFl, PO Box 980053, Richmond, VA 23298-0053, USA.
authors.forename: Rachit M
authors.initials: RM
authors.lastname: Shah
authors.affiliation: Cardiac Electrophysiology, Department of Cardiology, Virginia Commonwealth University Hospital, Gateway Building, 3rdFl, PO Box 980053, Richmond, VA 23298-0053, USA.
authors.forename: Dhavalkumar
authors.initials: D
authors.lastname: Patel
authors.affiliation: Department of Cardiology, Rosalind Franklin University, North Chicago, IL, USA.
authors.forename: Janos
authors.initials: J
authors.lastname: Molnar
authors.affiliation: Cardiac Electrophysiology, Department of Cardiology, Virginia Commonwealth University Hospital, Gateway Building, 3rdFl, PO Box 980053, Richmond, VA 23298-0053, USA.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
authors.affiliation: Cardiac Electrophysiology, Department of Cardiology, Virginia Commonwealth University Hospital, Gateway Building, 3rdFl, PO Box 980053, Richmond, VA 23298-0053, USA jkoneru@mcvh-vcu.edu.
authors.forename: Jayanthi N
authors.initials: JN
authors.lastname: Koneru
mesh_terms: D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D058409:Cardiac Resynchronization Therapy Devices; D016757:Death, Sudden, Cardiac / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D054143:Heart Failure, Systolic / Q000401:mortality / Q000628:therapy*; D006760:Hospitalization; D006801:Humans; D016896:Treatment Outcome
keywords: All-cause mortality; CRT; HF hospitalization; HF mortality; LV dyssynchrony; QRS duration