title: Dyssynchrony and the risk of ventricular arrhythmias.
abstract: OBJECTIVE
  The aim of our study was to evaluate the relationship between left ventricular (LV) dyssynchrony and the risk of ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients enrolled in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy) trial.
  
  
  BACKGROUND
  Intraventricular mechanical dyssynchrony might be an important factor in ventricular arrhythmogenesis by enhancing electrical heterogeneity in heart failure patients. The effects of dyssynchrony have not yet been evaluated in a large cohort of implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy with defibrillator (CRT-D) patients.
  
  
  METHODS
  LV dyssynchrony was measured at baseline and at 12-months by speckle-tracking echocardiography, defined as the standard deviation of time to peak systolic strain in 12 LV myocardial segments. The endpoint was the first VT/VF/death or VT/VF. LV dyssynchrony was evaluated in 764 left bundle branch block (LBBB) patients and in 312 non-LBBB patients.
  
  
  RESULTS
  Baseline LV dyssynchrony was not predictive of VT/VF/death or VT/VF in LBBB or non-LBBB patients in either treatment arm. In CRT-D patients with LBBB, improvement in LV dyssynchrony over a year was associated with significantly lower incidence of VT/VF/death (p < 0.001) and VT/VF (p < 0.001) compared to ICD patients and to CRT-D patients with unchanged or worsening dyssynchrony. Among LBBB patients, 15% decrease in LV dyssynchrony was associated with lower risk of VT/VF/death (hazard ratio: 0.49, 95% confidence interval: 0.24 to 0.99, p = 0.049) and VT/VF (hazard ratio: 0.30, 95% confidence interval: 0.12 to 0.77, p = 0.009) as compared to ICD patients. Patients without LBBB receiving CRT-D did not show reduction in VT/VF/death or in VT/VF in relation to improving dyssynchrony when evaluating cumulative event rates or risk of events.
  
  
  CONCLUSIONS
  Baseline LV dyssynchrony did not predict VT/VF/death or VT/VF in mild heart failure patients with or without LBBB. CRT-induced improvement of LV dyssynchrony was associated with significant reduction of ventricular arrhythmias in patients with LBBB.
authors.affiliation: University of Rochester Medical Center, Rochester, New York, USA. valentina.kutyifa@heart.rochester.edu
authors.forename: Valentina
authors.initials: V
authors.lastname: Kutyifa
authors.forename: Anne-Catherine
authors.initials: AC
authors.lastname: Pouleur
authors.forename: Dorit
authors.initials: D
authors.lastname: Knappe
authors.forename: Amin
authors.initials: A
authors.lastname: Al-Ahmad
authors.forename: Michal
authors.initials: M
authors.lastname: Gibinski
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Wang
authors.forename: Scott
authors.initials: S
authors.lastname: McNitt
authors.forename: Bela
authors.initials: B
authors.lastname: Merkely
authors.forename: Ilan
authors.initials: I
authors.lastname: Goldenberg
authors.forename: Scott D
authors.initials: SD
authors.lastname: Solomon
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Moss
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000209:etiology / Q000503:physiopathology; D002170:Canada; D058406:Cardiac Resynchronization Therapy; D058409:Cardiac Resynchronization Therapy Devices; D016009:Chi-Square Distribution; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000295:instrumentation; D005060:Europe; D005260:Female; D006333:Heart Failure / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000209:etiology* / Q000401:mortality / Q000503:physiopathology / Q000517:prevention & control; D013997:Time Factors; D016896:Treatment Outcome; D014463:Ultrasonography; D014481:United States; D018487:Ventricular Dysfunction, Left / Q000150:complications* / Q000000981:diagnostic imaging / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D014693:Ventricular Fibrillation / Q000209:etiology* / Q000401:mortality / Q000503:physiopathology / Q000517:prevention & control; D016277:Ventricular Function, Left