title: Variable patterns of septal activation in patients with left bundle branch block and heart failure.
abstract: BACKGROUND
  Little is known about the septal activation pattern in patients with heart failure and left bundle branch block (LBBB-HF).
  
  
  RESULTS
  The right ventricular (RV) and left ventricular (LV) activation patterns of 12 patients (mean age 67 +/- 11 years) with LBBB-HF and 5 patients (mean age 45 +/- 14) with normal hearts were studied during sinus rhythm using a three-dimensional mapping system. The etiology of HF was myocardial infarction (n = 4) or idiopathic dilated cardiomyopathy (n = 8). In patients with LBBB-HF, endocardial activation usually started before the onset of the surface QRS complex on the RV free wall. Latest RV activation occurred in the basal region, and total RV activation time was longer than in patients with normal hearts. In patients with LBBB-HF, the left septum was activated via slowly conducting LBB or via right-to-left transseptal conduction. In both patients with LBBB-HF and those with normal hearts, latest LV activation occurred either in the posterior or posterolateral-basal region. Conduction velocity was slower in the peri-scar region, in patients with previous myocardial infarct and globally slow, in patients with idiopathic dilated cardiomyopathy.
  
  
  CONCLUSIONS
  The two types of left septal activation observed in patients with LBBB-HF may have consequences for biventricular hemodynamic performance. Conduction slowing along the LV, regionally or globally, suggests a contribution outside the specific conduction system in the ECG pattern of LBBB.
authors.affiliation: Department of Cardiology, Academic Hospital Maastricht, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands. LM.Rodriguez@cardio.unimaas.nl
authors.forename: Luz-Maria
authors.initials: LM
authors.lastname: Rodriguez
authors.forename: Carl
authors.initials: C
authors.lastname: Timmermans
authors.forename: Ashish
authors.initials: A
authors.lastname: Nabar
authors.forename: Graydon
authors.initials: G
authors.lastname: Beatty
authors.forename: Hein J J
authors.initials: HJ
authors.lastname: Wellens
mesh_terms: D000368:Aged; D018780:Body Surface Potential Mapping / Q000379:methods*; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D002311:Cardiomyopathy, Dilated / Q000150:complications; D004699:Endocardium / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D006346:Heart Septum / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications; D009435:Synaptic Transmission