title: Left ventricular dyssynchrony from right ventricular pacing depends on intraventricular conduction pattern in intrinsic rhythm.
abstract: OBJECTIVE
  Right ventricular pacing (RVP) prolongs ventricular activation and may induce mechanical dyssynchrony. We hypothesized that the severity of RVP-associated ventricular mechanical dyssynchrony may depend on the intrinsic intraventricular conduction pattern.
  
  
  RESULTS
  Sixty-five patients with a single- or dual-chamber RV pacemaker were included. Forty-seven patients with ejection fraction (EF) <or= 35%, 17 with no bundle branch block (BBB), 16 with right bundle branch block (RBBB), and 14 with left bundle branch block (LBBB). Eighteen patients with EF > 35% and no BBB served as a control group. Echocardiographic dyssynchrony parameters [aortic pre-ejection delay (AoPEP), interventricular mechanical delay, delayed posterior left ventricular wall motion, and septal-to-posterior wall motion delay (SPWMD)] were evaluated in all patients with and without RVP. No dyssynchrony was found in patients with no BBB, RBBB, and in the control group, whereas LBBB patients showed significant dyssynchrony in AoPEP and SPWMD. RVP had a significant negative impact on all dyssynchrony parameters in patients with no BBB or LBBB. RVP induced significantly less severe dyssynchrony in RBBB patients. With RVP 100, 94, 56 and 16% of patients with LBBB, without BBB, RBBB, and from the control group, respectively, fulfilled the CARE-HF criteria for ventricular dyssynchrony.
  
  
  CONCLUSIONS
  RVP worsens mechanical ventricular dyssynchrony in patients with reduced EF. These effects are most pronounced in patients with either normal QRS width or LBBB during intrinsic rhythm. In contrast, patients with an RBBB during intrinsic rhythm without RVP evidenced a better preserved haemodynamic function and mechanical synchrony with RVP, despite a comparable extent of pacing-induced QRS prolongation.
authors.affiliation: Department of Cardiology, Klinikum Coburg, DE-96450 Coburg, Germany. mschmidtco@arcor.de
authors.forename: Martin
authors.initials: M
authors.lastname: Schmidt
authors.forename: Harald
authors.initials: H
authors.lastname: Rittger
authors.forename: Harald
authors.initials: H
authors.lastname: Marschang
authors.forename: Anil-Martin
authors.initials: AM
authors.lastname: Sinha
authors.forename: Marcos
authors.initials: M
authors.lastname: Daccarett
authors.forename: Johannes
authors.initials: J
authors.lastname: Brachmann
authors.forename: Michael
authors.initials: M
authors.lastname: Block
authors.forename: Ole A
authors.initials: OA
authors.lastname: Breithardt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002037:Bundle-Branch Block / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D015150:Echocardiography, Doppler / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013318:Stroke Volume; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology*