title: Prolonged QRS duration (QRS >/=170 ms) and left axis deviation in the presence of left bundle branch block: A marker of poor left ventricular systolic function?
abstract: BACKGROUND
  Left bundle branch block (LBBB) is commonly associated with structural heart disease and left ventricular dysfunction. We propose that the QRS duration and degree of left-axis deviation (LAD) identify significant left ventricular systolic dysfunction in patients with LBBB.
  
  
  METHODS
  In this prospective study the ejection fraction (EF) of 300 consecutive patients with LBBB was evaluated by echocardiography. The relationship between QRS duration and LAD (axis between -30 degrees and -90 degrees ) and EF were derived.
  
  
  RESULTS
  There was no significant difference in age, sex, presence of ischemic or nonischemic cardiomyopathy and valvular heart disease, and EF among the patients with or without LAD. The EF of patients with QRS >/=170 milliseconds with LAD (n = 20) and without LAD (n = 18) was 25% +/- 16% and 23% +/- 13%, respectively (P =.71). The mean EF (24% +/- 10%) of the patients with a QRS duration of >/=170 milliseconds (n = 38) was significantly lower than the mean EF (36% +/- 16%) of the patients with a QRS duration of <170 milliseconds (n = 262, P <.015). The QRS duration also had a significant (P <.001) inverse correlation with EF (R = 0.37, adjusted R (2) = 0.13, SE of estimate = 16.21). However, the QRS axis was not significantly correlated with EF and did not have added predictive value.
  
  
  CONCLUSIONS
  The QRS duration has a significant inverse relationship with EF and prolongation of QRS duration (>/=170 milliseconds) in the presence of LBBB is a marker of significant left ventricular systolic dysfunction. The presence of LAD in LBBB does not signify a further decrease in EF.
authors.affiliation: New York Presbyterian Hospital-Cornell University Medical College, New York, NY 10021, USA. mithileshdas@hotmail.com
authors.forename: M K
authors.initials: MK
authors.lastname: Das
authors.forename: K
authors.initials: K
authors.lastname: Cheriparambil
authors.forename: A
authors.initials: A
authors.lastname: Bedi
authors.forename: J
authors.initials: J
authors.lastname: Kassotis
authors.forename: C V
authors.initials: CV
authors.lastname: Reddy
authors.forename: M
authors.initials: M
authors.lastname: Makan
authors.forename: C C
authors.initials: CC
authors.lastname: Dunbar
authors.forename: B
authors.initials: B
authors.lastname: Saul
mesh_terms: D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000453:epidemiology; D015897:Comorbidity; D004452:Echocardiography; D004562:Electrocardiography / Q000706:statistics & numerical data*; D006801:Humans; D011446:Prospective Studies; D013318:Stroke Volume / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000453:epidemiology