title: Quantitative assessment of strain and strain rate by velocity vector imaging during dobutamine stress echocardiography to predict outcome in patients with left bundle branch block.
abstract: BACKGROUND
  Abnormal septal motion in left bundle branch block (LBBB) may compromise the interpretation of regional wall motion. Velocity vector imaging (VVI) has been proposed as an objective method to quantify regional myocardial deformation. The aim of this study was to determine whether VVI during dobutamine stress echocardiography (DSE) has prognostic value in patients with LBBB.
  
  
  METHODS
  In 84 patients with (mean age, 75 +/- 9 years) undergoing DSE, longitudinal peak systolic strain (epsilon(sys)) and strain rate (SR(sys)) were measured in 16 segments using VVI. Results were expressed as average SR(sys) and epsilon(sys) per patient. Follow-up was obtained for the combined endpoint of mortality, myocardial infarction, and coronary revascularization. Contributions of clinical, conventional dobutamine stress echocardiographic, and epsilon(sys) and SR(sys) variables to outcome were assessed using Cox models.
  
  
  RESULTS
  During a mean follow-up period of 18.3 +/- 13.8 months, 23 patients had endpoints. Wall motion score index at rest was the only independent predictor in a model combining clinical and conventional dobutamine stress echocardiographic variables. However, when epsilon(sys) and SR(sys) variables were considered, average SR(sys) at peak stress (hazard ratio, 2.38 per 0.2/s increment; 95% confidence interval, 1.53-3.88; P < .0001) became the only independent predictor of outcome. Using average SR(sys) at peak of -0.5/s as the cut point maximized the model chi(2) value for the prediction of outcomes (model chi(2) = 18.71, P = .002). The annualized event-free survival in patients with average SR(sys) at peak stress lower and higher than -0.5/s were 89.9% and 45.9%, respectively (P < .0001).
  
  
  CONCLUSIONS
  Average SR(sys) at peak stress during DSE offers prognostic information incremental to wall motion analysis in patients with LBBB.
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Shan
authors.forename: Hector R
authors.initials: HR
authors.lastname: Villarraga
authors.forename: Cristina
authors.initials: C
authors.lastname: Pislaru
authors.forename: Aijaz A
authors.initials: AA
authors.lastname: Shah
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Cha
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Pellikka
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000000981:diagnostic imaging* / Q000401:mortality / Q000503:physiopathology; D016009:Chi-Square Distribution; D025401:Echocardiography, Stress; D005260:Female; D006801:Humans; D008297:Male; D011379:Prognosis; D016016:Proportional Hazards Models; D015203:Reproducibility of Results; D012307:Risk Factors