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

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 (ε{lunate}_sys) and strain rate (SR_sys) were measured in 16 segments using VVI. Results were expressed as average SR_sys and ε{lunate}_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 ε{lunate}_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 ε{lunate}_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 χ² value for the prediction of outcomes (model χ² = 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). Conclusion: Average SR_sys at peak stress during DSE offers prognostic information incremental to wall motion analysis in patients with LBBB.