Echocardiographic Speckle Tracking Radial Strain Imaging to Assess Ventricular Dyssynchrony in a Pacing Model of Resynchronization Therapy

Background: Speckle tracking imaging is a promising new echocardiographic method to assess left ventricular (LV) mechanical dyssynchrony. Our aim was to assess a new speckle tracking regional strain algorithm by comparison with angle-corrected tissue Doppler (TD) in an animal model of left bundle branch block and cardiac resynchronization therapy. Methods and Results: Ten open-chest dogs had routine gray-scale and TD images of the mid-LV short-axis plane. Electrical activation was altered by pacing from right ventricular, LV free wall, and biventricular sites to create various degrees of mechanical dyssynchrony and alter regional function. Segmental time to peak strain, peak strain, and frame-by-frame strain were measured by angle-corrected TD, TD M-mode, and speckle tracking on the same digital cineloop. Of 240 possible paired TD and speckle tracking segments, data were available for 222 segments (93%); images with catheter artifacts were prospectively excluded. Comparative overall time to peak strain by each method correlated well: r = 0.96, bias = -6 ± 20 ms. Of 80 possible paired M-mode TD and speckle tracking segments, strain data were available for 76 segments (95%). Comparative overall time to peak strain, peak strain, and frame-by-frame strain analysis in 1012 frames by each method correlated well: r = 0.98, bias of 1 ± 14 ms; r = 0.82, bias of 3% ± 7%; and r = 0.91, bias of 0% ± 6%, respectively. Conclusion: Regional strain analysis using echocardiographic speckle tracking radial strain strongly correlated with strain by angle-corrected TD imaging in an animal model of dyssynchrony. Speckle tracking radial strain has potential for clinical applications.