Estimation of the myocardial activation sequence based on B-mode ultrasound cine-images

Non-invasive estimation of the mechanical activation sequence provides valuable diagnostic information on myocardial function. Here, an attempt is made to retrieve it from longitudinal strains calculated from B-mode echocardiographic loops in 3 sheep, paced at 2 sites - lateral and septal, and compare it to normal sequences. B-mode LV basal short-axis images were acquired followed by off-line analysis of Speckle Tracking Imaging by 2D Strain, a customized software application that calculates regional strains. Mechanical activation times were assessed as onset times of circumferential shortening measured from strain profiles, and quantified by the segmental propagation vector (SDV). The time of 90% activation within the ROI of the LV was similar to 60 +/- 5ms for lateral pacing, similar to 65 +/- 5ms for septal pacing vs. similar to 40 +/- 5ms for no-pacing, showing degradation of synchrony. The directivity of the propagation pattern was significantly higher (lower variance) of the SDV in the paced modes.