Abstract 15751: Detecting the Onset of Contraction Using High Frame Rate Strain Rate Images

IntroductionDeriving timing data from high frame rate ultrasound images can be difficult, as the image quality decreases as frame rate increases. However, higher temporal resolution increases the information quality. This means that as ultrasound systems become capable of higher frame rates, they are able to detect and track fast moving propagating wave fronts such as the propagation of mechanical contraction of the left ventricle. Here we show derived timing data which enables the visualization of propagating waves associated with contraction.Methods2D B-mode images from 5 patients with conduction disorders and with biventricular pacemakers were acquired at 500-1000 images per second using Duke University’s phased array ultrasound system, T5. Strain rate images were derived from the ultrasound images. After identifying the biventricular pacing, we then look for the first tissue shortening wave front within the strain rate images. The earliest locations on the wave was identified as the onset of contraction, see Figure 1.ResultsTwo cardiologists analyzed the strain rate images and defined the location of the pacing lead by using strain rate images. Angiographs were used to verify the locations of the pacing leads. In 4 of 5 cases the location identified in the strain rate images agreed with the pacing lead locations. However, in the 5, infarcted tissue was being paced.ConclusionsPacing a heart using a biventricular pacer causes a wave front immediately after the electrical pacing spike, which propagates from the pacing lead location in interventricular septum. By using high frame rate strain rate images, it was possible to find earliest point of the wave fronts which was associated with the location of excitation.Figure 1 shows the strain rate image of a left bundle branch block patient. The onset and propagation of contraction caused by the RV pacing lead of a biventricular pacemaker is marked by the green star and line respectfully.