Abstract 526: Radiofrequency-based Speckle Tracking Echocardiography Using a Newly Developed Prototype Ultrasound System for Evaluation of Myocardial Strain and Strain Rate
Introduction: Current commercially available 2D speckle tracking techniques operate at relatively low speckle tracking frame rates (<100 frames/sec) and utilize only the processed 2D B-mode data rather than the raw radiofrequency (RF) ultrasound data. We have developed a prototype RF-based speckle tracking echocardiography system that operates at high speckle tracking frame rates (>500 frames/sec), with an effective temporal resolution of 60 to 150 frames/sec. This prototype uses the raw RF data (including the signal phase information) to improve tracking quality.
Methods: 24 human subjects (10 normal and 14 with known CAD) underwent imaging with the prototype system. Longitudinal end-systolic strain (ϵ), peak systolic strain rate (sSR), and peak early diastolic strain rate (dSR) were measured in each of 18 segments derived from 3 standard apical views. Global ϵ, sSR, and dSR were also calculated for each subject by averaging the 18 segments. Narrow sector imaging was also compared to full sector imaging.
Results: ϵ, sSR, and dSR could be obtained in 94%, 92%, and 92% of segments, respectively. Among normal subjects, the mean ϵ, sSR, and dSR varied significantly by segment, with the lowest values found in the apical segments of the anterior, anteroseptal, and lateral walls. Subjects with CAD had significantly lower global ϵ (−8.3±3.0% vs. −16.5±2.2%, p <0.001), sSR (−0.53±0.19 s−1 vs. −1.11±0.17 s−1, p <0.001), and dSR (0.61±0.23 s−1 vs. 1.58±0.31 s−1, p <0.001) compared to normal subjects. Among subjects with CAD, segments with an abnormal wall motion score (WMS) had significantly lower ϵcompared to those with a normal WMS (−6.3±5.5% vs. −9.9±7.0%, p = 0.009), and a trend toward lower sSR (p = 0.076). In addition, the mean ϵ, sSR, and dSR of normal segments from patients with CAD were significantly lower than those from normal subjects (p <0.001 for each parameter). Narrow sector imaging did not improve the results.
Conclusions: Radiofrequency-based speckle tracking echocardiography using the new prototype is feasible and allows for evaluation of myocardial strain and strain rate. This new prototype can successfully detect abnormalities secondary to CAD, and has significant potential to improve the echocardiographic assessment of myocardial deformation.