Background: Velocity Vector Imaging (VVI), which is based on myocardial feature tracking that incorporates speckle and endocardial border tracking, allows for the quantitation of myocardial strain, strain rate and velocity. However, compared with conventional speckle tracking echocardiography (STE), the accuracy of VVI-derived LV rotation-associated values has not been validated extensively.
Methods: 25 patients with a wide spectrum of cardiac pathologies (10 with dilated cardiomyopathy, 10 with hypertrophic cardiomyopathy and 5 with severe aortic stenosis) and 25 healthy controls were enrolled to cover a broad clinical range of LV rotation values. The apical and basal short-axis images were obtained from GE Vivid 7 scanners at a frame rate of 80~100. LV rotation-related parameters were first obtained using EchoPAC PC 7.0.0. For comparison, the same basal and apical short-axis images were converted into DICOM format without compression, which was subsequently analyzed using Syngo 3.0 software that employs VVI tracking algorithm.
Results: Basal peak clockwise rotation was -4.5짹1.3 and -4.2짹1.5째 (p=NS) by STE and VVI, respectively. Linear regression analysis for basal peak rotation showed a significant correlation between the methods (R=0.69, p=0.009). Peak initial counter-clockwise rotation of the basal myocardium had no correlation, but its duration showed good correlation (R=0.88, p<0.001) between methods with shorter values by VVI. With regard to basal twist and untwist rate, the peak velocities and time to peak velocities were well correlated between methods. Peak apical rotation were 15.9짹3.7째 for STE and 13.8짹4.0째 for VVI (p=NS), and displayed a good correlation between the 2 methods (R=0.78, p=0.003). However, the apical initial clockwise rotation, twist and untwisting rate were poorly correlated between the 2 methods.
Conclusions: VVI, a new feature-tracking method, can provide a reliable value for peak torsion. However, some values reflecting events during isovolumic period did not correlate well with those obtained by conventional STE. Therefore, care must be exercised to interpret or compare rotation-related values derived from different vendors.