774-5 Effect of Cardiac Translation on Measurement of Left Ventricular Wall Velocities: Implications for Doppler Imaging of Myocardium

Abstract

Doppler imaging of the myocardium is a new application which has the potential to record myocardial velocities. These recorded velocities, however, include cardiac motion independent of ventricular contraction. A measured myocardial velocity, therefore, represents the net vector of contraction, translation, and rotation. To determine the effects of cardiac translation on myocardial velocities, 2-dimensional (2D) and M-mode echocardiographic recordings were obtained in 10 normal subjects. The average anteroseptal (AS) and posterior wall (PW) velocities were measured by 2D echo directed M-mode in the centerline of the parasternal short-axis view. Translation was measured from 2D echo cine-loop display as the displacement of the epicardial junction of the right ventricular free wall and interventricular septum during systole. The average translational velocity is reported as the component of the displacement vector parallel to the M-mode beam (+ = toward transducer). The AS and PW velocities (cm/sec) displayed in the table represent net measured velocities, which include the translational vector. AS PW Translation Mean ± SD 3.2 ± 0.5 4.5 ± 1.1 +1.3 ± 0.6 Range 2.4 to 4.0 3.4 to 6.9 -l.4 to + 2.4 In 8/10 subjects the velocity vector was positive. The mean percent error in the M-mode derived velocities due to translation was 41% for the AS wall and 31% for the PW. 1) As measured by 2D echocardiography, the magnitude of the translational vector is significant when compared to the M-mode derived myocardial velocities. 2) The relative error demonstrated in the measured velocities may be further modified when applied in two dimensions, due to the angle of incidence of the Doppler beam. 3) New techniques for measuring myocardial velocities, such as Doppler imaging of the myocardium, should incorporate algorithms which correct for the translational vector.