Background:
We previously reported that the inertia force (IF) of blood flowing out of left ventricle (LV) during late-systole produces greater LV elastic recoil force and brings faster LV relaxation. Vector flow mapping (VFM
TM
, Hitachi-Aloka) enables us to see blood flow velocity vectors that are generated from conventional color Doppler imaging data at any phase of cardiac cycle without angle dependency. Using VFM, kinetic energy (KE) of ejecting blood flow during systole at the LV outflow tract (LVOT) can be obtained. Thus, we investigated whether the KE obtained at the LVOT during late systole (KE-ls) had any relations with the IF and invasively obtained LV function parameters.
Method:
Study subjects were 33 patients who underwent diagnostic cardiac catheterization and echocardiographic examination on the same day. Color Doppler images were acquired in the apical 3-chamber view. The frame rate ranged was from 40 to 51 frames per minute. Data analyses were performed offline using the commercially available software (DAS-RS1
TM,
Hitachi-Aloka). A data sampling area was set at the level just below the aortic valve in the LVOT. The KE-ls was computed as the sum of KE values computed in frame by frame basis during late-systole; late-systole was defined as the latter one-third of ejecting time. LV pressure wave was obtained using a catheter-tipped micromanometer, and then, the first derivative of LV pressure (dP/dt) and a time constant τ of LV pressure decay during isovolumic relaxation were calculated. From LV pressure-dP/dt relationships (phase loop), the IF was determined.
Results:
A significant positive correlation was observed between the KE-ls and the IF (r=0.79, p<0.0001). The log transformed KE-ls had significant correlations with both peak negative dP/dt (r=0.53, p<0.01) and the time constant τ (r=-0.67, p<0.0001).
Conclusion:
VFM is a new useful technique to see blood flow in the LV chamber. Noninvasively obtained KE-ls using VFM, which may be a noninvasive surrogate for the IF, has significant correlations with the parameters of LV relaxation.
Intraventricular vector flow mapping by 3-D doppler echo