Three-directional myocardial motion assessed using 3D phase contrast MRI.

Abstract

Regional myocardial function is a complex entity consisting of motion in three dimensions (3D). Besides magnetic resonance imaging (MRI), no other noninvasive technique can give a true 3D description of cardiac motion. Using a time-resolved 3D phase contrast technique, three-dimensional image volumes containing myocardial velocity data in six normal volunteers were acquired. Coordinates and velocity information were extracted from nine points placed in different myocardial segments in the left ventricle (LV), and decomposed into longitudinal (V(L)), radial (V(R)), and circumferential (V(C)) velocity components. Our findings confirm a longitudinal apex-to-base gradient for the LV, with only a small motion of the apex. The mean velocity for V(L) for all the basal segments was higher compared to the midsegments during systole [3.5+/-1.2 vs. 2.5+/-1.7 cm/s (p<0.01)], early filling [-6.9+/-1.8 vs. -4.9+/-1.8 cm/s (p<0.001)], and during atrial contraction [-2.2+/-1.4 vs. -1.6+/-1.3 cm/s (p<0.05)]. A similar pattern was observed when comparing velocities from the midsegments to the apex. Radial velocity was higher during early filling in the midportion of the lateral [-4.9+/-2.7 vs. -3.2+/-1.6 cm/s (p<0.05)] wall compared to the basal segments, no difference was observed for the septal [-2.0+/-1.5 vs. -0.3+/-2.5 cm/s (p=0.15)], anterior [-5.8+/-3.3 vs. -4.0+/-1.7 cm/s (p=0.17)], and posterior [-2.3+/-2.1 vs. -2.5+/-1.0 cm/s (p=0.78)] walls. When observing the myocardial velocity in a single point and visualizing the movement of the main direction of the velocities in this point as vectors in velocity vector plots like planes, it is clear that myocardial movement is by no means one dimensional. In conclusion, our time-resolved 3D, phase contrast MRI technique makes it feasible to extract myocardial velocities from anywhere in the myocardium, including all three velocity components without the need for positioning any slices at the time of acquisition.