Figure 3

Flow velocity measurements in the left ventricular outflow tract by CMR. Panel A shows the change in peak left ventricular outflow tract (LVOT) velocity at -12 mm position during the cardiac cycle. Panel B shows the change in the instantaneous average velocity obtained over the region of interest. The velocity-time integral (VTI) is the area under the curve. Panel C shows the change in instantaneous flow (Q) calculated as follows: Q (t) = average velocity (t) × A_LVOT, where A_LVOT is the cross-sectional area of the LVOT. The stroke volume (SV) is the flow-time integral during systole. Panel D shows the change in peak aortic velocity at +6 mm position during the cardiac cycle, the velocity-time integral (VTI) is the area under the curve.