Assessment of reactive hyperaemia using real time zonal echo-planar flow imaging

The measurement of limb blood flow at rest and during reactive hyperaemia has potential as a marker of vascular health and endothelial function because it is the stimulus that causes flow-mediated dilatation, commonly measured as brachial arterial reactivity. Because the flow increases are short lived, they represent a significant challenge for measurement by cardiovascular magnetic resonance. In this study we used a real time, single shot zonal echo-planar imaging method (ZEPI) to study reactive hyperaemia in the femoral artery of five healthy volunteers. Flow velocity was measured every 78 msec. Changes in peak forward flow velocity during systole (580 vs. 390 mm/sec, p < 0.01) and minimum flow velocity (160 vs. 100 mm/sec, p < 0.01) were shown. With progressing improvement in spatial resolution, this technique will allow the accurate noninvasive determination of total flow, flow profile, and peak velocities in real time.