Measuring peripheral resistance and conduit arterial structure in humans using Doppler ultrasound.

The purpose of this study was to establish valid indexes of conduit and resistance vessel structure in humans by using edge detection and wall tracking of high-resolution B-mode arterial ultrasound images, combined with synchronized Doppler waveform envelope analysis, to calculate conduit artery blood flow and diameter continuously across the cardiac cycle. Nine subjects aged 36.7 (9.2) yr underwent, on separate days, assessment of brachial artery blood flow and diameter response to 5-, 10-, and 15-min periods of forearm ischemia in the presence and absence of combined sublingual glyceryl trinitrate (GTN) administration. Two further sessions examined responses to ischemic exercise, one in combination with GTN. The peak brachial artery diameter was observed in response to the combination of ischemic exercise and GTN; a significant difference existed between resting brachial artery diameter and peak brachial artery diameter, indicating that resting diameter may be a poor measure of conduit vessel structure in vivo. Peak brachial artery flow was also observed in response to a combination of forearm ischemia exercise and GTN administration, the response being greater than that induced by periods of ischemia, GTN, or ischemic exercise alone. These data indicate that noninvasive indexes of conduit and resistance vessel structure can be simultaneously determined in vivo in response to a single, brief, stimulus and that caution should be applied in using resting arterial diameter as a surrogate measure of conduit artery structure in vivo.