Evaluation of arterial endothelial function using transit times of artificially induced pulses

Arterial endothelial dysfunction is an early event in atherosclerosis and correlates with cardiovascular disease risk factors. The most widely used noninvasive measure of endothelial function involves brachial artery (BA) diameter measurement using ultrasound imaging. The change in arterial diameter after reactive hyperemia is a measure of endothelium-mediated vasorelaxation (EMVR). High technical complexity and cost render this technique unsuitable for routine clinical use. To assess EMVR we induce artificial pulses at the superficial radial artery using a linear actuator. An ultrasonic flowmeter detects these pulses 10-30 cm proximal to the point of induction. The delay between pulse application and detection provides the pulse transit time (PTT). By measuring PTT before and after BA occlusion and ensuing reactive hyperemia, EMVR can be quantified since smooth muscle relaxation increases PTT. This method is shown to provide 37% greater sensitivity (p<0.05) to EMVR than BA diameter measurement in the eleven human subjects examined.