Ultrasound Assessment of Flow-Mediated Dilation of the Brachial and Superficial Femoral Arteries in Rats

Abstract

Arterial vasodilation to increases in wall shear rate is indicative of vascular endothelial function. In humans, the non-invasive measurement of endothelial function can be achieved by employing the flow-mediated dilation technique, typically performed in the brachial or superficial femoral artery. Briefly, a blood pressure cuff placed distal to an ultrasound probe is inflated to a suprasystolic pressure, which results in limb ischemia. After 5 min of occlusion the cuff is deflated, resulting in reactive hyperemia and increases in wall shear rate that signal vasodilatory molecules to be released from the endothelium eliciting vasodilation. Despite the thousands of studies performing flow-mediated dilation in humans, surprisingly, no studies have performed this technique non-invasively in living rats. Considering the recent shift in focus to translational research, the establishment of guidelines for non-invasive measurement of flow-mediated dilation in rats and other rodents would be extremely valuable. In the following article, a protocol is presented for the non-invasive measurement of flow-mediated dilation in brachial and superficial femoral arteries of rats, as those sites are most commonly measured in humans. Video LinkThe video component of this article can be found at

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“…Ultrasound imaging of FMD was conducted in the femoral artery, as described in Machin et al ( 18 ). Briefly, rats were anesthetized as described above, the leg was shaved, and a 10 mm occlusion cuff (Holly Specialty Products, USA), inflatable with water, was placed on the ankle.…”

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“…NO-mediated EDD can be determined in pre-clinical models by assessing changes in artery diameter in response to flow in vivo [8,9] or changes in diameter of isolated artery segments ex vivo in response to mechanical or pharmacological stimuli, such as ACh [10]. In humans, the gold-standard non-invasive assessment of NO-mediated EDD is brachial artery flow-mediated dilation (FMD), in which the change in brachial artery diameter in response to increases in blood flow is determined [10,11].…”

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“…After microvascular anastomosis, measuring arterial patency and flow velocity is crucial. Methods used include Doppler US (Figure g), CT angiography, MRI angiography, conventional angiography (Figure h), and optical coherence tomography. ,,, Measuring small vessels such as the femoral artery in rats and mice is technically difficult, particularly with Doppler US and arterial catheterization. ,,, In the literature, femoral artery flow velocities, patency, and artery diameters were examined in a few studies with radiologic imaging methods after microanastomosis in rats and generally evaluated in the early first week and the late sixth week. , …”

“… 7 , 16 , 23 , 86 Measuring small vessels such as the femoral artery in rats and mice is technically difficult, particularly with Doppler US and arterial catheterization. 62 , 63 , 86 , 87 In the literature, femoral artery flow velocities, patency, and artery diameters were examined in a few studies with radiologic imaging methods after microanastomosis in rats and generally evaluated in the early first week and the late sixth week. 17 , 27 …”

“…7,16,23,86 Measuring small vessels such as the femoral artery in rats and mice is technically difficult, particularly with Doppler US and arterial catheterization. 62,63,86,87 In the literature, femoral artery flow velocities, patency, and artery diameters were examined in a few studies with radiologic imaging methods after microanastomosis in rats and generally evaluated in the early first week and the late sixth week. 17,27 In our study, arterial patency was found to be 100% in both the control and gel groups at the sixth week and sixth month, while there was a vein thrombus at the sixth week and sixth month in the gel for vein groups.…”