B-Flow and B-Mode Ultrasound Imaging in Carotid Fibromuscular Dysplasia

Previous ultrasound studies in fibromuscular dysplasia (FMD) have largely reported on color flow imaging, power Doppler, and Doppler flow augmentation. We here report on arterial wall imaging findings by B-flow and B-mode in patients with carotid FMD.

We retrospectively reviewed ultrasonographic findings in subjects with known or suspected FMD. All patients were evaluated with a standardized imaging protocol including Doppler, B-mode, and B-flow. Vessel wall abnormalities were classified as normal, luminal irregularities, or classical beading (fusiform dilatations).

We identified 23 patients and 33 carotid arteries were found to be abnormal, of which 10 had classical beading and 23 showed endoluminal irregularities. Bilateral disease was present in 10/23 patients. In the classical beading cases, B-mode revealed isoechoic ridges, which protruded into the lumen, alternating with dilated arterial segments, which were also clearly demonstrated by B-flow imaging. In cases with endoluminal irregularities, B-mode and B-flow showed isoechoic subendothelial irregular thickening, which did not lead to a fusiform dilatory appearance of the artery. The average distal internal carotid artery peak systolic velocity of arteries with classical beading (123 ± 29 cm/second) was significantly greater than that of arteries with mild irregularities (94 ± 34 cm/second) (P = .024).

Morphological arterial wall changes of FMD were well depicted by careful B-flow and B-mode imaging of the distal internal carotid artery. We would like to emphasize the utility of B-flow and B-mode in the noninvasive evaluation of FMD.