Carotid near-occlusion can be identified with ultrasound by low flow velocity distal to the stenosis

Abstract

Background Most carotid near-occlusions are indistinguishable from conventional ≥ 50% stenosis on ultrasound, demonstrating high peak systolic velocity (PSV) in the stenosis. Purpose To study whether the velocity distal to the stenosis can separate high PSV near-occlusion from conventional ≥ 50% stenosis. Material and Methods We included patients with ≥ 50% carotid stenosis with high PSV (≥125 cm/s), examined with both computed tomography angiography (CTA) and ultrasound within 30 days, and a distal velocity measurement was performed. Based on CTA, cases were divided into three groups: conventional stenosis; near-occlusion without full collapse (NwoC; normal-appearing albeit small distal artery); and near-occlusion with full collapse (NwC; threadlike distal artery). Distal Doppler ultrasound flow velocities were compared between these groups. Results Sixty patients were included: 33 patients with conventional stenosis; 20 patients with NwoC; and seven patients with NwC. Mean distal PSV was 93, 63, and 21 cm/s ( P < 0.001) and mean distal end-diastolic velocity was 30, 24, and 5 cm/s ( P < 0.001), respectively. A distal PSV < 50 cm/s was 63% sensitive and 94% specific for separating both types of near-occlusion from conventional stenosis. Conclusion In high PSV carotid stenoses, the distal velocity was lower in near-occlusions than conventional carotid stenosis. Distal velocities warrant further investigation in diagnostic studies.

Near-occlusion is difficult to diagnose with common carotid ultrasound methods

“…Furthermore, suspected near-occlusions were not pre-specified categories, hence not systematically used in our entire cohort, some with similar findings might have been missed. All these findings have been reported previously [6,9,18], and additional types of unusual findings might be possible. Distal artery size was not systematically assessed, in large part due to the lack of diagnostic threshold for such a measurement [7,8].…”

“…Therefore, it is reasonable to suspect that assessment of distal artery size on ultrasound might not be very sensitive for near-occlusion. After this cohort was examined, low velocity distal to the stenosis has emerged as a possible new method specific for near-occlusion [18], i.e., not indicative for severe conventional stenosis as indicated in a guideline [6]. Also, ultrasound contrast might improve separation of occlusion and nearocclusion [19].…”

Diagnosing Carotid Near-Occlusion with Phase-Contrast MRI

“…See the Online Supplemental Data for details on PC MR imaging literature. The association between near-occlusion and flow might also improve understanding of prognostics 4,14 and sonography findings 8,15 in near-occlusion. Other PC MR imaging techniques (2D and 3D) are likely to produce similar results, but they should be evaluated.…”

Defining carotid near-occlusion with full collapse: a pooled analysis

“…Although our definitions make separation against full collapse easy, a diagnostic challenge remains for separation from conventional stenosis [13,16]. Further diagnostic work is warranted, which can include both ultrasound and phase contrast approaches [18,19].…”