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

Abstract

Purpose To assess the sensitivity and specificity of common carotid ultrasound method for carotid near-occlusion diagnosis. Methods Five hundred forty-eight patients examined with both ultrasound and CTA within 30 days of each other were analyzed. CTA graded by near-occlusion experts was used as reference standard. Low flow velocity, unusual findings, and commonly used flow velocity parameters were analyzed. Results One hundred three near-occlusions, 272 conventional ≥50% stenosis, 162 <50% stenosis, and 11 occlusions were included. Carotid ultrasound was 22% (95%CI 14–30%; 23/103) sensitive and 99% (95%CI 99–100%; 442/445) specific for near-occlusion diagnosis. Near-occlusions overlooked on ultrasound were found misdiagnosed as occlusions (n = 13, 13%), conventional ≥50% stenosis (n = 65, 63%) and < 50% stenosis (n = 2, 2%). No velocity parameter or combination of parameters could identify the 65 near-occlusions mistaken for conventional ≥50% stenoses with >75% sensitivity and specificity. Conclusion Near-occlusion is difficult to diagnose with commonly used carotid ultrasound methods. Improved carotid ultrasound methods are needed if ultrasound is to retain its position as sole preoperative modality.

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

“…In this analysis, only those that were examined with computed tomography angiography (CTA) of sufficient quality within 6 months of the presenting event were included. Ultrasound, which was otherwise used alone, has poor sensitivity for near-occlusion [ 10 , 11 ]. A total of 430 patients with symptomatic ≥ 50% carotid stenosis were included of which 116 (27%) had near-occlusion, 47 with and 69 without full collapse.…”

Diagnosing carotid near-occlusion is a difficult task—but it might get easier

“…Feature interpretation is arguably the current reference method as it was used to diagnose near-occlusion in the major RCTs [9] and in relevant prognostic studies [6], albeit Manrique-Zegarra did not use this approach [1]. Feature interpretation is performed by assessing various available features to determine if the distal ICA is small and if more proximal stenosis is the cause of the distal ICA collapse.…”

“…Also, approximately 5% of cases with ≥ 50% have such divergent features that the cause of small distal ICA was unclear [10]. Such cases have been presumed to be conventional stenosis in prognostic studies [6,9]. Some of these were the near-occlusion entity, some not, but no current method can tell the difference.…”

“…Whether near-occlusion with full collapse (Fig. 2) should be identified and treated separately from without full collapse is debatable [6][7][8]. In this editorial, we will put these findings in a larger perspective, highlighting difficulties in image assessments and diameter measurements, and present a possible solution for future studies: postoperative angiography as a new reference test.…”

“…Our suggestion is to move closer to the near-occlusion entity, beyond feature interpretation, when creating new diagnostic criteria. However, it is unclear if the low risk of recurrent stroke known from studies using feature interpretation will be applicable to all near-occlusion entity cases [6,9]. The mechanism explaining why near-occlusion protects from future stroke compared to having conventional stenosis is not well established [2].…”