Accurate Measurement of Carotid Stenosis

Abstract

The methods used for measurement of carotid artery stenosis are not uniform. Witness the chaos that developed when the North American Symptomatic Carotid Endarterectomy Trial (NASCET) group changed its classification system from area to linear measurements only to discover that the European Carotid Stenosis Trial (ECST) used still another angiographic definition of degree of stenosis so that the data from the two studies were not comparable. Fortunately, this has been reconciled by recalculation of the data. In still other studies, using unvalidated ultrasound instruments has made it difficult or impossible to compare results. In part, these problems have been the result of misdirected attempts to amalgamate concepts from Doppler and duplex ultrasound with those of arteriography. The former is more precise and accurate than the latter, yet its methodology is harder to apply and has not been generally distributed. Even such anatomical terms as "carotid bulb" are not standard. Ultrasonographers consider it to be the distal common carotid artery, to vascular surgeons it is the carotid sinus, while still others consider it to be both or neither. The present authors advocate a uniform methodology utilizing duplex ultrasound and predict that it plus magnetic resonance angiography will become the standard by which extracranial carotid artery disease is evaluated in the future.

Asymptomatic Carotid Artery Stenosis Treated with Medical Therapy Alone: Temporal Trends and Implications for Risk Assessment and the Design of Future Studies

“…The lack of difference may be due to heterogeneity in the definition and measurement of the degree of stenosis across studies [31]. When analyses were stratified by stenosis severity (instead of using meta-regression), the difference became more pronounced (2.4 vs. 1.6 per 100 person-years).…”

Guidelines for Carotid Endarterectomy

“…Although direct comparisons among studies are not possible due to differences in inclusion and exclusion criteria, end points, and methods of determining severity of carotid stenosis, analysis of these three trials has shown that carotid endarterectomy is of benefit in symptomatic patients with severe carotid occlusive disease. [56][57][58][59][60] The ECST 61,62 was a randomized, controlled trial using transient cerebral ischemia, nondisabling stroke, transient monocular blindness, or retinal infarction as qualifying symptoms for entry if both the treating surgeon and neurologist were "substantially uncertain" about whether or not to recommend surgery. Eighty European centers contributed 455 surgical and 323 medical patients with 70% to 99% stenosis who were followed for a mean duration of 2.7 years.…”

Three-Dimensional Computed Tomography Angiography and Magnetic Resonance Angiography of Carotid Bifurcation Stenosis

“…Duplex-Doppler sonography (DS) of the carotid arteries is the most widely accepted noninvasive screening method. However, because of some imaging pitfalls and because it depends on the skills of the operator, ultrasound is not considered as a gold standard method and alone cannot replace an intra-arterial angiography [13, 14]. MRA can evaluate vascular disease by directly depicting the carotid arteries without the use of contrast agents; it allows complete vascular examination of extracranial and intracranial arteries.…”