Vascular Medicine. Thomas Zeller

target="_blank" rel="nofollow" href="#fb3_img_img_6490c939-e834-5df3-98e5-854c43951ec0.jpg" alt=""/> In addition to the hypoechoic occlusion, evidence of prior arteriosclerosis with sonographically complex plaques and structures creating acoustic shadows, possibly “older” echogenic occlusion components

      

Involvement particularly of proximal vascular segments and vascular segments near the aortic arch and of branches of the external carotid artery (superficial temporal artery)

      Dissection:

      

There may initially be a floating dissection membrane.

      

The true lumen may be alternately compromised as far as the occlusion—possibly with a sharply tapering occlusion pattern (the string sign).

      

The false lumen may thrombose.

      

When there is a floating membrane, there may be a pathognomonic triphasic “splash signal.”

      

Circumscribed mural hematomas may occur (“carotidynia”).

      

Variants:

      – The vertebral artery in particular often shows hypoplasia and also aplasia.

      – Definition of vertebral artery hypoplasia: vascular diameter < 2.5 mm or diameter ratio > 1:1.7.

      

Large-vessel vasculitis:

      – Typical homogeneous, hypoechoic and widened intima–media complex (macaroni sign)

      

Caution: there are often respiratory-modulated buckling stenoses in the subclavian artery, particularly on the left side, which regress on inspiration.

      Table 1.1–1 The reaction pattern in the supratrochlear artery during compression of the external branches.

Increased flow	Evidence of normal orthograde flow
Reverse flow	Evidence of pathological retrograde flow
Reduced flow	Evidence of pathological retrograde flow; intracranial perfusion pressure probably poorer than with reverse flow
No reaction	If there are no notable external–internal carotid artery anastomoses or maxillary/ethmoidal artery collaterals → contralateral compression, and then alternatively a compression test in the supraorbital region → an increase in outflow resistance leads to reduced flow velocities, particularly diastolic → pulsatility increases
Zero flow, with evidence of flow only during compression	Pathological → equalized extracranial/intracranial pressure

      Fig. 1.1–4 Carotidynia: hypoechoic focal wall thickening, representing mural hematoma.

      

      Specific findings

       Common carotid artery

      The width of the boundary zone reflection (synonymous with the intima–media thickness, IMT) in the common carotid artery (CCA, and other vessels) has been found to be a parameter for assessing the atherosclerotic risk, and it correlates with the incidence of vascular events.

      Fig. 1.1–5a, b Dissection of the internal carotid artery. (a) A visible dissection membrane in the area of the common carotid artery. (b) The typically altered polyphasic pulsed-wave Doppler signal.

      There is no established classification based on maximum velocities for grades of stenosis in common carotid artery stenoses. In addition to the general characteristics of a stenosis (see under internal carotid artery stenoses), the peak velocity ratio (PVR) can be used.

      Internal carotid artery

      Various angiographic grading methods are available, with differing percentage figures. The residual diameter may refer either to the distal diameter of the internal carotid artery, with the local stenosis grade based on the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria; or to the original proximal diameter, with the local stenosis grade based on the European Carotid Surgery Trial (ECST) criteria. An approximate formal conversion can be carried out:

      Local stenosis grade (based on ECST): ECST % = 0.6 × NASCET % + 40%

       Distal stenosis grade (based on NASCET): NASCET % = (ECST – 40%)/0.6

      The traditional duplex ultrasound criteria used by the German Society for Ultrasound in Medicine (Deutsche Gesellschaft für Ultraschall in der Medizin, DEGUM) correlated with the ECST local stenosis grade (although the NASCET method was mainly used in radiography). The DEGUM criteria were revised in 2010 to establish comparability and transferred to NASCET (Table 1.1-3). The method used for duplex ultrasound classification must be clearly stated.

      N.B.: Confusion may arise when the old and new stenosis grades for the internal carotid artery are compared or used in parallel. Stenoses in other locations (external carotid artery, vertebral artery, common carotid artery, etc.) are generally continuing to be classified according to the local stenosis grade on the basis of previously customary hemodynamic criteria. Supra-aortic stenoses with the same local stenosis grade in other vascular territories may therefore be given as “higher” percentages than internal carotid artery stenoses, which are classified according to the distal stenosis grade.

      Fig. 1.1–6 NASCET–ECST: the principles of stenosis grading based on NASCET and ECST (B flow imaging).

      Table 1.1–2 Age-dependent and gender-dependent normal values for intima–media thickness (IMT) in the common carotid artery (CCA), showing means, standard deviations, and 95% confidence intervals (Temelkova-Kurktschiev et al. 2001).

      In addition to hemodynamic criteria, new B-image optimization techniques and digital subtraction ultrasonography (B flow) provide effective assistance in demonstrating the morphology. Bifurcation stenoses in particular are often missed or incorrectly classified in angiographic procedures.

      Cross-sectional planimetry correlates more with the local stenosis grade and is associated with error due to vascular remodeling of the internal carotid artery. A compensatory increase in the terminal diameter of the vessel occurs with increasing grades of stenosis, so that the percentage grade of stenosis is incorrectly raised. These values therefore need to be treated with caution.

      Fig. 1.1–7a, b Bifurcation stenosis of the internal carotid artery. (a) Imaging of a high-grade, eccentric internal carotid artery stenosis with apparently