Volumetric Flow Assessment in Doppler Ultrasonography in Risk Stratification of Patients with Internal Carotid Stenosis and Occlusion

Abstract

(1) Background: Alterations of blood flow volume in extracranial arteries may be related to the risk of occurrence of neurological symptoms. The aim of this study was the estimation of cerebral blood flow (CBF) in Doppler ultrasonography, as well as comparison of the flow volume in asymptomatic patients over 65 years old with ≥50%, and symptomatic patients with ≥70% internal carotid artery (ICA) stenosis, in order to assess whether the changes in the CBF correlates with the presence of neurological symptoms. (2) Methods: 308 patients over 65 years old were included in the retrospective cohort observational study: 154 asymptomatic with ≥50% ICA stenosis, 123 healthy volunteers, and 31 symptomatic referred for surgical treatment. The study group was split according to ICA stenosis (50–69%, 70–99% and occlusion). In all patients an extensive Doppler ultrasound examination with measurements of flow volume in common, internal, external carotid (ECA) and vertebral arteries (VA) was performed. (3) Results: Among asymptomatic (A) and symptomatic (S) patients with carotid stenosis 3 subgroups were identified: 57/154—37% (A) and 8/31—25.5% (S)—with significantly increased flow volume (CBF higher than reference range: average CBF + std. dev in the group of healthy volunteers), 67/154—43.5% (A) and 12/31—39% (S)—with similar to reference group flow volume (CBF within range average ± std.dev), and 30/154—19.5% (A) and 11/31—35.5% (S)—with decreased flow volume in extracranial arteries (flow lower than average-std.dev. in healthy volunteers). In symptomatic patients the percentage of patients with significant compensatory increased flow tends to raise with the severity of the stenosis, while simultaneous decline of number of patients with mild compensation (unchanged total CBF) is observed. The percentage of patients without compensation remains unchanged. In the group referred for surgical treatment (symptomatic, ≥70% ICA stenosis) the percentage of patients with flow compensation is twice as low as in the asymptomatic ones with similar degree of the ICA stenosis (8/31—25.8% vs. 26/53—49%, p = 0.04). Compensatory elevated flow was observed most frequently in ECA. (4) Conclusions: The presence of significant volumetric flow compensation has protective influence on developing ischaemic symptoms, including TIA or stroke. The assessment of cerebral inflow in Doppler ultrasonography may provide novel and easily accessible tool of identifying patients prone to cerebral ischaemia. The multivessel character of compensation with enhanced role of ECA justifies the importance of including this artery in the estimation of CBF.

Volumetric Flow Assessment in Extracranial Arteries in Patients with 70–99% Internal Carotid Artery Stenosis

“…The significant compensatory elevation of CBF is more frequently observed in asymptomatic patients suffering from severe ICA stenosis, which suggests its protective influence on developing ischaemic symptoms. The relative risk of observing the compensatory increased flow in extracranial arteries in asymptomatic patients is almost two times higher than in symptomatic ones [ 9 , 12 ].…”

“…During the preliminary research our team identified a cut-off point in almost exactly one sigma from the mean. Not only did it allow us to identify the differences between asymptomatic and symptomatic patients but it also permitted a prediction of the postoperative increase in CBF in patients who undergo surgical treatment due to ICA stenosis [ 12 , 41 ]. Narrowing the confidence interval is acceptable when there are justified indications.…”

“…The stenosis degree assessment was based on the Results of Society of Radiologists in Ultrasound Consensus Conference on the diagnosis of Internal Carotid Artery Stenosis and DEGUM criteria—using the peak systolic velocity (PSV), end-diastolic velocity (EDV) changes as well as ICA PSV/CCA PSV ratio, post-stenotic flow disturbances (severity and length), and reduction. Additional criteria were used for ICA stenoses that exceeded 80%: prolongation of acceleration time >0.4 s and flow velocity reduction in the upper portion of the vessel and the PSV ratio between the stenosis and the upper part over 8.0 [ 9 , 12 , 15 , 16 , 17 ].…”

“…There are also patients in whom the CBF is similar to healthy population—due to the mild increase in the flow in other extracranial vessels, and the patients in whom there is no flow increase in other arteries—those patients have lower CBF values than the healthy population. It was reported that higher CBF values are correlated with a lower risk of occurrence of ischaemic symptoms, while in patients with lower CBF values the risk of occurrence of ischaemic symptoms is twice as large [ 9 , 10 , 11 , 12 , 13 , 14 ].…”

Characteristics of non-stenotic carotid plaque in embolic stroke of undetermined source compared with cardiogenic embolism: a retrospective cross-sectional observational study

“…In a study that used multimodal ultrasound to investigate plaque risk stratification in patients with asymptomatic carotid stenosis, plaque surface morphology, intraplaque neovascularization grades, and carotid stenosis degree were found to be risk factors for ischemic vascular events [ 22 ]. Also, a study using doppler ultrasonography to assess global cerebral inflow discovered that individuals with decreased cerebral blood flow were more likely to develop ischemia, providing a novel and simple way for detecting patients at risk of cerebral ischemia [ 23 ]. However, ultrasound is used primarily in assessing the echogenicity of plaques and has lower sensitivity for detecting plaque ulceration when compared to CT and MR angiography [ 6 ].…”