Intracranial Flow Volume Estimation in Patients with Internal Carotid Artery Occlusion

Abstract

(1) Background: Carotid artery occlusion (CAO) in population studies has a reported prevalence of about 6 per 100,000 people; however, the data may be underestimated. CAO carries a significant risk of stroke. Up to 15% of large artery infractions may be secondary to the CAO, and in 27−38% of patients, ischaemic stroke is a first presentation of the disease. The presence of sufficient and well-developed collateral circulation has a protective influence, being a good prognostic factor in patients with carotid artery disease, both chronic and acute. Understanding the mechanisms and role of collateral circulation may be very important in the risk stratification of such patients. (2) Materials and Methods: This study included 46 patients (mean age: 70.5 ± 6 years old; 15 female, mean age 68.5 ± 3.8 years old and 31 male, mean age 71.5 ± 6.7 years old) with unilateral or bilateral ICA occlusion. In all patients, a Doppler ultrasound (DUS) examination, measuring blood flow volume in the internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA), was performed. The cerebral blood flow (CBF) was compared to the previously reported CBF values in the healthy population >65 years old. (3) Results: In comparison with CBF values in the healthy population, three subgroups with CBF changes were identified among patients with ICA occlusion: patients with significant volumetric flow compensation (CBF higher than average + standard deviation for healthy population of the same age), patients with flow similar to the healthy population (average ± standard deviation), and patients without compensation (CBF lower than the average-standard deviation for healthy population). The percentage of patients with significant volumetric flow compensation tend to rise with increasing age, while a simultaneous decline was observed in the group without compensation. The percentage of patients with flow similar to the healthy population remained relatively unchanged. ICA played the most important role in volumetric flow compensation in patients with CAO; however, the relative increase in flow in the ICA was smaller than that in the ECA and VA. Compensatory increased flow was observed in about 50% of all patent extracranial arteries and was more frequently observed in ipsilateral vessels than in contralateral ones, in both the ECA and the VA. In patients with CAO, there was no decrease in CBF, ICA, ECA, and VA flow volume with increasing age. (4) Conclusions: Volumetric flow compensation may play an important predictive role in patients with CAO.

Keywords: Doppler ultrasonography; carotid artery disease; carotid occlusion; cerebral blood flow; cerebrovascular reserve.

Figure 1

Tendencies in CBF changes in different age groups. The percentage of patients with significant flow compensation tends to rise with increasing age. The opposite trend is observed in the group with decreased flow volume. The age 75–79 group was excluded from the analysis.

Figure 2

Changes in the relative level of compensation in extracranial arteries in patients with ICA occlusion. The relative level of compensation rises in ICA and VA with increasing age, while in ECA it remains almost unchanged.

Figure 3

The percentage of patent arteries with and without flow compensation. The compensatory increased flow volume was most frequently observed in the contralateral ICA—54.76%, in 48.91% of ECAs, and in the 51.09% of VAs.

Figure 4

Differences in compensation between ipsilateral and contralateral vessels. Compensatory increased flow was more frequently observed in ipsilateral vessels (23 vs. 16—ECA) and 22 vs. 17—VA).

Figure 5

Scatter plot of the volumetric flow compensation in ICA and age (y = 316.0092 + 1.33778x). No correlation was observed (p = 0.64).

Figure 6

Scatter plot of the volumetric flow compensation in ECA and age (y = 325.7611 − 1.45048*x). No correlation was observed (p = 0.52).

Figure 7

Scatter plot of the volumetric flow compensation in VA and age (y = 293.8499 − 1.4929*x). No correlation was observed (p = 0.42).

Figure 8

Scatter plot of cerebral blood flow volume and age (y = 1031.6346—1.8803*x). No correlation was observed (p = 0.71).

Figure 9

The number of female and male participants in our study group.

Figure 10

Compensation in patient with bilateral ICA occlusion. (A) Right-sided ICA occlusion; (B) left-sided ICA occlusion; (C) compensatory increased flow in RECA with flow volume of 230 mL/min; (D) flow volume in LECA of 86 mL/min; (E) compensatory increased flow in RVA with flow volume of 285 mL/min; (F) compensatory increased flow in LVA with flow volume of 302 mL/min. Flow was within the reference values despite bilateral CAO.

Figure 11

Patient with left-sided ICA occlusion, 70% right-sided ICA stenosis, and no significant flow compensation in other extracranial arteries. (A,B) About 70% RICA stenosis with flow velocity of 2.97/0.83 m/s; (C) distal part of the ICA with flow volume of 275 mL/min; (D) flow volume in RECA of 84 mL/min—no compensation; (E) flow volume in RVA of 59 mL/min—no compensation; (F) left-sided LICA occlusion; (G) slightly compensatory increased flow in LECA with flow volume of 153 mL/min; (H) flow volume in LVA of 65 mL/min—no compensation. Due to the lack of volumetric flow compensation, early elective surgical treatment should be considered.