Unilateral Carotid Artery Disease Research Articles

Mapping Cerebrovascular Reactivity Impairment in Patients With Symptomatic Unilateral Carotid Artery Disease.

BackgroundComprehensive hemodynamic impairment mapping using blood oxygenation‐level dependent (BOLD) cerebrovascular reactivity (CVR) can be used to identify hemodynamically relevant symptomatic unilateral carotid artery disease.Methods and ResultsThis prospective cohort study was conducted between February 2015 and July 2020 at the Clinical Neuroscience Center of the University Hospital Zurich, Zurich, Switzerland. One hundred two patients with newly diagnosed symptomatic unilateral internal carotid artery (ICA) occlusion or with 70% to 99% ICA stenosis were included. An age‐matched healthy cohort of 12 subjects underwent an identical BOLD functional magnetic resonance imaging examination. Using BOLD functional magnetic resonance imaging with a standardized CO2 stimulus, CVR impairment was evaluated. Moreover, embolic versus hemodynamic ischemic patterns were evaluated on diffusion‐weighted imaging. Sixty‐seven patients had unilateral ICA occlusion and 35 patients unilateral 70% to 99% ICA stenosis. Patients with ICA occlusion exhibited lower whole‐brain and ipsilateral hemisphere mean BOLD‐CVR values as compared with healthy subjects (0.12±0.08 versus 0.19±0.04, P=0.004 and 0.09±0.09 versus 0.18±0.04, P<0.001) and ICA stenosis cohort (0.12±0.08 versus 0.16±0.05, P=0.01 and 0.09±0.09 versus 0.15±0.05, P=0.01); however, only 40 (58%) patients of the cohort showed significant BOLD‐CVR impairment. Conversely, there was no difference in mean BOLD‐CVR values between healthy patients and patients with ICA stenosis, although 5 (14%) patients with ICA stenosis showed a significant BOLD‐CVR impairment. No significant BOLD‐CVR difference was discernible between patients with hemodynamic ischemic infarcts versus those with embolic infarct distribution (0.11±0.08 versus 0.13±0.06, P=0.12).ConclusionsComprehensive BOLD‐CVR mapping allows for identification of hemodynamically relevant symptomatic unilateral carotid artery stenosis or occlusion.

The Role of Intraindividual Carotid Artery Variation in the Development of Atherosclerotic Carotid Artery Disease: A Literature Review

Carotid artery disease (CAD) is associated with numerous risk factors, including hypertension, hyperlipidemia, hypercholesterolemia, diabetes mellitus, and smoking. These systemic risk factors do not affect the carotid arteries equally in most patients, resulting in asymmetrical bilateral and unilateral CAD. It is unclear if anatomic variations in the carotid arteries predispose an individual to formation of atherosclerotic CAD. We wanted to assess (1) the inter-individual or intra-individual anatomical variations in the carotid arteries and (2) whether anatomical variations predispose the development of atherosclerotic CAD. PubMed and Medline were utilized to identify relevant literature for critical appraisal, summarization and documentation. Inclusion and exclusion criteria were applied to narrow results and articles were critically appraised and analyzed. Evidence suggests that a low outflow/inflow ratio, elevated bifurcation height, and bifurcation angle are associated with increased risk for CAD. Sex and age demonstrated positive correlation with the disease. Additionally, tortuosity and kinking of the carotid arteries may affect the formation of CAD but coiling of the arteries is a natural age-dependent process and does not affect CAD development. This review suggests there are anatomic variations in the carotid arteries that increase the risk of developing carotid artery disease. The most significant risk factors include a low outflow/inflow ratio, increased internal carotid artery tortuosity, elevated bifurcation height, and bifurcation angle.

Evaluation of cerebrovascular reserve in patients undergoing carotid artery stenting and its usefulness in predicting significant hemodynamic changes during temporary carotid occlusion.

We investigated the usefulness of cerebrovascular reserve (CVR) testing to predict severe hemodynamic changes during proximally protected carotid artery stenting. Of 90 patients referred, 63 eligible underwent complete evaluation of the extent of carotid artery disease and transcranial Doppler ultrasound (TCD) assessment of CVR by means of a breath-holding test and ophthalmic artery flow pattern evaluation. Periprocedural TCD monitoring of the ipsilateral middle cerebral artery flow was performed in 24 patients undergoing proximally protected procedure (requiring induction of flow arrest within internal carotid artery). Abnormal CVR was significantly less common in patients with unilateral compared to bilateral carotid artery disease (26.3 % vs. 76.9 %, p=0.02), while ophthalmic artery flow reversal was rare in patients with unilateral carotid artery disease (2.5 % vs. 42.9 %, p<0.01). During the induction of carotid flow arrest, the average mean flow velocity drop following external carotid artery occlusion was low (3.5 %, p=0.67) compared to the induction of complete flow arrest (32.8 %, p<0.01). Six patients had a total mean flow velocity drop >50 %, including 2 patients with normal pre-procedural CVR. Our results suggest that TCD evaluation of CVR is not a reliable predictor of hemodynamic changes induced during proximally protected carotid artery stenting in patients with unilateral carotid artery disease.

Hand gripping and acetazolamide effect in normal persons and patients with carotid artery disease.

Transcranial Doppler measurement (TCD) of cerebrovascular reserve (CVR) is usually performed by the CO2 test, the acetazolamide test, or the breath-holding test. Since these tests are time-consuming and labor-intensive, alternative methods such as the hand-gripping test are of interest. Twenty-one normal persons and 25 patients with unilateral carotid artery disease were studied. Flow velocity changes in both middle cerebral arteries (MCAs) during bilateral hand gripping were measured by TCD and compared with acetazolamide test results. The increase in MCA mean flow velocity (FVmean) during hand gripping was 18.0 +/- 6.3% in normal persons; the increases in the post-stenotic MCA were 15.8 +/- 9.7% in all patients and 9.4 +/- 5.4% in patients with impaired CVR as determined by the acetazolamide test. Only in the group with impaired acetazolamide reactivity was the increase in the poststenotic MCA significantly lower compared to that in controls (p < 0.01) and to the contralateral, nonstenotic side (p < 0.01). Nevertheless the FVmean increases in both tests showed a weak, but significant correlation (r = 0.59, p < 0.01). All FVmean increases during hand gripping were significantly (p < 0.01) lower than those during the acetazolamide test. The test appears as a weaker stimulus for MCA blood flow velocity increase than the acetazolamide test. Thus, only a substantial reduction of acetazolamide reactivity leads to a reduced MCA FVmean increase using hand gripping. Although it is highly specific but less sensitive, hand gripping does not appear to be suitable as a screening measure of CVR, but might be useful in addition to standard tests.

Aqueous Humor Flow in Unilateral Carotid Stenosis

Our purpose was to study the relationship between carotid artery occlusive disease and aqueous flow in human subjects. Aqueous humor flow was measured by fluorophotometry in seven patients with unilateral carotid artery disease documented by oculoplethysmography. The mean (+/- SD) flow was 2.03 +/- 0.38 microliter/min in the affected eyes, 2.44 +/- 0.66 microliter/min in the unaffected contralateral eyes, and 2.56 +/- 0.61 microliter/min in a group of 14 age-matched controls. A statistically significant difference (p < 0.05) in the aqueous flow rate was seen between the affected and unaffected eyes and between the affected and control eyes. Aqueous flow in the unaffected and control eyes was not statistically different. The anterior chamber volumes and intraocular pressures were also not significantly different among groups. Severe carotid artery disease may reduce aqueous humor formation by lowering ciliary body blood flow to a point beyond which the eye cannot compensate.

Cerebral vasoreactivity in unilateral carotid artery disease. A comparison of blood flow velocity and regional cerebral blood flow measurements.

Hemodynamic information obtained by assessing cerebral vasoreactivity is of clinical interest and may have prognostic significance in patients with occlusive carotid disease. The aim of this study was to compare the results of transcranial Doppler and regional cerebral blood flow studies when used to assess cerebral vasoreactivity. Blood flow velocities in both middle cerebral arteries and regional cerebral blood flow in their respective perfusion territories were compared in 52 patients with severe unilateral carotid stenosis or occlusion. The studies were first performed under basal conditions and repeated after the intravenous administration of 1 g acetazolamide. Asymmetry (normal compared with pathological side) in middle cerebral artery blood velocity increase was significantly greater than the asymmetry in cerebral blood flow increase in the perfusion territories of the arteries. A significant correlation (r = .63, P < .0001) was found between asymmetry in percent velocity increase and asymmetry in absolute cerebral blood flow increase. The two methods agreed in their assessment of either a normal or a reduced vasoreactivity in 38 subjects and disagreed in 14. In six of the latter patients, who had no evidence of cerebral infarction, the asymmetry in velocity increase was abnormal, whereas asymmetry in flow increase was assessed as normal. We found a good correlation between the asymmetry in regional cerebral blood flow increase in the middle cerebral artery perfusion territories and asymmetry in the velocity increase in the middle cerebral arteries after administration of acetazolamide. These results suggest that transcranial Doppler examination combined with the acetazolamide test may be used in clinical situations to assess cerebral vasoreactivity.

Cerebrovascular reactivity to acetazolamide in carotid artery disease. Enhancement of side-to-side CBF asymmetry indicates critically reduced perfusion pressure.

Cerebral blood flow (CBF), measured with a mobile 10 detector unit and non-invasive Xenon-133 technique, was investigated before and after cerebral vasodilation with acetazolamide (Diamox) in 78 patients prior to carotid endarterectomy. The change in side-to-side CBF asymmetry from baseline to Diamox study, the Diamox asymmetry enhancement, was compared with the intraoperatively measured cerebral perfusion pressures. Asymmetry enhancement exceeded the methodological variation in 14 patients, 13 of whom had a perfusion pressure below 65 mmHg. Insignificant asymmetry enhancement was found in 64 patients: 52 with unilateral and 12 with bilateral disease. Of these two and four patients, respectively, had perfusion pressures below 65 mmHg. Enhancement of CBF asymmetry following a potent cerebral vasodilator stimulus is a reliable predictor, in unilateral carotid artery disease, of critically reduced cerebral perfusion pressure.