Reduced flow velocity in the internal carotid artery independently of cardiac hemodynamics in patients with cerebral ischemia

Anatomical characteristics and morphometric analyses of the internal carotid artery using retrospective angiographic images

PURPOSE

Anatomical variations of the internal carotid artery (ICA) can cause complications during endovascular treatments. Therefore, the aim of this study was to investigate the features of the ICAs obtained from 2D digital subtraction angiography (2D DSA).

METHODS

The morphometrics and angles of the ICA segments from 2D DSA images from a total of 100 patients (45 males and 55 females) were investigated. The lengths (L1-3), angles (A1-3), and diameters (D1-6) through the ICA measurement points (five segments: C2 [petrous], C3 [lacerum], C4 [cavernous], C5 [clinoid], C6 [ophthalmic]) were systemically recorded by two observers. All measured parameters were compared for both sexes and sides.

RESULTS

The lengths (mm) and angles of the ICA were 7.20 ± 2.22 (L1), 15.71 ± 2.32 (L2), 10.99 ± 1.66 (L3) and 109.31 ± 17.77 (A1), 107.87 ± 20.51 (A2), 80.81 ± 16.33 (A3), respectively. There were no differences in the angulations of the A1-A3 segments between the sexes (p > 0.05). The L2 (C3-C4) was significantly longer in males, but only the left side of females showed a greater length (p < 0.05). The averaged mean diameters of the ICA (D1-6) in both sexes were 4.17 ± 0.55 mm. However, the diameters of the D1-D6 from left and right sides of males except the right D6 were significantly longer than those of females (p < 0.05). Also of significance was that the right diameters of females (D1) and males (D1 and D2) were shorter compared to left sides.

CONCLUSION

This study demonstrates some differences in lengths, diameters, and angles in both sexes and sides of the normal ICA. Neurosurgeons and neurointerventionalists should be aware of such variations when operating, performing interventional procedures, and interpreting 2D DSA.

Associations of Blood Pressure and Carotid Flow Velocity with Brain Volume and Cerebral Small Vessel Disease in a Community-Based Population

Cerebral small vessel disease (CSVD) is a common finding on brain magnetic resonance imaging (MRI). We previously demonstrated that high blood pressure (BP) and low carotid flow velocity were associated with cerebrovascular disease. However, their associations with brain volume and CSVD remain to be determined. A total of 721 adults (≥ 50 years) from the community-based I-Lan Longitudinal Aging Study were included. Flow velocities at the common (CCA) and internal carotid artery (ICA), including peak systolic velocity (PSV) and end-diastolic velocity (EDV), were measured with Doppler ultrasound. We further detected the presence of CSVD including lacune, microbleed, and white matter hyperintensity (WMH) on brain MRI, which were used to construct a combined CSVD score. General linear regression and logistic regression analysis were exploited to evaluate the association between carotid flow velocity, BP, brain volume, and CSVD. The mean of white matter, gray matter, and WMH volume were 422.2 cm³, 546.9 cm³, and 2.61 cm³, respectively. The proportion of lacune and microbleed were 11.1% and 14.2%, respectively. The CSVD score were negatively associated with gray (r = - 0.121, p < .01) and white matter volume (r = 0.058, p = 0.12), but positively associated with systolic BP (beta = 1.02, p = 0.0017). EDV at common carotid artery associated positively with white matter volume (beta = 1.013, p = 0.0064) and negatively predicted the presence CSVD (odds ratio [OR] = 0.93, p = 0.0023). In the ordinal logistic regression analysis adjusting for age, sex, total intracranial volume education, low-density lipoprotein cholesterol, and fasting glucose, compared with hypertensive subjects with low EDV, normotensive subjects with low, middle, and high EDV had an odds ratio of 0.656 (0.327-1.318), 0.429 (0.261-0.705), and 0.272 (0.147-0.502) for CSVD score, respectively. High SBP and low carotid flow velocities were independently associated with brain volume and CSVD. These associations may be involved in the pathophysiology of cognitive function decline.

Effects of continuous-flow left ventricular assist devices on cerebral hemodynamics

Continuous-flow left ventricular assist devices (LVADs) reduce peak systolic flow, increase diastolic flow, and eliminate pulsatility of circulation. Altered blood flow may lead to a change in end-organ perfusion. Analysis of the flow dynamics of the arteries of end organs, such as the brain, may indicate whether an organ is perfused sufficiently. The aim of this study is to evaluate and identify the flow pattern changes of carotid (CA) and middle cerebral arteries (MCA) in LVAD patients and to compare with heart failure patients and healthy volunteers. Eighty-nine individuals were included in this cross-sectional study. Participants were divided into three groups: LVAD patients (n = 31), heart failure patients (n = 26), and healthy volunteers (n = 27). Carotid and transcranial Doppler ultrasonography were performed for all study groups for peak systolic velocity (PSV), end-diastolic velocity (EDV), pulsatility (PI), and resistive (RI) indices of CA and MCA. Flow dynamics were compared between the groups. Doppler ultrasonographic data were analyzed at a median 12 (3-47) months after LVAD implantation. CA-PSV was lower in LVAD group compared with the other two groups (P < .001), MCA-PSV of LVAD and heart failure groups were similar and lower than healthy volunteers (P < .05). The highest values for CA-EDV were found in the LVAD group (P < .05). MCA-EDV values were found to be lowest in heart failure group (P < .05). For PI and RI, in all CA and MCA, the LVAD group had lower indices compared with the other two groups (P < .001). In addition, MCA flow analysis in patients with LVADs was identified for the first time with this study.

Hypercapnia-induced shear-mediated dilation in the internal carotid artery is blunted in healthy older adults

This study aimed to elucidate the effect of aging on shear-mediated dilation of the common and internal carotid arteries (CCA and ICA, respectively). Hypercapnia-induced shear-mediated dilation in the CCA and ICA were assessed in 10 young (5 women and 5 men, 23 ± 1 yr) and 10 older (6 women/4 men, 68 ± 1 yr) healthy adults. Shear-mediated dilation was induced by two levels of hypercapnia (target end-tidal Pco2, +5 and +10 mmHg from individual baseline values) and was calculated as the percent rise in peak diameter from baseline diameter. There were no differences in shear-mediated dilation between young and older adults in either artery under lower levels of hypercapnia (CCA: 2.8 ± 0.6 vs. 2.0 ± 0.3%, P = 0.35; ICA: 4.6 ± 0.8 vs 3.6 ± 0.4%, P = 0.37). However, shear-mediated dilation in response to higher levels of hypercapnia was attenuated in older compared with young adults in the ICA (4.5 ± 0.5 vs. 7.9 ± 1.2%, P < 0.01) but not in the CCA (3.7 ± 0.6 vs. 4.5 ± 0.8%, P = 0.35). Shear-mediated dilation was significantly correlated to the percent change in shear rate in the ICA (young: r = 0.55, P = 0.01; older: r = 0.49, P = 0.03) but not in the CCA in either young or older adults (young: r = −0.30, P = 0.90; older: r = 0.16, P = 0.50). These data indicate that aging attenuates shear-mediated dilation of the ICA in response to higher levels of hypercapnia, and shear rate is an important stimulus for hypercapnic vasodilation of the ICA in both young and older adults. The present results may provide insights into age-related changes in the regulation of cerebral circulation in healthy adults.

NEW & NOTEWORTHY We explored the effect of aging on shear-mediated dilation in the common and internal carotid arteries (CCA and ICA, respectively) in healthy adults. Our findings suggest that 1) aging attenuates shear-mediated dilation of the ICA but not the CCA and 2) shear rate is an important stimulus for hypercapnic vasodilation of the ICA in young and older adults. These findings may provide insights into the age-related changes in cerebrovascular regulation of healthy adults.

Carotid IMT is more associated with stroke than risk calculators

BACKGROUND

It is unclear whether a natural marker of atherosclerosis (carotid intima-media thickness: CIMT) or calculated risk score is more associated with stroke. We therefore comparatively examined the relationship between CIMT as well as two cardiovascular risk calculators (Omnibus Risk Score -ORS and Framingham Risk Score- FRS) and the occurrence of stroke among hypertensive African patients.

METHODS

CIMT was measured in 555 consecutive consenting hypertensive adults (377 stroke patients and 178 stroke-free subjects). The 10-year cardiovascular risk was calculated for each participant with the FRS and ORS. The strengths of association between FRS, ORS, CIMT, and stroke occurrence were examined using logistic regression. The discriminative capacity of FRS, ORS, and CIMT for stroke occurrence was assessed with c-statistics.

RESULTS

Higher average CIMT (OR 11.71; 95% CI 1.65-83.07; P = 0.01) was strongly associated with stroke after adjusting for age, sex, blood pressure, serum cholesterol, and blood sugar. Neither the FRS (OR: 1.03; CI: 0.89-1.19, P = 0.68) nor the ORS (OR: 1.08; CI: 0.90-1.30; P = 0.41) was significantly associated with stroke. CIMT had a higher c-statistic for differentiating stroke patients from hypertensive controls (right: c = 0.63, P < 0.001; left: c = 0.67, P < 0.001; average: c = 0.66, P < 0.001) than some conventional risk factors. Neither FRS (P = 0.39) nor ORS (P = 0.55) was able to independently differentiate between stroke and hypertensive patients.

CONCLUSION

CIMT, but neither FRS nor ORS, is independently associated with stroke among Nigerian African hypertensive patients. CIMT may be a better tool for estimating the overall risk of stroke than FRS or ORS in this population.

Ratio between carotid artery stiffness and blood flow - a new ultrasound index of ischemic leukoaraiosis

Background

Ischemic leukoaraiosis (ILA) is associated with cognitive decline and aging. Its pathophysiology is believed to be ischemic in origin due to its association with cerebrovascular risk factors and similarity in location to lacunar infarctions. ILA diagnosis is still based on magnetic resonance imaging (MRI) as well as exclusion of other causes of white matter hyperintensities. So far, there are no known confirming diagnostic tests of ILA. Ultrasound studies have recently shown increased large artery stiffness, increased cerebrovascular resistance, and lower cerebral blood flow in patients with ILA. Increased arterial stiffness and decreased blood flow could have a synergistic effect, and their ratio could be a useful diagnostic index of ILA.

Methods

In this post hoc analysis, we introduced new ILA indices (ILAi) that are ratios of the carotid stiffness parameters (pulse wave velocity beta [PWVβ], pressure–strain elasticity modulus [Ep], β index), and diastolic and mean blood flows in the internal carotid artery: Q-ICAd and Q-ICAm. We compared the ILAi of 52 patients with ILA and 44 sex- and risk factor-matched controls with normal MRI of the head. ILA diagnosis was based on MRI and exclusion of other causes of white matter hyperintensities. The diagnostic significance of ILAi for the prediction of ILA was analyzed.

Results

All ILAi significantly differed between the groups; the most significant were PWVβ/Q-ICAd (ILA group: 1.96±0.64 vs control group: 1.56±0.40, P=0.001) and PWVβ/Q-ICAm (ILA group: 1.13±0.32 vs control group: 0.94±0.25, P=0.003). All ILAi were significantly associated with ILA (P<0.01) and were significant independent predictors of ILA. All ILAi were also sensitive and specific for predicting ILA (area under the curve: 0.632–0.683, P<0.05).

Conclusion

The new ultrasound indices significantly differed between patients with ILA and the control group and were significant predictors of ILA. A combination of lower carotid blood flow and increased carotid stiffness represented as ILAi probably has a diagnostic value in patients with ILA.

Exploring carotid sonographic parameters associated with stroke risk among hypertensive stroke patients compared to hypertensive controls

OBJECTIVES

Globally, and particularly in low- and middle-income countries, the prevalence of hypertension is increasing with a consequent rise in the burden of stroke. There is a need to identify biomarkers of stroke, which can be used to design stroke prevention programs in these populations. Sonography is an affordable and widely available imaging modality that is ideal for resource-poor countries. We conducted a case-control study to identify carotid sonographic parameters that may be associated with stroke risk among hypertensive patients.

METHODS

Selected demographic, clinical, and laboratory characteristics were collected from 135 consecutive African hypertensive stroke patients and compared with 117 age and sex-matched hypertensive patients with no clinical evidence of stroke, transient ischemic attacks, or ischemic heart disease (controls). The luminal diameter, intima-media thickness, peak systolic velocity (PSV), and end-diastolic velocity (EDV) of the common and internal carotid arteries were measured in all participants, and other carotid parameters, including pulsatility and resistive indices, were derived. Univariate, bivariate, and multivariate analyses were performed

RESULTS

Among hypertensive patients, carotid parameters significantly (P < .05) associated with stroke included a higher diameter and intima-media thickness as well as a lower PSV and EDV in the common carotid and proximal internal carotid arteries. However, the diameter (>6.3 mm; adjusted odds ratio [OR], 8.91; 95% confidence interval [CI], 2.18-36.34; P = .002) and EDV (>21 cm/s; adjusted OR, 0.15; 95% CI, 0.03-0.71; P = .017) of the common carotid artery were the only parameters associated with stroke in multivariate analysis.

CONCLUSIONS

Among hypertensive patients, the common carotid artery diameter and EDV are significantly associated with stroke risk. These findings have implications for development and evaluation of stroke prevention programs.

The relationship of flow velocities to vessel diameters differs between extracranial carotid and vertebral arteries of stroke patients

BACKGROUND

Chronic changes in flow rate through arteries produce adjustment of arterial diameters. We compared the relationship between flow velocity and diameter in the carotid and in the vertebral arteries of stroke patients.

METHODS

Using triplex ultrasonography, the internal diameter and flow velocities of the common carotid, internal carotid, and vertebral arteries of 176 consecutive stroke patients were measured. Correlations were examined with Pearson's statistics at an alpha level of 0.05.

RESULTS

Mean age of the patients was 59.3 ± 12 years, and 66% had cerebral infarcts. Diameter and blood flow velocities showed significant negative correlations (-0.115 ≥ r ≥ -0.382) in the carotid arteries on both sides, but positive correlations (0.211 ≤ r ≤ 0.320) in the vertebral arteries, even after controlling for age, gender, and blood pressure.

CONCLUSIONS

Our study demonstrated different diameter/flow relationships in the carotid and the vertebral arteries of stroke patients, which may suggest pathologic changes in the adaptive processes governing vessel diameter and growth, especially in the carotid arteries.

Common carotid flow velocity is associated with cognition in older adults

AIMS

To assess the relationship between carotid flow velocity and cognitive impairment in patients with mild-moderate (<50%) carotid artery disease.

METHODS

We studied 407 participants with available carotid ultrasound and cognitive measures. We related peak systolic velocity (PSV) and end diastolic velocity (EDV) of internal carotid artery (ICA) and common carotid artery (CCA) and intimal medial thickness (IMT) to Mini Mental State Examination (MMSE), Clock Draw Test (CDT), Activities of Daily Living Scale (ADL)and Montreal Cognitive Assessment (MoCA).

RESULTS

EDV of CCA was significantly different in higher and lower MoCA (MMSE) groups. Multiple regression analysis demonstrated that lower EDV was significantly associated with lower MoCA (+0.459 per standard deviation (SD), p<0. 01 for the left; +0.539 per SD, p<0. 01 for the right) and CDT (odds ratio (OR) 0.093, p< 0.05 for the left; OR) 0.120, p<0. 01 for the right) scores. PSV of left CCA (-0.205 per SD, p<0.05) and IMT (+42.536 per SD, p< 0.001) were associated with ADL. PSV of right CCA was associated with MMSE (+0.081 per SD, p<0.001). No significant relationship between ICA flow velocity and cognitive performance was observed.

CONCLUSIONS

Our preliminary data show that common carotid artery flow velocity was associated with cognitive performance.

Carotid velocities determine cerebral blood flow deficits in elderly men with carotid stenosis <50%

To examine if mild carotid stenosis correlates with silent vascular brain changes, we studied a prospective population-based cohort “Men born in 1914.” Data from followups at ages 68 and 81, have been used. Carotid ultrasound was performed at age 81, and cerebral blood flow (CBF) was measured with SPECT at age 82. Out of 123 stroke-free patients, carotid stenosis <50% was observed in 94% in the right and 89% in the left internal carotid arteries (ICAs). In these subjects, Peak Systolic Velocities in ICA correlated negatively with CBF in a majority of several brain areas, especially in mesial temporal area. Results were limited to normotensive until their seventies, who developed late-onset hypertension with a subsequent blood pressure, pulse pressure, and ankle-brachial index growth. Elderly with asymptomatic carotid stenosis <50% and peak systolic velocities in ICA 0.7–1.3 m/s, should be offered an intensified pharmacotherapy to prevent stroke or silent cerebrovascular events.

Color Doppler sonographic evaluation of flow volume of the internal carotid and vertebral arteries after carotid endarterectomy

BACKGROUND

To measure by Doppler sonography the blood flow volume (BFV) of the ipsilateral and contralateral extracranial internal carotid arteries (ICAs) and both vertebral arteries (VAs) before and after a carotid endarterectomy (CEA) of the ICA. We correlated the result with the degree of stenosis of the ICA.

METHOD

One hundred seven patients who had a CEA were divided into 2 groups. Group I consisted of subjects with stenosis of ipsilateral ICA of >or=70% to near occlusion and Group II included subjects with near occlusion. The Doppler sonographic examinations were performed 1 day before the CEA, 7 days after the CEA, and 1 month after the CEA. The peak systolic velocity, end-diastolic velocity, time-averaged maximum blood flow velocity, resistance index of the ipsilateral ICA, and the BFV of both ICAs and both VAs were calculated.

RESULT

There was a significant increase in the peak systolic velocity, maximum blood flow velocity, and the BFV of the ipsilateral ICA after the CEA. The BFV of the contralateral ICA and both VAs were not significantly altered after the CEA in both groups.

CONCLUSION

The main CEA hemodynamic effect was an increase in the BFV of the ipsilateral ICA regardless of the degree of stenosis.

The relationship between leukoaraiosis volume and parameters of carotid artery duplex ultrasonographic scanning in asymptomatic diabetic patients

The significance of asymptomatic leukoaraiosis is unknown although cerebral microangiopathy is regarded as its pathology. To confirm the relationship between leukoaraiosis and cerebral microangiopathy, the pulsatility index (PI) at the cervical internal carotid artery (CA) which has been proposed as an indicator of microangiopathy, was evaluated in relation to leukoaraiosis. With 122 asymptomatic diabetic patients, leukoaraiosis volume was calculated with magnetic resonance imaging and its correlation with age, microalbuminuria and parameters of extracranial CA duplex ultrasonographic scanning were analyzed. The leukoaraiosis volume correlated with PI on the right side (p=0.027), and intima-media thickness on the left (p=0.017). However multivariate analysis indicated that age alone was a significant independent factor, positively correlating with leukoaraiosis volume on both sides (p<0.0001 on both sides). The underlying pathology of leukoaraiosis should be multifactorial. Further exploration is necessary to distinguish "ischemic" and "non-ischemic" leukoaraiosis.