Current status of carotid ultrasound in atherosclerosis.

Cardiovascular disease (CVD) primarily caused by atherosclerosis is a major cause of death and disability in developed countries. Sonographic carotid intima-media thickness (CIMT) is widely studied as a surrogate marker for detecting subclinical atherosclerosis for risk prediction and disease progress to guide medical intervention. However, there is no standardized CIMT measurement methodology in clinical studies resulting in inconsistent findings, thereby undermining the clinical value of CIMT. Increasing evidences show that CIMT alone has weak predictive value for CVD while CIMT including plaque presence consistently improves the predictive power. Quantification of plaque burden further enhances the predictive power beyond plaque presence. Sonographic carotid plaque characteristics have been found to be predictive of cerebral ischaemic events. With advances in ultrasound technology, enhanced assessment of carotid plaques is feasible to detect high-risk/vulnerable plaques, and provide risk assessment for ischemic stroke beyond measurement of luminal stenosis.

Compensatory patterns of collateral flow in stroke patients with unilateral and bilateral carotid stenosis.

BACKGROUND: Collateral pathways are important in maintaining adequate cerebral blood flow in patients with carotid stenosis. We aimed to evaluate the hemodynamic patterns in relation to carotid stenosis in acute stroke patients. METHODS: Consecutive 586 stroke patients in a hospital based cohort were included in the present study. Carotid duplex was performed to identify patients with absolute minimal diameter reductions of 50% or greater in their internal carotid arteries (ICAs). Color velocity imaging quantification ultrasound (CVIQ) was used to measure extracranial arterial blood flow volume (BFV) in bilateral common carotid arteries (CCAs) and bilateral vertebral arteries (VAs). The absolute values of BFV and the ratios were compared between patients with and without ICA stenosis. RESULTS: Among 586 acute ischemic stroke patients (mean age: 67.5 ± 12.4y), ICA stenosis was detected in 112 patients (19.1%), including unilateral ICA stenosis in 81 patients (13.8%) and bilateral ICA stenosis in 31 patients (5.3%). Among patients with unilateral ICA stenosis, the BFV in contralateral CCA was significantly higher than that in ipsilateral CCA (325.5 ± 99.8 mL/min vs. 242.2 ± 112.2 mL/min, P < 0.001). Among patients with bilateral ICA stenosis, the sum of BFV in bilateral VAs accounted for 22% of the whole cerebral blood flow, which was significantly higher than that in those without ICA stenosis (14.8%, P < 0.001) or with unilateral ICA stenosis (16.9%, P = 0.007). CONCLUSIONS: In patients with unilateral carotid stenosis, contralateral carotid blood flow increases to compensate decreased blood flow, while posterior circulation may compensate for the decreased brain perfusion in those with bilateral carotid stenosis.

Differential associations of traditional and non-traditional risk factors with carotid intima-media thickening and plaque in peritoneal dialysis patients.

BACKGROUND: This study sought to examine the associations of traditional and non-traditional cardiovascular risk factors with carotid intima-media thickening and plaque in peritoneal dialysis (PD) patients. METHODS: A cross-sectional study was performed in 147 PD patients with carotid intima-media thickness (IMT) and plaque assessed by B-mode ultrasonography and fasting blood collected for biochemical measurements. RESULTS: On univariate analysis, age, smoking history, fibrinogen, C-reactive protein (CRP), adiponectin, fetuin-A, lipoprotein(a) and diastolic blood pressure were associated with carotid IMT while age, smoking history, diabetes, CRP and diastolic blood pressure were associated with carotid plaque. Using multivariate analysis, elevated CRP (p = 0.015) and serum calcium (p = 0.022) were associated with carotid plaque but not with IMT. CRP and serum calcium were synergistically associated with carotid plaque in that those with CRP > median and serum calcium > median showed the highest prevalence of carotid plaque than either factor alone (p = 0.003). CONCLUSIONS: An elevated CRP appeared to be a better biomarker of presence of carotid plaque than intima-media thickening. Furthermore, CRP and serum calcium showed synergistic association with presence of carotid plaque. However, our study was limited by the cross-sectional design and baseline laboratory abnormalities were inevitably confounded by the treatment already given, resulting in difficulty to distinguish cause and effect relationship. Nevertheless, these observations warrant further investigation as it may potentially have important implications on differentiating therapeutic strategies for reducing carotid IMT and plaque progression in PD patients.

Cardiac valvular calcification as a marker of atherosclerosis and arterial calcification in end-stage renal disease.

BACKGROUND: Patients with end-stage renal disease (ESRD) are at increased risk for tissue calcifications as a result of deranged mineral metabolism. We tested the hypothesis that valvular calcification is a marker of atherosclerosis in patients with ESRD. METHODS: Echocardiography was performed in 92 patients undergoing peritoneal dialysis with no background atherosclerotic vascular complications to detect valvular calcification. We used B-mode ultrasonography to determine carotid artery intima-media thickness and the presence of plaque and calcification. RESULTS: Compared with patients without valvular calcification (n=66), those with valvular calcification (n=26) had higher C-reactive protein levels (P=.01) and greater mean +/- SE carotid intima-media thickness (1.12 +/- 0.06 vs 0.88 +/- 0.04 mm; P=.003). Carotid artery calcification was present unilaterally and bilaterally in 4 patients (15%) and 17 patients (65%) with valvular calcification vs 11 (17%) and 14 (21%) without, respectively (P<.001). Carotid artery plaque was present unilaterally and bilaterally in 11 patients (12%) and 16 patients (65%) with valvular calcification vs 3 (17%) and 17 (24%) without, respectively (P=.001). Using multiple logistic regression analysis, every 1-mm increase in carotid intima-media thickness was independently associated with a 6.51-fold (95% confidence interval, 1.58-26.73; P=.009) increased risk of valvular calcification, and calcification and plaque in the carotid arteries were associated with a 7.18-fold (95% confidence interval, 2.39-21.51; P<.001) and a 5.00-fold (95% confidence interval, 1.77-14.13; P=.002) increased risk of valvular calcification, respectively. CONCLUSION: The associations among valvular calcification, inflammation, carotid atherosclerosis, and arterial calcification suggest that valvular calcification is a marker of atherosclerosis and arterial calcification in patients with ESRD.

Cerebral blood flow measurement by color velocity imaging in radiation-induced carotid stenosis.

OBJECTIVE: To show whether there is any association between the development of neurologic symptoms and the total cerebral blood flow volume documented by color velocity imaging in patients with carotid stenosis that develops after radiotherapy. METHODS: Twenty-three patients with nasopharyngeal carcinoma (4 female and 19 male; age range, 39-69 years; mean age, 55.6 years) and major extracranial carotid stenosis underwent color velocity imaging. In this group, 8 patients had symptoms of a stroke or transient ischemic attack, and the other 15 patients were asymptomatic. The color velocity imaging results in the symptomatic group were then compared with those in the asymptomatic group. RESULTS: The cerebral blood flow in the symptomatic group was significantly lower than that in the asymptomatic group (224.1 +/- 89.0 versus 532.5 +/- 89.0 mL/min; P = .001). CONCLUSIONS: Cerebral blood flow as measured by color velocity imaging was lower in the symptomatic group. There is an association between the development of neurologic symptoms and blood flow volume.

Blood flow volume quantification of cerebral ischemia: comparison of three noninvasive imaging techniques of carotid and vertebral arteries.

OBJECTIVE: Determination of blood flow volume is useful in assessing ischemic cerebrovascular disease. We compared the blood flow volume measurement of three noninvasive imaging techniques, namely color velocity imaging quantification, spectral Doppler imaging quantification, and MR phase-contrast flow quantification, to see how well the flow values determined by each technique agreed with one another. SUBJECTS AND METHODS: Flow volume quantification was tested experimentally using a flow simulator and by the three techniques in the vertebral and internal carotid arteries of 40 patients with histories of cerebral ischemia. In the flow simulation study, the flow values in each technique were compared with the phantom flow by the Wilcoxon's signed rank test. In the patient study, the flow values between each paired technique were compared by paired t test. The significance level was taken at p less than 0.05. RESULTS: Flow volumes were measured by color velocity imaging quantification. MR phase-contrast flow quantification agreed with the phantom flow simulation within the tested range, and spectral Doppler imaging quantification values were significantly overestimated. In patients, a large variation of the blood flow volume was obtained between each technique (p < 0.05). Among them, spectral Doppler imaging quantification showed the highest flow values in the vessels (internal carotid arteries, 312.6 mL/min; vertebral arteries, 112.0 mL/min), followed by color velocity imaging quantification (internal carotid arteries, 216.8 mL/min; vertebral arteries, 58.1 mL/min) and MR phase-contrast flow quantification (internal carotid arteries, 169.1 mL/min; vertebral arteries, 66.5 mL/min). CONCLUSION: Blood flow volume measurements determined by the three noninvasive imaging techniques on the same vessel can differ widely, and spectral Doppler imaging quantification consistently overestimated the flow volume. It is, therefore, essential that the same technique, preferably color velocity imaging quantification or MR phase-contrast flow quantification, be used for clinical follow-up investigations in the future.