Carotid blood flow measured by an ultrasonic volume flowmeter in carotid stenosis and patients with dementia

Extracranial internal carotid artery occlusion: the role of common carotid artery volume flow

BACKGROUND AND PURPOSE

Quantitative measurement of blood flow volume in the common carotid artery (CCA) is now possible using the color velocity imaging quantification (CVI-Q) ultrasound technique. The aim of this study was to evaluate the cerebral hemodynamic effects of unilateral internal carotid artery (ICA) occlusion on CCA blood flow volumes (FVs) using CVI-Q.

METHODS

Records of ultrasound studies in our neurosonology laboratory were retrospectively reviewed to identify patients with unilateral ICA occlusions who at a minimum received both a routine color duplex carotid ultrasound examination and quantitative measurement of FV in the CCA, bilaterally, using the CVI-Q method. A total of 71 patients met criteria and were included in the cohort. A side to side comparison was performed for FV, peak systolic velocities (PSV), end-diastolic velocities (EDV), and resistance indices (RIs) in the CCA. Results correlated with any other available data such as flow direction in the ophthalmic artery and the presence of intracranial collateralization.

RESULTS

The FV, PSV, and EDV were significantly reduced, and the RI was significantly increased in the CCA on the side of the occlusion. A subgroup analysis in patients who also had an examination of the ophthalmic (n = 61) and the intracranial arteries of the Circle of Willis (n = 50), showed significantly higher FV in the CCA on the side of the occlusion if there was also reversed flow in the ophthalmic artery on the side of the occlusion (344 +/- 144 ml/min versus 169 +/- 53 ml/min).

CONCLUSION

Quantitative FV measurement using CVI-Q ultrasound can identify clear alterations in volume flow, collateral pathways, and cerebral hemodynamics in patients with unilateral ICA occlusion. It is a complementary tool, providing additional objective information about the cerebral hemodynamic effects of ICA occlusion that goes beyond what is available using routine flow velocity data.

Cross-beam vector Doppler ultrasound for angle-independent velocity measurements

Combining Doppler measurements taken along multiple intersecting ultrasound (US) beams is one approach to obtaining angle-independent velocity. Over 30 laboratories and companies have developed such cross-beam systems since the 1970s. Early designs focused on multiple single-element probes. In the late 1980s, combining multiple color Doppler images acquired from linear-array transducers became a popular modality. This was further expanded to include beam steering and the use of subapertures. Often, with each change in design, came a new twist to calculating the velocity. This article presents a review of most proposed cross-beam systems published to date. The emphasis is on the basic design, the approach used to determine the angle-independent velocity, the advantages of the design, and the disadvantages of the design. From this, requirements needed to convert the idea of angle-independent vector Doppler into a commercial system are suggested.

Pathogenetic mechanisms in vascular dementia

Vascular dementia accounts for approximately 20% of all cases of dementia and for about 50% in subjects over 80 years. Thromboembolism with multiple cerebral infarcts was considered to be almost the only pathogenetic pathway of vascular dementia, with multi-infarct dementia as its clinical manifestation. However, there is a great heterogeneity of vascular dementia syndromes and pathological subtypes, as documented by the number of pathogenetic mechanisms now known to underlie the clinical picture. They include thromboembolism and extracerebral and cerebral factors. Among the extracerebral factors are ischemic hypoxic dementia (i.e., dementia due to hypoperfusion), vasculitis, hyperviscosity and abnormalities of hemostasis. Among the cerebral factors are lipohyalinosis, cerebral amyloid angiopathy, disruption of the blood-brain barrier and altered regulation of cerebral blood flow. Therefore, the approach to vascular dementia should take the heterogeneity into account. In this context, the importance of non-infarct type should be considered; subcortical white matter disorder seems to be a noteworthy common pathway of vascular dementia produced by various vascular mechanisms. Finally, the heterogeneity of the vascular mechanisms involved in vascular dementia--namely hypoperfusion--might be a factor that can be positively influenced by targeted therapeutic intervention.

Heterogeneity of vascular dementia: mechanisms and subgroups

Today, multiple, thromboembolically generated cerebral infarcts are regarded as the main pathogenetic pathway of vascular dementia (VAD), with multi-infarct dementia (MID) as its clinical counterpart. However, taking into account other vascular mechanisms that may influence the brain, such as vessel-wall damage (atherosclerosis, hyalinosis, amyloid angiopathy, or blood-brain barrier dysfunction), cerebrovascular insufficiency (disturbance of systemic circulation, perfusion vulnerability related to the vascular anatomy of the brain, or disturbance of autoregulation), and hyperviscosity, it is evident that MID is not the only VAD category. The diagnosis of MID ought to be reserved for the combination of progressive dementia associated with cerebral ischemic events and evidence of infarction that is mainly associated with the large cerebral arteries. Subcortical white-matter dementia characterized by frontosubcortical symptomatology, white-matter lesions, and small-vessel involvement with or without lacunes/infarcts--a combination of lacunar dementia and Binswanger's disease--appears to be another important VAD disease.

Difference in blood flow volume of the common carotid artery between vascular and non-vascular dementia detected by colour duplex sonography

Using colour duplex sonography, blood flow volume in the common carotid artery was measured in 72 demented patients and 28 normal controls. Thirty-five patients with a Hachinski's ischaemic score of 7 or above and marked ischaemic lesions on CT were assigned to the vascular dementia (VD) group. Thirty-three patients with probable Alzheimer's disease according to the NINCDS-ADRDA criteria, 2 patients with Parkinson's disease, 1 patient with spinocerebellar degeneration, and 1 patient with Pick's disease were assigned to the non-vascular dementia (nonVD) group. The sum of blood flow volume in the bilateral common carotid arteries (CCA flow) in the nonVD group and in the VD group was lower than that in the control group. The CCA flow in the VD group was lower than that in the nonVD group. Comparison of patients matched for both age and the Hasegawa's dementia rating scale also revealed lower CCA flow in the VD group than in the nonVD group. Linear discriminant function analysis showed that nearly 90% of the demented patients were correctly diagnosed as having VD or as having nonVD. These results show the usefulness of colour duplex sonography in the differential diagnosis of patients with dementia.

A study of common carotid arterial blood flow volume of nursing home residents

Ninety-seven nursing home residents were divided into 2 groups according to whether they had had an episode of stroke or not. Each group was classified into 3 subgroups: prolonged bed rest, walking with aids or walking by themselves. They were investigated for both the carotid blood flow volume and the modified Stockton geriatric rating scale (SGRS). In chronic stroke residents, the total blood flow volume of prolonged bed rest residents was lower than that who can walk by themselves. In residents without stroke, the total blood flow volume of prolonged bed rest residents was lower than the other 2 subgroups. The total blood flow volume was significantly correlated with the scores of 3 factors of the modified SGRS.

Blood flow velocity waveform in the common carotid artery and its analysis in elderly subjects

We investigated common carotid artery blood flow in 99 elderly nursing home residents using an ultrasonic quantitative blood flow measurement system. Systolic velocity and end-diastolic velocity were obtained from the waveform and classified, using the end-diastolic/systolic volume as Type A which is normal flow (greater than 20% bilaterally), Type B which is unilateral decreased flow (less than 20% unilaterally), Type C which is bilateral decreased flow (less than 20% bilaterally), Type D which is Type C plus a saw tooth pattern and Type E which is no diastolic pattern, i.e. a value of 0 unilaterally or bilaterally. Five per cent of subjects showed Type A of blood flow velocity waveform (normal flow pattern) and about 40% showed Type E (no diastolic pattern). The subjects were divided into three groups according to blood flow velocity waveform. Groups 1, 2 and 3 showed Types A or B, C or D, and E, respectively. The total blood flow volume and mean blood flow velocity of Group 1 were significantly higher than those of Groups 2 and 3 in both the supine and sitting positions. Although both total blood flow volume and mean blood flow velocity of Group 1 decreased significantly in postural change, those of Groups 2 and 3 did not change. These results suggest that total blood flow volume and mean blood flow velocity decrease in proportion to changes in the blood flow velocity waveform.

Relationship between common carotid arterial flow and age in nursing home residents

Heart rate and carotid blood flow were measured in 82 elderly nursing home residents in both supine and sitting positions. The subjects had been divided into two groups according to whether or not they had had an episode of chronic cerebrovascular disease. In subjects with chronic cerebrovascular disease, the heart rate in the sitting position was significantly (P less than 0.01) faster than that in the supine position but there were no significant differences in total carotid blood flow volume or in mean carotid blood flow velocity between the positions. In subjects with chronic cerebrovascular disease, there were also no significant correlations between heart rate, total blood flow volume, or mean blood flow velocity, in either position, and age. In subjects without chronic cerebrovascular disease, the results for postural change were the same as those in subjects with chronic cerebrovascular disease but in both positions there was a significant negative correlation between age and both total carotid blood flow volume and mean carotid blood flow velocity.