Ultrasonically assisted evaluation of the impact of atherosclerotic plaque on the pulse pressure wave propagation: a clinical feasibility study.

The purpose of this work was to evaluate ultrasound modality as a non-invasive tool for determination of impact of the degree of the atherosclerotic plaque located in human internal carotid arteries on the values of the parameters of the pulse wave. Specifically, the applicability of the method to such arteries as brachial, common, and internal carotid was examined. The method developed is based on analysis of two characteristic parameters: the value of the mean reflection coefficient modulus |Γ|(a) of the blood pressure wave and time delay Δt between the forward (travelling) and backward (reflected) blood pressure waves. The blood pressure wave was determined from ultrasound measurements of the artery's inner (internal) diameter, using the custom made wall tracking system (WTS) operating at 6.75 MHz. Clinical data were obtained from the carotid arteries measurements of 70 human subjects. These included the control group of 30 healthy individuals along with the patients diagnosed with the stenosis of the internal carotid artery (ICA) ranging from 20% to 99% or with the ICA occlusion. The results indicate that with increasing level of stenosis of the ICA the value of the mean reflection coefficient measured in the common carotid artery, significantly increases from |Γ|(a)=0.45 for healthy individuals to |Γ|(a)=0.61 for patients with stenosis level of 90-99%, or ICA occlusion. Similarly, the time delay Δt decreases from 52 ms to 25 ms for the respective groups. The method described holds promise that it might be clinically useful as a non-invasive tool for localization of distal severe artery narrowing, which can assist in identifying early stages of atherosclerosis especially in regions, which are inaccessible for the ultrasound probe (e.g. carotid sinus or middle cerebral artery).

Is the resistance of large conduit arteries also decreased in thyrotoxic patients with Graves' disease?

Longitudinal arterial resistance (RL) originates during blood flow in large conduit arteries while peripheral resistance (RP) reflects the tension of arterioles. Using a new noninvasive ultrasonic system of assessment of mechanical properties of arterial walls, we aimed to discover whether both RL and RP are affected by excess of thyroid hormones (TH). We compared two groups: hyperthyroid (Graves' group, n = 25) and euthyroid (control group, n = 23). RL and RP values were obtained from the analysis of the four-element lumped parameters model describing the vascular input impedance. The vascular input impedance was determined on the basis of simultaneous measurements of blood pressure, blood flow and arterial diameter using oscillometric and ultrasonic methods. RL and RP were lower in the Graves' group (3.71 +/- 1.98 versus 4.49 +/- 1.81 10(8)kgm(4)s(1), p < 0.05 and 8.43 +/- 3.56 versus 11.23 +/- 2.69 0(8)kgm(4)s(1), p < 0.00002, respectively). There was strong correlation between RP and TH in the Graves' group (r(s)= -0.6710, p = 0.000001 for RP and free triiodothyronine (FT3); r(s)= -0.4683, p < 0.001 for RP and free thyroxine [FT4]). This relationship remained significant after the statistical correction for total cholesterol (r(p)= -0.7064 p = 0.0000001 for RP and FT3). No similar correlation between RL and TH was found what suggests a different character of relations between TH and RL and between TH and RP.

The stiffness of the common carotid artery in patients with Graves' disease.

BACKGROUND: Thyroid hormone excess is accompanied by many cardiovascular symptoms. We hypothesised that mechanical properties of the large arteries are also involved in hyperthyroidism-induced cardiovascular changes and set out to investigate this further. METHODS: We compared 2 groups: one composed of hospitalized patients with newly diagnosed, non-treated Graves' disease (Graves' group) and the other (control group) composed of healthy persons or patients with euthyroid goiter (n=25 and n=23, respectively). We determined values of cross-sectional compliance (CC(100)), distensibility (DC(100)) and stiffness coefficients (alpha(100)) estimated for blood pressure P(n)=100 mmHg by measuring the blood pressure with the oscillometric method and measuring differences in the diameter of the common carotid artery with ultrasonographic vascular echo Doppler system. RESULTS: We found no differences in CC(100) (10.6 vs 10.3 10(-4)m(2)/Mpa), DC(100) (29.7 vs 29.6 1/Mpa) or alpha(100) (2.67 vs 2.72) between the 2 groups. However, there were strong correlations between all stiffness parameters and plasma thyroid hormone concentrations in the Graves' group (r(s)=0.4698, p<0.001 for DC(100), r(s)=0.4342, p<0.003 for CC(100), r(s)=-0.4698, p<0.001 for alpha(100) and fT3, respectively). This relationships remained significant after statistical corrections for age and lipid levels (r(p)=0.22, p<0.03 for DC(100) and fT3 or r(p)=-0.457, p<0.02 for alpha(100) and fT3, respectively). CONCLUSIONS: These results indicate that in the Graves' group the stiffness of the common carotid artery might be affected by the thyroid hormone level and the lower the level, the more severe the activity of the hyperthyroidism reflected by the plasma concentration of fT3 or fT4.

[Transcutaneous balloon angioplasty in the treatment of subclavian steal syndrome. Characteristics of vertebral basal flow with transcranial Doppler technique]. / Przezskórna angioplastyka balonowa w leczeniu zespolu podkradania tetnicy podobojczykowej. Charakterystyka parametrów przeplywu krwi w krazeniu podstawno-kregowym technika transcranial Doppler.

Subclavian steal syndrome (SSS) appears when the origin of the subclavian artery (SA) is occluded or stenosed. Introduction of transcranial Doppler sonography (TCD) provided an opportunity to evaluate parameters of the blood flow in the vertebral (VA) and basilar artery (BA). Measurements of blood flow velocities performed at rest and after the brachial hyperemia test allow one to classify hemodynamic types of SSS. The aim of the study was to categorize types of steal and to compare the differences of flow patterns before and after percutaneous transluminal SA balloon angioplasty (SA-PTA). Fourty-eight patients with angiographically confirmed SSS (aged from 27 to 68 years, mean 53; 2/1 f/m ratio) were examined with 2 MHz range-gated, pulsed transcranial Doppler device (TC 2-64B EME). Both VA and BA were evaluated by the transoccipital approach at rest and during the brachial hyperemia. In 5 cases (10.4%) permanent reversal blood flow in the BA was observed (complete basilar steal). In flow in the BA blood flow was in the normal direction at rest and altered (reversed or decreased) when induced with brachial hyperemia test (transient basilar steal). In the next 14 patients (29.2%) permanently reversed VA blood flow was observed with only a slight or no alterations of the BA flow after the hyperemia test (complete vertebral steal). In the last 19 cases (39.6%) alterations of the VA blood flow without changes in BA flow were observed (latent vertebral steal). Between 1991 and 1994 twenty seven symptomatic patients with different hemodynamic types of SSS were treated with SA-PTA. TCD evaluation of VA's and BA using the hyperemia test was performed before, 3 to 7 days and 3 months after morphologically and hemodynamically successful subclavian artery balloon PTA. Normal results of vertebrobasilar examinations were obtained in 26 cases after this procedure. In one case the latent vertebral steal was detected. The 28 months mean follow-up revealed no significant changes in TCD flow patterns recorded from VA's and BA. After collecting data of about 60 patients with SSS we examined with TCD we conclude that: in patients with a hemodynamically significant SA stenosis the presence of reversed ipsilateral VA blood flow (a radiologic steal) its not a good determinant of either the presence or type of presenting symptoms and after successful PTA or recanalisation and PTA of SA in almost all cases we examined close to normal TCD recordings in BA and VA.

The effect of internal carotid artery elongation on intracranial blood flow.

Redundant length of the cervical part of the internal carotid artery (ICA) is a clear angiographic entity although the clinical significance is uncertain. Transcranial Doppler sonography (TCD) examinations were performed on 15 patients with 23 elongated ICAs. The recordings were obtained with the use of flat 2 MHz probe from the middle cerebral artery (MCA) and the intracranial part of ICA at rest and in eight possible extreme positions of head and neck rotation. The mean blood flow velocity in the intracranial part of the ICA obtained in the neutral position was 50.1 +/- 8.3 cm s-1 and after head and neck rotations was 49.8 +/- 9.5 cm s-1. The mean blood flow velocity in the MCA was 55.8 +/- 6.7 cm s-1 and did not change significantly after head and neck movements (54.9 +/- 7.6 cm s-1). Analysis of 368 one minute recordings from all possible head positions showed no significant changes of blood flow velocity. Rotation of the head and neck has no significant influence on intracranial blood flow velocity in the presence of carotid artery elongation.

Collateral role of the external carotid artery and its branches in occlusion of the internal carotid artery.

In 40 patients with unilateral occlusion of the internal carotid artery, using a transcranial Doppler device, blood flow velocity in the ipsilateral ophthalmic and middle cerebral artery was registered. During compression of the ipsilateral common carotid artery a decrease of ophthalmic artery flow velocity was noted in 39 patients (97.5%) and a decrease of middle cerebral artery flow velocity in 8 patients (20%). The average decrease of mean velocity in the middle cerebral artery was 4.5% of the initial value. During compression of the ipsilateral superficial temporal and facial arteries ophthalmic artery flow velocity decreased in 10 patients (25%) and no marked decrease of middle cerebral blood flow was noted. Conclusions. The external carotid artery in most of the patients with internal carotid occlusion is of no significance for cerebral blood supply, but it is the most important source of collateral blood supply to the eye. The maxillary artery, and not superficial temporal and facial as it seemed in periorbital Doppler examinations, is the branch of the greatest collateral value for the eye and brain.

[Vision disorders as the first symptom of cerebrovascular insufficiencycaused by the changes in the carotid arteries. Studies using the transcranial Doppler ultrasonic apparatus TC2-64B]. / Zaburzenia widzenia jako pierwszy objaw niedostatecznosci ukrwienia mózgu spowodowanego zmianami w tetnicach szyjnych. Badania przy zastosowaniu transcranial Doppler TC2-64-B.

Investigations were carried out in 25 patients with carotid arteries changes. A 2 MHz head was used. Direction of the flow, the average speed and index of pulsation were determined. The results were compared with examinations in 13 healthy subjects. Disturbances of vision were shown by 11 patients (44 p.c.). A normal direction of blood perfusion was observed in 8 arteries (25 p.c.), a reversed one in 22 (69 p.c.), in 2 patients no Doppler's signal could be obtained. In arteries with a reversal flow of blood the authors observed the maximal mean speed and the lowest pulsation index. In neither case did the ophthalmological examinations reveal any embolic material. It seems that visual disturbances in patients with carotid arteries changes may be caused by a change of direction of the blood flow from a normal to a reversed one.