Kentaro Fujishiro

Correlation of ultrasound-measured common carotid artery stiffness with pathological findings.

To quantitatively and noninvasively evaluate common carotid atherosclerosis in a series of patients, we measured the stiffness parameter beta, which represents the mechanical properties of the vessel. beta was calculated from the relationship between blood pressure and the diameter of the artery as measured by an ultrasonic, phase-locked, echotracking system. Increases in the severity grade of atherosclerosis as subsequently determined at autopsy were correlated with increased beta values in 60 common carotid arteries (r = .68). Patients with beta values greater than 13 had a pathological diagnosis of atherosclerosis in the common carotid artery. The sensitivity of this discrimination ratio was 80%, and the specificity was 80% as well. Thus, beta shows promise as a useful diagnostic indicator for detecting asymptomatic common carotid atherosclerosis.

Correlation of common carotid flow volume measured by ultrasonic quantitative flowmeter with pathological findings.

To evaluate the possibility of quantitatively diagnosing carotid and cerebral atherosclerosis noninvasively, we measured common carotid flow volume in 60 sides (30 patients), using an ultrasonic quantitative flowmeter, and then compared these findings to the severity score of carotid and cerebral atherosclerosis as determined at autopsy. Stenosis decreased common carotid flow volume in the carotid and cerebral arteries. Increases in the severity score varied inversely with reduced flow volume, which was high in inverse correlation (r = -0.696). Patients with flow volumes of 8.5 ml/sec or greater did not have stenosis greater than or equal to 75%, whereas all patients with flow volumes of 6.4 ml/sec or less had stenosis greater than or equal to 50%, with 45% of these having stenosis greater than or equal to 75%. These pathological findings confirm that the common carotid flow volume reflects the degree of carotid and cerebral atherosclerosis present and that the lower limit of common carotid flow volume in healthy subjects is 6.5 ml/sec.

Relationship Between Ultrasound Assessment of Arterial Wall Properties and Blood Pressure

Physical properties of an artery can be described in terms of stiffness, distensibility, and compliance. Changes in these properties can predict atherosclerosis disease, but it is necessary to identify an index that is independent of changes in blood pressure. We measured common carotid artery diameter and pulsatile change with an ultrasonic phase- locked, echo-tracking system in 7 subjects whose mean brachial blood pressure had varied 15 mm Hg or more within a month. Patients taking antihypertensive agents were excluded from the study. We measured changes in arterial diameter (n=41) at least four times during the study period and calculated the pressure-strain elastic modulus (Ep), distensibility coefficient (DC), cross-sectional compliance (CC) and stiffness parameter (β) from inner diameter, its pulsatile change, and blood pressure. The correlation coeffi cients of mean blood pressure with each index are as follows: Ep, 0.53; DC, 0.58; CC, 0.63; β, 0.21. When mean blood pressure increased 1 mm Hg, the change in each index at 100 mm Hg was as follows: Ep, 1.48 ±1.30%; DC, -1.05 ±0.97%; CC, -0.69 ±0.90%; β, 0.45 ±1.11%. Among the four indices that measure the properties of the arterial walls, stiffness parameter β was the least dependent on blood pressure. Thus, it appears to have usefulness as an index of arterial wall sclerosis.

Common carotid artery wall properties in Takayasu's arteritis.

The vessel wall properties of the common carotid artery have been noninvasively and quantitatively assessed with an ultrasonic instrument. Stiffness parameter β, which repre sents the mechanical properties of the vessel, was calculated from the relationship between blood pressure and the diameter of the artery. There are no reports that quan titatively assess wall properties in Takayasus arteritis. The authors compared, in vivo, the vessel wall properties of the common carotid artery in 14 patients with Takayasus arteritis versus those in 60 normal subjects (controls). They measured changes in the inner diameter of the artery between systole and diastole with an ultrasonic, phase-locked, echo-tracking system. β was significantly higher in Takayasus arteritis than in normal subjects (better than a 99% confidence interval). The findings for each decade were as follows: 3rd decade (20s): 35.7 ±28.9 vs 5.01-6.46, P=0.0001; 4th decade (30s): 19.5 ±9.71 vs 6.09-7.80, P=0.02; 5th decade (40s): 26.2 ±11.3 vs 7.26-9.28, P=0.0001; 6th decade (50s): 19.1 ±4.27 vs 8.66-11.25, P=0.0001. Takayasus arteritis significantly impaired the mechanical performance of the common carotid artery. Thus, β shows promise as a useful diagnostic indicator of Takayasus arteritis.