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In a prospective study using a multigate pulsed Doppler system, minor (less than 30% diameter reduction) carotid artery lesions were diagnosed by detecting not only abnormalities in the blood flow pattern, but also local changes in artery wall distensibility. For the diagnosis of more severe lesions, additional information was obtained from disturbances in the Doppler audio spectrum. Biplane arteriography was used as a reference. The observed agreement, sensitivity, and specificity were 86.6%, 90.3%, and 88.6%, respectively, for all lesions and 85.7%, 82.1%, and 88.6%, respectively, when only minor lesions were considered. kappa (a chance-corrected measure of agreement) was 81.7%. If only blood flow abnormalities were used to detect minor lesions, 43.5% would be missed. Our results indicate that minor carotid artery lesions can be diagnosed noninvasively more accurately when both local blood flow irregularities and local changes in vessel wall distensibility are taken into account.

In the present study the criteria of spectral broadening used in pulsed Doppler systems to diagnose minor disease in the cervical carotid arteries were evaluated in relation to the size of the sample volume. For this purpose the Doppler audio spectra as recorded in asymptomatic volunteers with an ATL Duplex scanner (relatively large sample volume) and a multi-gate pulsed Doppler system (relatively small sample volume) were compared with each other. The volunteers, randomly selected from the population registers, varied in age from 20-69 yr. Only in the common carotid artery at younger age, were normal spectra recorded, especially with the multi-gate system. In the internal carotid artery the number of spectra, supposed to be associated with low grade stenosis, increased significantly, especially when recorded with the Duplex scanner. More pronounced spectral broadening was found when the spectra were recorded distally in this artery. In the cervical carotid arteries normal spectra were found only when sampled in the middle of the bloodstream. These findings indicate that for the detection of vascular lesions in the cervical carotid arteries at an early stage of the disease on the basis of spectral broadening, small sample volumes and sampling in the centre of the vessel are required.

Basically two principles have to be distinguished in ultrasonic imaging of arteries. In velocity imaging blood flow velocities are visualized with continuous wave or pulsed Doppler devices. In pulsed echo-systems artery wall structures are visualized by picking up echoes reflected by the vessel walls. Velocity imaging is mainly used to localize the site of velocity sampling which is of importance in screening the carotid artery bifurcation and in follow-up studies. Although promising results have been obtained in diagnosing atherosclerotic lesions with echo-imaging systems, these systems have their limitations. To improve the diagnostic accuracy these systems should be combined with a single- or multi-gate pulsed Doppler system.

The vessel wall properties of the common carotid artery were noninvasively studied in 109 normotensive, presumed normal male and female volunteers of various ages (20-69 y) with the use of a multi-gate pulsed Doppler system. This system allows the on-line recording of velocity profiles and the relative changes in carotid artery diameter during the cardiac cycle (delta d/d). From the width of these profiles the systolic internal diameter (d) of the carotid artery can be determined. With the use of d, the maximal increase in delta d/d during systole and the pulse pressure, as measured in the brachial artery (delta p), the distensibility coefficient and the cross-sectional compliance were calculated. Both distensibility and cross-sectional compliance were significantly lower in females than in males, irrespective of age. This likely results from a stiffer arterial wall behavior in females, because the relative increase in vessel diameter during the cardiac cycle is lower in females than in males, despite the fact that their pulse pressure values are not significantly different. The carotid artery diameters were similar in men and women. The findings in the present study indicate that the common carotid artery is stiffer in females than in males of comparable age. Therefore, sex-dependent differences have to be considered in the interpretation of arterial distensibility and cross-sectional compliance.

The vessel wall properties of the common carotid artery were studied noninvasively in normotensive and borderline hypertensive male volunteers of various ages with the use of a multi-gate pulsed Doppler system. In the younger age group (20-35 y) both distensibility and cross-sectional compliance were significantly less in the borderline hypertensive group. In the older borderline hypertensive subjects (50-69 y) distensibility (p less than 0.05) and cross-sectional compliance (p = 0.06) were also less than in the control subjects. The reduced distensibility and cross-sectional compliance likely result from a decrease in arterial wall elasticity because the relative increase in common carotid artery diameter during systole is diminished in borderline hypertensives, despite the fact that their pulse pressure is similar to or higher than that in control subjects. The less pronounced differences in vessel wall properties between borderline hypertensive and normotensive volunteers in the older age group may be a consequence of the changes in these properties with age, partly masking the alterations due to borderline hypertension. Since the stiffer behavior of the common carotid artery in borderline hypertensives is associated with relatively slight changes in blood pressure, the question can be raised whether the alterations in arterial wall properties are really a result of the elevated arterial blood pressure; these alterations might develop independent of the blood pressure elevation.

Changes in distensibility and cross-sectional compliance of the common carotid artery with age were studied in 80 presumed healthy volunteers, varying in age between 20 and 69 y. The distensibility was assessed from the relative increase in arterial diameter during systole normalized with respect to the arterial pulse pressure. The cross-sectional compliance was obtained by multiplying the distensibility by the arterial diameter. The relative diameter changes of the common carotid artery during the cardiac cycle were recorded on-line with a high resolution multigate pulsed Doppler system. The arterial diameter was assessed from the width of the velocity profiles which can also be recorded on-line with this system. Arterial pulse pressure was determined from brachial artery cuff blood pressure measurements. Both distensibility and cross-sectional compliance of the common carotid artery decreased linearly with age, starting in the third age decade. The reduction in the latter parameter was less pronounced, probably as a consequence of an increase in arterial diameter with age.

The diagnostic accuracy of noninvasive detection of carotid artery lesions with a diameter of less than 50% (minor to moderate) and greater than 50% reduction (severe) with the use of a multi-gate pulsed Doppler system (spectral analysis combined with the detection of flow disturbances) was studied in patients with focal neurological symptoms. Biplane arteriography was used as a reference. For all lesions the diagnostic accuracy (observed agreement), sensitivity and specificity was 88, 92, and 84%, respectively, and 84, 83, and 84%, respectively, when only minor to moderate lesions were considered. Kappa, a chance-corrected measure of agreement, which takes into account the marginal distribution of the data and, hence, may be considered to be a better parameter to describe diagnostic accuracy, was found to be 82.2%. The results in this study compare favorably with those obtained in studies employing duplex techniques (B-mode image combined with single-gate pulsed Doppler) and indicate that minor to moderate carotid artery lesions are detected rather accurately with the use of a multi-gate pulsed Doppler system.