| The circulation system damage led by essential hypertension has become an important factor in morbidity and mortality. of middle- aged and aged people. Hypertension can affect every vitals all over the body, and lesions of artery vascular are the main reason of hypertension complication. The change of arteries elasticity is one of early sign in essential hypertension. As the window of atherosclerosis clinical manifestations, carotid elasticity early detection is beneficial to early finding of arteries change in essential hypertension.Strain is the deformation ability of objects' response after stress,and also is the length variation per unit length. Strain rate is the velocity of deformation, and also is the strain per unit time. Velocity vector imaging (VVI) is the new ultrasonic technology in evaluation of cardiovascular wall structural mechanics, it does not depend on Doppler principle, imaging raw information including spatialization information can be obtained using the technology of ultrasonic pixel of spatial coherence, pixel tracking and boundary tracking on the base of the two-dimension gray scale imaging. Pictures, data, curves and color tri- dimensional graphs can be got according to needs. VVI technology uses line segment with arrow to represent the motions of cardiovascular wall, length of line segment representing the magnitude of velocity and direction of line segment representing the direction of velocity. It is based on pixel tracking principle, and reflects motional information of vascular wall in each direction with less noise and no-dependence on angle compared with the traditional tissue Doppler technology. It can automatically determine the centre of centripetence by following common carotid artery intima according to tracking points, and has enhanced the repeatability of detection. The common carotid arteries both in sixty patients with different degree hypertension and twenty objects as the normal control group were examined with VVI by SIEMENS ACUSON Antares color Doppler ultrasonic imager. The systolic maximum velocity (Vs), maximum strain (Smax) and maximum strain rate (SRmax) of common carotid arterial wall along the short axis in both case and control group were measured to reveal the motion state of case group and supply a new observation method of large artery elasticity abnormality in essential hypertension. The study shows that the Vs of frontal wall and lateral wall of common carotid arterial along the short axis are higher than that of posterior wall and medial wall in control group,which has coincidence with the study of Wangqi's, it may be correlated to the anatomical position of common carotid artery, the motion of posterior wall and medial wall is restrained by cervical transverse, thyroid and adjacent muscle. The differences of Vs among walls of HP1 are the same with that of control group, but the values of Vs are lower, the Vs among walls both in HP2 and HP3 have no significant difference. The value of Vs decreases while the blood pressure increases, it indicates that the arteries elasticity and radial motional ability decrease with the increase of the blood pressure. The Smax and SRmax among walls of both case group and control group have no significant difference, the reason may be that Smax and SRmax reflect the deformation ability of local artery wall which have the same tissue composition with less influence of surrounding tissues. Comparing with the control group, the peak time of systolic strain and strain rate of common carotid arterial wall along the short axis are inconsistency. Smax and SRmax decrease with the increasing blood pressure, which indicates that the deformation ability decreases. Additional, the diastolic strain rate curve of case group has more positive and negative waves than that of control group, the reason may be the arterial compensation against high load, and it needs a further study. The influence of cardiac function towards velocity, strain and strain rate is less because there is no significance difference of EF between case group and control group. The commonly used parameters reflecting arteries elasticity are Ep,βand AC, while the velocity, strain and strain rate of artery wall detected by VVI reflect the biomechanics of elastic arteries and the deformation ability after left ventricular ejection. The Vs, Smax and SRmax obviously decrease with the increasing blood pressure, which can be the new indexes of abnormality of carotid artery elasticity in essential hypertension. The initial conclusion still needs support of large sample size because of the less cases of the study. The initial clinical study indicates that, VVI technology can show the change of common carotid artery elasticity in essential hypertension patients accurately, reveal the motion state of common carotid artery in different degree of essential hypertension patients to provide evidence for abnormality of large artery elasticity in essential hypertension. VVI technology has simple operation and accurate results, it will be a new method of evaluation of common carotid artery elasticity in essential hypertension.Come to the conclusion:(1)VVI technology can be used to observe the velocity, strain, and strain rate of common carotid arterial wall along the short axis in control group quantitatively, and supply new quantitative indexes for evaluation of common carotid artery wall elasticity(2)VVI technology can be used to observe the velocity, strain, and strain rate of common carotid arterial wall along the short axis in essential hypertension patients quantitatively, reveal the motion state of different degree and supply a new observation method of abnormality of large artery elasticity.(3)VVI technology has a higher quality requirement at two-dimension image, when the image is clear, the boundary of artery intima can be traced accurately. The accuracy of measurement value will be influenced by arrhythmia. And the detection to the artery elasticity is just based on a small sample without a standard reference index, and a further study is needed.(4)Compared with the traditional way to estimate the artery elasticity, VVI technology has no dependence on angle, less noise, direct display mode and better repeatability, uses the way of Acoustic collection,and can estimate the elastic change of artery wall in all directions, which find a new way for clinic and study work, maybe lead to a great effect to the diagnosis and cure of the cardiovascular disease with a wide development prospect. |
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