| Atherosclerosis (AS) is the most common and important one in the group of vascular diseases named as arteriosclerosis. The common feature for arteriosclerosis is that noninflammatory, retrogressive and hyperplasic changes happen to artery, which results in the affected vessel walls incrassated, hardened, lost elasticity and shrunk in lumen size. For AS, besides the above lesions, the affected artery also suffers from accumulation of lipidic and compound carbohydrate, bleeding, thrombosis, proliferation of fibrous tissue and calcareous deposition that starts with the intimae successively along with gradual deterioration and calcification of arterial media. The pathologic changes caused by AS involve mainly in the large elastic arteries such as the aortas and the middle muscular elastic arteries (mostly the coronary arteries and cerebral arteries, then the arteries of limbs and trunk, renal artery and mesenteric artery next). The affected arteries become less elastic, more brittle and easy to break; meanwhile, the arterial lumen turns narrow or even entirely off or develops into aneurysm, which may cause the entire circulatory system or individual organs dysfunctional. As per the statistic data released by American College of Cardiology (ACC) in 2004, AS is still the number one killer disease in America. Along with the development of economy and society, the blood vessel diseases have already ranked the top of all by incidence rate, and become a global heavy burden and a challenge to face in the new century. Long-term research has found out that carotid artery atherosclerosis (CAS) is approximately going on simultaneously along with atherosclerosis of aorta, but earlier than the occurrence of coronary atherosclerosis. CAS is significantly related to coronary artery disease (CAD) and ischemic cerebrovascular disease; meanwhile, the severity of CAS increases markedly along with the progress of coronary atherosclerosis. The functional lesion of endothelial cells is often the initiating step of AS occurrence, which is frequently accompanied with changes of arterial elastic function simultaneously. Therefore, it is of remarkable significance to research the early functional change of arterial elasticity for understanding the occurrence and progress of AS as well as the prevention and treatment of its complications.The reduction in arterial elasticity is the comprehensive manifestations of early lesions to vessel walls resulted from various cardiovascular and cerebrovascular risk factors, and it is also the specificity and sensitivity indicator of early vascular disease. Since it is hard to carry out directly morphological observation and quantitative estimation of arterial construction, a practical way is to measure the arterial expansibility or elasticity for the pathological changes of artery. Considering the fact that arterial elasticity is hard to measure directly, noninvasive methods are often used to quantify the arterial elasticity, of which the measured parameters include mainly internal diameter difference, pulse pressure, pulse wave velocity (PWV), reflected pressure wave 's argumentation index (AI) in the systolic phase, elasticity index of large arteries, elasticity index of small arteries, pulse wave 's attenuation parameter in the diastolic phase, concussion wave analysis of cuff internal pressure on measuring blood pressure, measurement of pulse pressure wave and ultrasonic Doppler measurement of arterial diameter's variation in response to pressure. Clinically, arterial PWV is always used as a noninvasive method for evaluation of arterial elasticity. However, along with the rapid development of science and technologies, it is reported that ultrasonic examination is used increasingly to evaluate the arterial elasticity. Peterson put forward the physical variables of elastic coefficient (Ep) and rigidity (β) in 1960, both of which can reflect blood vessel elasticity (or compliance) and are proven positively correlated with PWV. In recent years, ultrasonic technique has advanced to the level high enough to measure invasively the micro variation of arterial expansibility, peripheral stress and intima-media thickness (IMT), which are very helpful in acquiring important data of blood vessel like expansibility and compliance, and has become an important invasive measuring method for arterial functions. Along with the continual improvement of ultrasonic technique, such approaches as Tissue Doppler Imaging (TDI), Tissue Velocity Imaging (TVI) and Integrated Backscatter (IBS) have been used to evaluate arterial elasticity clinically. As proven by a great deal of research, carotid IMT measured with high resolution B-type ultrasonic imaging method has been widely recognized as a reliable indicator in diagnosis of CAS. And it is believed that IMT has a fairly good linear relationship with arterial elasticity. As mentioned above, arterial elasticity is a reliable indicator reflecting the early functional change of arterial buffer system. Echo -tracking (ET) technique is a brand new technique available in SSD 5500 Color Doppler Ultrasound Diagnostic Apparatus that is developed by Aloka Corporation. It is able to conduct real-time tracking and record of blood vessel frontal and rear walls' kinematic trace, compute automatically the variance of blood vessel's internal diameter in response to cardiac cycle, and display the result in form of curve. Its built-in digital image management system (e-DMS) is able to compute automatically such elastic indexes as Ep,β, arterial compliance (AC), AI and PWV, making it possible to evaluate artery vessels' elastic functions quickly and accurately.The first part of this paper focuses on animal experiments. It started with measuring health New Zealand white rabbits ' common carotid arteries for the ET indicators as normal reference values; then, the changes of the ET indicators in different AS modeling stages were observed. Finally, by connecting the pathological results with the changes of elastic indicators in the early stage of AS, it investigated the ET technique 's feasibility and accuracy in evaluation of early AS as well as the changes of elastic parameters along with AS progress. The second part is the applications of ET echo tracking in measuring the elastic indicators of health adults. It determines the range of normal values of health people's carotid elastic parameters and the influencing factors, which provide reference for the clinical diagnosis of AS. The third part is concentrated on the application of ET technique in evaluation of hypertensive (of various levels) 's carotid elastic functions. It is purposed to investigate the effects of systolic pressure, diastolic pressure and pulse pressure to arterial elasticity, and observe carotid IMT 's changes in hypertensive of various levels and correlation among elastic indicators. Part One:The Experimental Study on Blood Vessel E-tracking Technique in Quantitative Evaluation of Rabbits' Early Arteriosclerosis of Common Carotid ArteryObjective: Firstly, the high-resolution ultrasonic technique is adopted to check New Zealand white rabbits' construction of common carotid artery; and then ET technique is used to measure the elastic parameters. With reference to health rabbit's carotid elasticity data, the vessel wall construction and elastic changes are observed in different AS stages. Meanwhile, the elastic parameter changes of early AS are estimated on the basis of common carotid artery's pathologic changes. It is mainly purposed to discuss ET technique's feasibility and accuracy as well as elastic parameters' sensitivity in quantitative evaluation of rabbits' early AS.Method:39 four-month-old health New Zealand white rabbits were divided into four groups: 10 for control group, No.1 and No.2 modeling groups respectively, half male and half female; 9 for No.3 modeling group, 5 male and 4 female. ET technique and Aloka SSD 5500 SV Color Doppler Ultrasound Diagnostic Apparatus with built-in e-DMS were used to check the texture and ET indicators of rabbits' right-side common carotid artery under narcosis at 0 week, and then on the following morning, sample blood from each rabbit ear edge was taken for check of lipid level on fasting and drink-deprivation. Afterwards, the control group was fed with basal granulated feed while all the modeling groups were fed with high-fat granulated feed (containing 85% basal feed, 1% cholesterol, 10% yolk powder and 4% lard). The feeding amount was limited to 100g/day for each rabbit, twice each day at intervals of 12 hours without limit of drinking water. At the 4th weekend, repeated the above-mentioned ultrasonic sound and lipid level check to the control group and No.1 modeling group; at the 8th weekend, repeated the above-mentioned ultrasonic sound and lipid level check to the control group and No.2 modeling group; at the 12th weekend, repeated the above-mentioned ultrasonic sound and lipid level check to the control group and No.3 modeling group. No.1 and No.2 modeling group were killed at the 4th weekend and the 8th weekend respectively after the examination was completed. No.3 group and the control group were killed at the 12th weekend after the examination was over. Their common carotid arteries were taken out corresponding to the ultrasonically checked portions for pathologic analysis.Results:8 rabbits in each group were through the experiment, that is, 4 male and 4 female rabbits from each modeling group as well as 5 male and 3 female rabbits from the control group. (1) There was no evident difference between groups in weight, systolic pressure, diastolic pressure, lipid level, heart rate and ET indicators at 0 week (P > 0.05). (2) It was of no remarkable significance, though there were difference between the control group and the three modeling groups in weight, systolic pressure, diastolic pressure and heart rate at the 4th, 8th and 12th weekends respectively. (3) The blood cholesterol and triglyceride of all the three modeling groups were significantly increased in the 4th to 12th weeks comparing with their initial basic state in the 0 week or with the control group of the same period (P < 0. 001), but the difference between the three modeling groups was relatively small in between the 4th week and the 12th week. (4)Pathological Result:Of the control group, the common carotid arteries had smooth intima, well-arranged endothelial cells of uniform thickness, and smooth muscle cells arranged tightly into clear layers with less mesenchyme and no lipidosis. At the 4th weekend, slight trace of lipidosis were visible between the intima and the smooth muscle cells in the modeling groups while the cells of smooth muscle layer were arranged more loosely than that of the control group. At the 8th weekend, small amount of lipidosis and irregularly distributed foam cells were visible inside the intima in the modeling groups while the intercellular substances of smooth muscle layer increased and were arranged loosely. At the 12th weekend, it was observed that the vessel wall upswelled partially and lightly, the count of endothelial cells reduced slightly, lipid and foam cells become increased, incrassated and diffuse visibly inside the intima, some smooth muscle cells become atrophic, and the interstitial substance increased evidently between muscular fibers. (5) For Ep, it increased noticeably at the 4th weekend comparing with that at 0 week (P < 0.05), and the difference between the value at the 12th weekend and that at the 8th weekend as well as at 0 week respectively was significant statistically (P < 0.05 and 0.001 respectively). Forβ, it started to increase evidently at the 8th weekend comparing with that of the control group at 0 week (P <0.001), and the difference between the value at the 12th weekend and that at the 8th weekend as well as at 0 week respectively was significant statistically (P < 0.05 and 0.001 respectively). For PWV, it started to increase evidently at the 8th weekend comparing with that at 0 week (P < 0.05), and the difference between the value at the 12th weekend and that at 0 week was significant statistically (P < 0.001). For AC, Ds and Dd, there was noticeable change at the 12th weekend comparing with that at 0 week (P< 0.05).However, AI changed insignificantly all along. (6) Good positive correlation existed between Ep andβas well as between Ds and Dd (r= 0.6803 and 0.7539 respectively, both P < 0.001), betweenβand PWV as well as between Dd and PWV (r=0.5575 and 0.5405 respectively, both P < 0.05); negative correlation existed between AC and PWV (r=-0.5442, P < 0.05). Conclusion: ET technique is accurate and reliable as a noninvasive examination means in evaluation of the reduction of arterial elasticity for early AS, which, hopefully to be recognized as a diagnosis method of AS, has extensive application prospects.Part Two:The Study on Blood Vessel E-tracking Technique in Evaluation of Adult Common Carotid Elasticity and Influencing FactorsObjective:Since it has been proven through animal experiments that ET technique is able to evaluate the changes of arterial elasticity for early AS, it is imperative to study the normal reference values of elastic parameters. This study is purposed to research ET technique's application in quantitative evaluation of health volunteers' carotid elastic parameters and the influencing factors as well as to determine the normal ranges of relevant parameters, so as to provide reference for clinical diagnosis of AS.Method:180 health volunteers, whose ages were from 20 to 76 with the average age equal to 51.2±21.4, were divided into 6 age groups, that is, 20s Group, 30s Group, 40s Group, 50s Group, 60s Group and 70s Group. Each group contained 30 people, half male and half female. Blood vessel ET technique was used to acquire the three indicators of both common carotid arteries, namely, Ep,βand AC. Then an analysis was made on the relationship between these indicators and age, sex, IMT, heart rate as well as blood pressure.Results:(1) Age was positively correlated with Ep andβnoticeably (r= 0.704 and 0.653 respectively, both P< 0.001), but negatively correlated with AC obviously (r=-0.5878, P< 0.01); both systolic pressure and pulse pressure were positively correlated with Ep noticeably (r= 0.613 and 0.609 respectively, both P< 0.001); the correlation between sex, heart rate, diastolic pressure or IMT and Ep,βand AC was insignificant. (2) Of the age groups younger than 50, both Ep andβincreased progressively along with the age growing (all P< 0.001), but AC reduced (all P< 0.001). However, of the age groups older than 40, the parameter variation was little between age groups, and no significant difference comparing with the 40s Group. (3) The fluctuation ranges of Ep,βand AC were 118.68±34.25, 8.70±2.55 and 0.73±0.26 respectively for volunteers who were not younger than 40, but they varied along with age difference for those who were younger than 40.Conclusion: ET technique is able to measure the functional parameters of carotid elasticity accurately, which provides clinically a reliable new means in quantitative evaluation of carotid elasticity.Part Three:The Clinical Study on Blood Vessel E-tracking Technique in Quantitative Evaluation of Hypertensive 's Common Carotid Elasticity Objective:It is purposed, on the basis of Part 2's investigation, to research the clinical application significance of high-resolution ultrasonoscopy plus ET technique in quantitative evaluation of hypertensive 's common carotid elasticity in addition to analysis of blood pressure's correlation with elastic indicators.Method: 60 patients of primary hypertension, 34 male and 26 female who were 45 to 68 years old with the average age of 56.17±8.78, were divided into three groups, namely Level-1 Group, Level-2 Group and Level-3 Group. Each group contained 20 patients. Meanwhile, 20 health volunteers,34 male and 26 female who were 45 to 67 years old with the average age of 54.77±9.55 were arranged as the normal control group. A high-frequency linear array probe was used for measuring both common carotid IMT while ET technique was adopted for the three indicators of both common carotid arteries, namely, Ep,βand AC. Finally, an analysis was made for the relationship between these indicators and blood pressure.Results:(1) The differences of systolic pressure, diastolic pressure, pulse pressure and mean arterial pressure between groups were statistically significant (P<0.05 and 0.001 respectively). (2) Ep,βand IMT increased gradually along with the elevation of blood pressure, but AC decreased. The differences between groups were statistically significant (P< 0.05 and 0.001 respectively). For Ds and Dd, there was no obvious change between the Level-1 Group and the control group, but it indicated significant increase in the Level-2 Group and the Level-3 Group comparing with the control group (P <0.01). (3) Of the patients suffering from high blood pressure that were investigated here, Ep,β, Ds, Dd and IMT were positively correlated with systolic pressure, diastolic pressure, pulse pressure and mean arterial pressure significantly (P <0.05, 0.01 and 0.001 respectively); AC was negatively correlated with systolic pressure, diastolic pressure, pulse pressure and mean arterial pressure significantly (P <0.05, 0.01 and 0.001 respectively); and the correlation of Ep,β, Ds, Dd and IMT with heart rate was insignificant. (4) Ep andβwas positively correlated with IMT significantly (r=0.5953 and 0.7757 respectively, both P< 0.001), but negatively correlated with AC significantly (r=-0.5237, P< 0.001). Ds and Dd were positively correlated with IMT (r= 0.2750 and 0.2903 respectively, P< 0.05).Conclusion:The common carotid IMT increases progressively along with the gradual elevation of blood pressure, but the arterial elasticity reduced gradually. It is concluded that ET technique is accurate in quantitative evaluation of common carotid elasticity. |
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