The Clinic Value Of Carotid Intima-media Inhomogeneity In Cardiovascular Risk Stratification And Coronary Heart Disease

The world health report in2005suggested that the worldwide overall mortality of cardio-cerebral vascular diseases was calculated at218/100,000person years. An epidemiological study indicates that diseases of the heart (mortality rate was22.5%) and cerebrovascular disease (mortality rate was21.3%) are the leading causes of death in the Chinese population of adults40years of age and older. The prevalence of cardio-cerebral vascular diseases was appeared to be increasing, about290million patients together, and every10seconds a person died from it. Atherosclerosis had become an important public health problem.Various techniques for atherosclerosis have been employed, including digital subtraction angiography (DSA), magnetic resonance angiography (MRA), computed tomography angiography (CTA), ultrasound and ankle brachial index (ABI), et al. DSA is the gold standard in the diagnosis of artery stenosis. MRA and CTA also can be used to adequately evaluate artery stenosis. But they are invasive, time consuming and expensive. ABI is a useful clinical test to assess the arterial blood supply to the foot, but the hardening and incompressibility of arteries can affect the accuracy of it. Ultrasound is a noninvasive, low-cost and reproducible that it appears to be widely clinical application.Noninvasive assessment of carotid artery intima-media thickness (CIMT) is independently associated with both the presence of coronary artery disease and the occurrence of a cardiovascular event. Hazard rate ratios (HRRs) per1SD CCA-IMT increase were1.43[95%CI:1.35to1.51] for myocardial infarction (M1),1.47[95%CI:1.35to1.60] for stroke, and1.45[95%CI:1.38to1.52] for M1, stroke or death (all P<0.0001). However, the increase in the mean and maximum IMT represents only one part of the structural atherosclerotic alterations of the arterial wall visible in ultrasound images. Carotid intima-media inhomogeneity (CIMI) is the variations in IMT. It can measurement the changes as granulations of the IM layer, e.g.①CIMI can differentiate diffuse intimal thickening from fibrous plaque formation. It is still unknown whether these sits of diffuse intimal thickening may progress to advanced atherosclerotic lesions.②CIMI can differentiate a single early plaque with otherwise normal IMT from a complicated advanced lesion with multiple plaques and ulcerations. In addition, a recent epidemiological study has revealed and the angiographic inhomogeneity of carotid arteries was closely associated with atherosclerosis. Due to technical limitations, few investigations have been performed to evaluate the carotid artery IMT inhomogeneity using ultrasonography. The purpose of the study was to adapt the program to the measurement intima-media inhomogeneity (CIMI), and investigate the clinic value of it in cardiovascular risk stratification and coronary heart disease. The present study was divided into three parts as follows.Part1Age-related changes in carotid Intima-media inhomogeneity assessed by ultrasoundThe aim of this part was to evaluate the structural and elastic changes of the carotid artery in healthy volunteers. They were divided into three groups by age. A younger group (19-45year-old), a middle age group (46-64year-old) and an elder group (≥65year-old). CIMI, CIMT were measured by an automatic measuring system. Elastic index such as stiffness (β), pulse wave velocity (PWV) were measured by Echo-Tracking. Results①There were no statistically significant difference among three groups of gender, smoking history, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), triglycerides (TG), total cholesterol (TC), High-density lipoprotein (HDL), Low-density lipoprotein (LDL), fasting plasma glucose (FPG).(all P>0.05)②Arterial structures and stiffness:compared with the younger group, The incidence of plaque, CIMT,β, PWV in middle age and elder group and Ln (CIMI) in elder group were insignificantly increased (P<0.01). In comparison with the middle age group, the incidence of plaque, CIMT were insignificantly increased (P<0.01).③Correlation analysis showed that the age was correlated with Ln (CIMI),β, PWV, CIMT (r=0.322,0.429,0.443,0.585, P<0.01). The incidence of plaque was correlated with Ln (CIMI), CIMT, PWV, β (r=0.576,0.573,0.354,0.329, P<0.01). The smoking history was correlated with CIMT, Ln (CIMI)(r=0.358,0.354, P<0.01). Ln (CIMI) was correlated with CIMT, PWV (r=0.690,0.222, P<0.05).④The reproducibility was good as shown by Bland-Altman plot. All of the values lying within1.96SD.Part2The clinic value of carotid intima-media inhomogeneity in cardiovascular risk stratificationAccording to the Framingham cardiovascular risk scores, all patients were divided into three groups:the low risk, the intermediate risk and the high risk group. And we also classified the subjects by median according to the value of CIMI. CIMI, CIMT were measured by an automatic measuring system. Elastic index such as stiffness (β), pulse wave velocity (PWV) were measured by Echo-Tracking. These indexes were compared among three groups. Factors correlated with CIMI were evaluated. Results①There were significant differences of age, gender, smoking history, The incidence of hypertension, hyperlipidemia, obesity, cardiovascular events, systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting plasma glucose (FPG) among three groups (all P<0.05). And the incidence of diabetes was no significant difference among three groups (P>0.05).②Arterial structures and stiffness:compared with the low risk group, The incidence of plaque, CIMT, CIMI, β, PWV in the intermediate risk and the high risk group were insignificantly increased (P<0.01). In comparison with the intermediate risk group, the incidence of plaque, CIMT, CIMI in high risk group were insignificantly increased (P<0.01). β, PWV in high risk group were no significant difference (P>0.05).③According to the value of CIMI, we classified the subjects by median:Median1group (CIMI>0.0691mm) and median2group (CIMI≤0.0691mm). Compared with the median1group, the age, Incidence of hypertension, cardiovascular events and plaque, smoking history were significantly higher in the median2group (P<0.01). The number of cardiovascular risk factors was significantly increased in the median2group (P<0.05). There were no significant differences of the incidence of diabetes, hyperlipidemia, obesity between two groups (P>0.05).④Correlation analysis showed that CIMI was correlated with age, the incidence of plaque, cardiovascular events, hypertension, smoking history, hyperlipidemia, fasting plasma glucose (r=0.443,0.428,0.417,0.321,0.267,0.207,0.140, P<0.05). CIMI had a strong correlation with CIMT (r=0.728, P<0.01). And it had weak correlations with β, PWV (r=0.304,0.330, P<0.01). In multivariable stepwise regression analysis, age, the incidence of cardiovascular events, hyperlipidemia and smoking history were factors independently correlated with CIMI. Part3The predictive value for coronary heart disease by carotid intima-media inhomogeneityAccording to the results of coronary angiography, the subjects were divided into the normal control group and coronary artery disease group. CIMI, CIMT were measured by an automatic measuring system. Elastic index such as stiffness0), pulse wave velocity (PWV) were measured by Echo-Tracking. The sensitivity and specificity of CIMI for detection of coronary artery disease were performance by receiver operating characteristic (ROC) curve. Results①There were no statistically significant difference between the two groups of age, gender, systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), triglycerides (TG), total cholesterol (TC), High-density lipoprotein (HDL), Low-density lipoprotein (LDL), fasting plasma glucose (FPG).(all P>0.05)②Compared with the normal control group, the incidence of plaque, CIMT, CIMI in the coronary artery disease group were insignificantly increased (P<0.01). There were no significant differences of β、PWV between the two groups (P>0.05).③Pre1:CIMI and CIMT combined; Pre2:CIMI, CIMT, β and PWV combined. The area of under the ROC curve corresponded to Pre2, CIMI, Pre1, CIMT were0.773,0.763,0.752,0.691, respectively (P<0.01). The area of under the ROC curve corresponded to PWV, β were0.623,0.591, respectively (P>0.05). The cutoff of CIMI and CIMT was0.0721mm and0.7081mm, and then the sensitivity and specificity for detection of coronary artery disease were78.8%,68.3%and63.6%,61%, respectively. ConclusionsIn this study, our conclusions are as follows:1. CIMI is thought to reflect the atherosclerotic wall process in addition to the intima-media thickness measurement. It has a lower association with age compared with CIMT, and helps to discriminate among individuals presumed to be the low risk, the intermediate risk and the high risk of coronary artery disease.2. Age, the incidence of cardiovascular events, hyperlipidemia and smoking history were factors independently correlated with CIMI.3. CIMI has a valuable application for assessment of coronary artery disease.4. More than20years old, the thickness of the walls of carotid artery increases with age. And more than64years old, the incidence of plaque, the intima-media thickness and inhomogeneity, stiffness increases with age.5. According to traditional risk factors present, the incidence of plaque, the intima-media thickness and inhomogeneity and artery stiffness in the intermediate risk subjects increase comparing with the low risk one. The intima-media thickness and inhomogeneity in the high risk subjects increase comparing with the intermediate risk subjects. But the stiffness was no significantly increase.