| BackgroundAtrial fibrillation (AF) is one of the most common cardiac arrhythmia, of which the biggest hazard is its thromboembolic complication. According to epidemiological studies, the prevalence rate of stroke in hospitalized patients of AF in our nation is up to24.8%, which is far above that in population without AF. What is more, stroke caused by AF are much pernicious and its lethality is two times higher than stroke caused by reasons other than AF. Therefore, it is of great importance to find methods that can early detect and prevent the risk factors of thromboembolism in patients with AF. Previous studies have proved that the main source of embolus of ischemic stroke in AF is left atrial thrombus, and90%of which rest in the left atrial appendage. At the same time, as the major fundamental causes of non-valvular atrial fibrillation (NVAF) are also the major risk factors of atherosclerosis, such as hypertension, diabetes, coronary heart disease and advanced age, patients with NVAF may suffer from aortic and peripheral atherosclerosis simultaneously as well. In the general population, aortic and carotid atherosclerotic plaques, as source of20%～25%of cerebral emboli, were documented to be strong and independent risk factors for ischemic stroke. Furthermore, the ultrasonic study of SPAFIII has indicated that aortic atherosclerotic plaque was an independent risk factor for ischemic stroke in patients with AF. Nevertheless, the contributions of carotid plaque to ischemic stroke in patients with AF are not quite clear.Prevention of stroke is an important part of atrial fibrillation treatment and stroke risk stratification in patients with atrial fibrillation would greatly help the clinical individualized treatment. Methods currently used in clinical practice to evaluate the risk of stroke are the CHADS2score system put forward by the2006AF guidelines of ACC/AHA/ESC and the CHA2DS2-VASc scoring system proposed by ESC in2010AF guidelines. There have been several studies both in our nation and abroad that have confirmed that CHADS2scoring system can effectively assess the risk of stroke in patients with atrial fibrillation, as well as improve the standardization of anticoagulant therapy in patients with AF. Existing research in our nation and abroad also have proved that CHADS2score has a strong signal effect for left atrial origined cardiovascular events in patients with atrial fibrillation. But for atherosclerosis plaque source embolism, the forecast effect of stroke risk stratification is not clear.Atherosclerosis is considered to be a systemic vascular lesion, which is caused by the same pathologic process involving in different vascular beds. Peripheral artery atherosclerosis and cerebral atherosclerosis enjoy the same pathologic basis and risk factors. Subsequently, carotid artery can be used as an indirect reflection of the extent of systemic atherosclerosis. Using doppler ultrasound detection of carotid artery atherosclerosis plaque morphology, IMT and hemodynamic changes, one can visually and dynamically evaluate the structure and function of carotid artery, and predict future cardiovascular events. Velocity vector imaging (VVI) technology is a new risen technology in recent years for determination of myocardial and vascular wall motion, which can be used in detecting the elasticity characteristics, vessel wall elasticity and elastic-derived parameters of common carotid. By combining VVI with the traditional ultrasonic testing indicators, one can more comprehensively evaluate and understand the elasticity and mechanism factors of arteries.Objectives1. Investigate the characteristics of atherosclerotic lesions in patients with AF using the technology of Doppler Ultrasound;2. Investigate the mechanic characteristics and movement synchronization characteristics of the long axis of the common carotid artery in patients with AF using velocity vector imaging(VVI);3. Explore whether carotid atherosclerosis in patient of AF is an independent risk factor of ischemic stroke; 4. Explore the relationships between CHADS2score, CHA2DS2-VASc score and carotid atherosclerosis and its significance.Subjects and methods1. A total of159subjects were enrolled, divided into the following three groups:(1) The control group consists50subjects(22males and28females, aged38-76,55.98±7.19in average), all of whom are health examinees and health volunteers in Qilu Hospital of Shandong university. There is no abnormality found during detailed history collection, physical examination, routine12lead ECG examination, routine echocardiography examination, blood biochemical examination, hypertension, diabetes, kidney disease, arrhythmia, heart failure, and organic heart disease excluded.(2)The paroxysmal atrial fibrillation group consists59subjects(22males and37females, aged30-75,58.32±10.18in average). Cases that can exclude organic heart disease by detailed history collection, physical examination, conventional echocardiography and have the routine12lead electrocardiogram (ECG) or (and)24h dynamic electrocardiogram examination confirmed for paroxysmal atrial fibrillation were included in this group.(3) The persistent atrial fibrillation group consists50subjects(18males and32females, aged25-78,59.30±8.94in average), Cases that can exclude organic heart disease by detailed history collection, physical examination, conventional echocardiography and have the routine12lead electrocardiogram (ECG) or (and)24h dynamic electrocardiogram examination confirmed for persistent atrial fibrillation were included in this group.2. Instruments and equipments:Adopting the Siemens Sequoia512color Doppler ultrasonic diagnostic apparatus,15L8high frequency transducers (8.0～14.0MHz frequency). VVI offline analysis software (syngo US workplace) is provided by Siemens Company.3. Research methods:All participants have take full physical examinations; including height, weight, waist circumference, hip circumference, blood pressure and heart rate, etc. Full medical history, family history and medication history is documented. After overnight fasting12to14hours, extract fasting venous blood the next morning to determinate fasting blood glucose (FBG), triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL) and high density lipoprotein cholesterol (HDL). Participants lie down for application of carotid artery ultrasound measurement of carotid artery athermanous plaque and carotid artery IMT, carotid artery diameter and carotid artery blood flow velocity.Turn on VVI mode to storage two-dimensional dynamic real-time gray-scale images of long axis common carotid artery for future offline analysis.4. Statistical analysis:Statistical analysis was performed by SPSS18.0software package, whereas P<0.05reveals statistically significant. Continuous data are given as X±SD, comparison of which was performed by independent-sample t-test. Discrete variables were expressed as absolute frequencies and percentages when appropriate and analyzed by chi-square test. Binary logistic regression analysis was performed to screen possible independent risk factors for carotid atherosclerotic plaque. Parameter comparison between groups using one-way ANOVA, and comparing two groups using LSD-t test, Pearson variables linear correlation analysis and multiple factor linear stepwise regression analysis is preformed, and screening of risk factors using the unconditional Logistic regression model, calculate the OR values and95%confidence interval.Result1. Compared with control group, the paroxysmal atrial fibrillation group’s clinical data (including systolic blood pressure, pulse pressure, waist-to-hip ratio, history of drinking, hypertension, diabetes, coronary atherosclerosis heart disease, hyperlipidemia) were significantly increased (P<0.05-0.001); Carotid ultrasound indexes of plaque index, average IMT, Ds, Dd, AC are also increased significantly, while at the same time Vs, Vd reduced significantly; For indexes of VVI, those reflecting the long axis longitudinal motion index of the carotid artery (including PvS, PvD, PsS, PsD, PsrS, PsrD, PdS, PdD and tLoD) were significantly lower, and at the same time indicator of PvD (reflect the carotid long axial radial movement) is also significantly lower.2. Compared with normal control group, the persistent atrial fibrillation group’s clinical data (including systolic blood pressure, pulse pressure, heart rate, waist-to-hip ratio, smoking history, drinking history, history of coronary atherosclerotic heart disease, stroke) were significantly increased, and average IMT, maximum IMT, plaque index, Ds, Dd, AC, Ep and Ep*increased significantly, while at the same time Vs, Vd reduced significantly; Compared with the paroxysmal atrial fibrillation group, persistent AF group’s heart rate and stroke history were significantly higher, plaque index significantly increased, and RI significantly reduced.3. Compared with control group, the paroxysmal atrial fibrillation group; Compared with control group, the persistent AF group’s indexes reflect the carotid long axis longitudinal motion (including PvS, PvD, PsS, PsD, PsrS, PsrD, PdS, PdD and tLoD) were significantly lower, while at the same time reflect the carotid long axial radial movement indicators PvS, PdS and PdD also significantly lower; paroxysmal and persistent AF group did not show any statistical differences between each index.4. Compared with the control group, the diastolic peak displacement of paroxysmal atrial fibrillation group was obviously increased; The rest of the synchronicity index did not show any statistical differences between groups.5. Ischemic cerebral stroke events:Between the109cases of atrial fibrillation in patients,15cases were confirmed by craniocerebral CT or magnetic resonance imaging (MRI) for ischemic stroke patients accounted for14%of all patients with atrial fibrillation. Compared with carotid artery without plaque group, ischemic stroke incidence of carotid artery plaque group was obviously increased.6. Compared with control group, the paroxysmal AF and persistent AF groups’ CHADS2score and CHA2DS2-VASc scores were significantly higher; CHADS2score and CHA2DS2-VASc score between paroxysmal AF and persistent AF group did not reach statistical difference.7. CHADS2score is related to average IMT, maximum IMT, plaque index, Ds, Dd, Vs, Vd, DC, AC, Ep and Ep*, which reflect carotid artery structure and function. PvS, PsD, PsrS, PdD, tLoD, which reflect the carotid elasticity of long axis movement and TPvS, TPsrS, which reflect the carotid artery long axis movement synchronization indexes are also related to it. 8. CHA2DS2-VASc score is related to average IMT, maximum IMT, plaque index, Ds, Dd, Vs, Vd, DC, AC, Ep and Ep*, the indexes related to carotid artery structure and function, including PvS, PsD, PsrS, PdD, tLoD, which reflect the carotid elasticity of long axis movement and TPvS, TPsrS, which reflect the carotid artery long axis movement synchronization index are also related to it.9. When using Logistic regression to screen risk factors for plaque index increase, CHADS2score, sex, and heart rate went into the regression equation, indicate that when CHADS2score is high, male with the rapid heart rate is susceptible to carotid artery plaque index increase.10. When using Logistic regression to screen risk factors of IMT thickening, CHADS2score, total cholesterol and LDL-C into the regression equation, indicate that when CHADS2score is high, ones with higher total cholesterol and LDL-C is susceptible to IMT thickening increase.11. Multiple linear regression results are as follows: Mean IMT=Age×.004+WHR×0.358+CHADS2score×0.022; Max IMT=Age×0.005+CHADS2score×0.040+WHR×0.438; DC=CHADS2scpre×0.022-SBP×0.002+DBP×0.002; AC=SBP×0.096-DBP×0.102+CHADS2score×0.383.Shown the above variables have linear dependence relationships with CHADS2score.Conclusion1. The structure and function of carotid artery in patients with atrial fibrillation have changed significantly, which mainly presents as increased plaque index, reduced IMT, artery diameter expansion, increased flexibility and stiffness and decreased blood flow velocity;2. In patients with atrial fibrillation, thickening of carotid artery intimae is a risk factor for ischemic stroke onset, which reveals that atherosclerosis complicated by atrial fibrillation may have important effects on the happening of ischemic stroke, which could be a guidance for clinical anticoagulant therapy of atrial fibrillation;3. The CHADS2score and CHA2DS2-VASc score was correlated with parameters of carotid ultrasound, shows that atrial fibrillation stroke risk stratification can reflect the degree of carotid artery structure and function damaging;4. Velocity vector imaging can be used in assessment of mechanism characteristics of carotid artery wall in patients with atrial fibrillation; its clinical significance is worth future research. |
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