1.Both Pressure Gradient And Plaque Echogenicity Influence The Stability Of Internal Carotid Plaques 2.A Long Term Follow-up Study For Carotid Endarterectomy Of Symptomatic Carotid Stenosis

OBJECTIVES Intracranial artery embolism is one of the major mechanisms of ischemic stroke in patients with carotid atherosclerosis.Carotid atherosclerosis plaques cause 8%to 29%of all ischemic strokes.The aim of treatment for patients with carotid stenotic disease lies in decreasing the risk of disabling stroke or stroke-related death as consequences of thromboembolism.Nowadays,more specialists agree that only the degree of carotid stenosis is not sufficient to identify vulnerable patients at high risk to develop an acute ischemic stroke.Operating CEA on asymptomatic patients with severe carotid stenosis to prevent stroke demonstrates effectiveness but with less cost-effective.Study has demonstrated that in asymptomatic patients with severe carotid stenoses,85 operations were needed to prevent a single ischemic stroke.Therefore,it is an important topic how to identify vulnerable plaques with sever carotid stenosis that prone to rupture leading to ischemic stroke,so that we can prevent ischemic stroke effectively and accurately.Advanced ultrasound as a noninvasive method can diagnose hemodynamic compromise of carotid stenosis,as well as the characteristic of carotid plaques.Approximate 80%of patients in North America undergo CEA depending on US examination as the only preoperative imaging study.We design this longitudinal observational study to investigate the following objectives:(1) higher velocity at narrowing carotid has an effect on blood pressure gradient;(2) echogenicity of plaque influences the rate of ischemic stroke;(3) blood pressure gradient and plaque echogenicity influence the stability of carotid plaques.METHODS From January 2004 to December 2008,1408 patients with 2816 total carotid arteries under ultrasound screening,were analyzed in hemodynamic,echogenic,and pathological characteristics of carotid plaques,respectively.Definition of terminology is made for risk factors and neurologic symptoms,including:Hypertension,Diabetes mellitus, Hyperlipidemia,Smoking,Cardiac disease,Peripheral artery disease, Stroke,and TIA.The primary endpoints were defined as:(1) progressive asymptomatic stenosis progressed to occlusion;(2) occurrence of stroke;(3) Death by any cause in follow-up.B-mode,color flow images,and spectrum waveform were acquired for imaging of the carotid bifurcation and ICA three different views (acoustic windows) were used with the anterior,lateral and posterolateral.In each case,Color Doppler Flow Imaging(CDFI) and spectrum waveform techniques were used to estimate the degree of stenosis.Ultrasound criteria for ICA occlusion included the lack of color flow in the ICA and no signal available in spectrum waveform analysis,and detection of a diastolic flow towards zero in the common carotid artery.Echogenic characterization of plaques is classified into 3 different groups:(1) hypoechogenic plaque is fatty(soft) plaque;(2) mixed echogenic plaque without shadow is approximately the equal ratio of fatty and calcification in plaque;(3) hyperechogenic with shadow is calcified plaque.The blood pressure decreases across carotid stenosis as blood velocity increase.Pressure gradient is calculated by using modified form of Bernoulli's equation:Δp=o.5 p V~2,unit in this form is dynes.Dynes is converted to mmHg,theΔP=4V~2;unit ofΔP in this form is mmHg.Statistical analysis Explore analysis was hired to investigate the pressure gradient of subtypes of stenosis.The relationships between subtype of the ICA stenosis and ICA plaque echogenicity were determined by correlation analysis.Multivariate logistic regression analysis was used to identify the vascular risk factors.The KaplanMeier survival curve was used to calculate the death rate of different carotid stenosis group.RESULTS 174 positive patients are identified with carotid hemodynamic abnormality(＞60%).Among 348 carotid arteries,117 male,57 female;mean age:74.8 years,range:52 years,from 43 to 95;97 carotid in＜60%,143 carotid in 60%-79%,62 in 80%-99%,46 in occlusion.According to modified form of Bernoulli' s equation:ΔP=4V~2,unit in this form is mmHg.The calculated results of the pressure drop across at＜60%stenosis were 3.13±2.09 mmHg in right carotid,3.50±2.03 mmHg in left carotid.The 60%-79%stenosis were 11.55±5.97 mmHg in right carotid and 11.58±5.01mmHg in left carotid. The 80%-99%stenosis were 51.73±35.15 in right carotid and 48.83±28.58 in left carotid.There were significant diffenrence between subtype of pressure gradient.The result of echogenicity of plaques demonstrated that hypoechogenic plaque had much more positive correlation with cerebrovascular events than mixed and hyperechogenic plaques.CONCLUSIONS and SIGNIFICANCES In symptomatic and asymptomatic severe carotid stenosis(80%-99%),the flow velocity is increased in the same situation.However during the long term follow-up with ultrasound for asymptomatic severe carotid stenosis(80%-99%),the positive patients can survive for several years without symptoms of stroke and TIA.If the pressure gradient is a critical factor to rupture the plaques,the symptoms should emerge within a short period under extremes values.The explanation of long-term asymptomatic survival is that the extreme situation can not change a stable plaque into a unstable plaque.Therefore,the internal characteristics of a plaque are the critical factor to rupture plaques causing symptoms.By analyzing the property of plaque echogenicity in different group,the hypoechogenic plaques in severe carotid stenosis group were accompanied by higher frequent neurologic symptoms than mixed and hyperechogenic plaques in the same carotid stenosis.This result proved further evidence that the internal property of plaques were the critical factor to determine the plaque stability.In summary,the result of this study had demonstrated that higher flow velocity which was caused by carotid stenosis produced blood pressure gradient at carotid stenosis.This pressure gradient influence the plaque stability,however it was not the dominant factor in causing neurologic symptoms.The internal characteristic rather than the external factors of plaque should be the dominant determinant to rupture plaque which associates with ischemic stroke and related symptoms.The echogenic plaque property has demonstrated that hypoechogenic plaquend are more prone to cause cerebral symptoms than mixed echogenic plaque and hyperechogenic calcified plaque. Therefore,it must be bear in mind that carotid ultrasound examination should investigate both the internal characteristic of plaque and external hemodynamic abnomal at the narrowest stenosis site. OBJECTIVES Carotid endarterectomy(CEA) is supported by clinical evidence (Class 1 and Level A) as the standard treatment of severe carotid stenosis in symptomatic patients.Although,it is partly replaced by popular Carotid Artery Stenting(CAS) recently,however,CEA is still regarded as a golden standard procedure in reducing the long-term risk of stroke and mortality due to severe carotid stenosis in symptomatic patients.So far,prospective,randomized clinical trials(RCTs) have compared the effect of Carotid Artery Stenting(CAS) and Carotid Endarterectomy(CEA).The results demonstrated that adoption of Carotid Artery Stenting(CAS) with the hope of decreasing postoperative stroke or death rate is not warranted at current time.The purpose of this study is to analyze long-term stroke-free survival and early restenosis survival in a consecutive series of patients who underwent CEA for symptomatic carotid disease.METHODS Patient data were retrospectively collected for all patients who underwent conventional CEA with primary closure or patch for symptomatic severe carotid disease performed by a vascular surgeon.All included CEAs were performed from 1996 to 1998 in 102 patients.All CEA were performed under general anesthesia. Most patients had neurological follow-up and duplex ultrasound at 1,3,6,and 12 months,and biannually thereafter.Kaplan-Meier curve is used to analyses long-term free-stroke survival and early restenosis survival.Probability values＜0.05 are considered statistically significant.RESULTS Perioperative neurologic complications included 3 transient ischemic attacks(TIAs)(2.9%),3 nondisabling strokes(2.9%).There was one 30-day death from this study(0.9%),7 patients with late death.Long term free-stroke survival rate was 90%and 65.7%at 5 and 12 years,respectively.Kaplan-Meier curve was used for every risk factor,but no significant difference was obtained.CONCLUSIONS Conventional CEA with primary closure proved safe and effective outcome in a series of patients with symptomatic severe carotid disease representing the typical population of daily clinical practice.Long term free-stroke survival rate was 90%and 65.7%at 5 and 12 years,respectively.It is not inferior to previous studies,which showed the accumulate stroke rate of symptomatic carotid stenosis without surgical intervention with 30%at 5 years.The result of this study demonstrated that it could prevented 20%ischemic stroke approximately.In this study,conventional CEA proved safe and effective long term effect on preventing stroke under experienced vascular surgeon.Carotid endarterectomy,as an effective,affordable,widely applicable treatments should be recommended for symptomatic patients.