A Study On Hemodynamic Characteristics Of Middle Cerebral Artery Stenosis And Its Correlation With Plaque Vulnerability

Part?Application of High-Resolution Magnetic Resonance Imaging in vulnerable plaques of Cerebral Artery Atherosclerotic StenosisObjective: Recently,high-resolution magnetic resonance(HR-MRI)is available to identify the carotid atherosclerotic vulnerable plaques accurately,which show an agreement with the histopathological description.Our aim was to detect plaque and evaluate signal intensity in intracranial atherosclerotic stenosis(ICAS)on contrast-enhanced high-resolution MR imaging,and to discuss risk factors of accelerating these plaques to strengthen.Meanwhile,the relationship between different signal intensity of plaques and symptomatic middle cerebral artery stenosis should be analysed.Furthermore,to access the judgment of HR-MRI in identifying plaque vulnerability,and to predict the clinical utility in ischemic events would be necessary.Methods: All patients with local atherosclerotic stenosis in middle cerebral artery(MCA-M1)diagnosed by 3-dimension digital subtraction angiography(DSA)from June in 2014 to December in 2015 were included in this study retrospectively.The signal intensity of atherosclerotic plaque should be evaluated by HR-MRI.We collected the patient's clinical and imaging information that the scanning sequence including T1 weighted fast spin echo(T1WI-FSE)?T2 weighted fast spin echo(T2WI-FSE)? short time inversion recovery(STIR)and contrast-enhanced T1 weighted imaging(T1WI+C).According to the signal intensity of atherosclerotic plaque by HR MRI findings,all patients could be divided into the enhancement group(n=30)and the non-enhancement group(n=12).The stenosis degree in M1 segment was measured by “the golden standard” DSA.The baseline target such as age,sex,degree of artery stenosis,mean arterial pressure(MAP)and some atherosclerosis related medical histories of hypertension,diabetes and hyperlipemia(HLP)were collected and compared between the two groups,and the enhancement ratio of atherosclerotic plaque in ICAS were analyzed in these groups.Results: A total of 42 patients of MCA stenosis that ages ranging from 30 to 79 were admitted in this study.There were 30 patients in the enhancement group(19men and 11women),which ages were 56.5(49.75,65.25)ys,and 12 patients in the non-enhancement group(7men and 5women),which ages were 56(51.25,62.75)ys.There were no statistically significant differences between the two groups in the parameters such as age,sex,mean arterial pressure(MAP)and some atherosclerosis related medical histories of hypertension,diabetes and hyperlipemia(HLP)(P>0.05).However,the degree of artery stenosis in the enhancement group was much more severe than that in non-enhancement group,and the statistical differences between the two groups was essential[57%(51.75,63.5)% VS 49%(43,56.5)%,U=103.5,P=0.032].The clinical ischemic events rate in the interesting artery between the two groups was shown that there were significant statistical discrepancies between the two groups.The rate of ischemic events in the enhancement group was higher than that in non-enhancement group,and the statistical differences between the two groups was significant(76.7% VS 25%,?2=7.635,P=0.006).Conclusion: HR MRI can reflect the characteristics of intracranial atherosclerotic stenosis plaque and the signal intensity of atherosclerotic plaque has an association with the degree of artery stenosis.Compared with the non-enhancement plaque ones,the rate of ischemic stroke in patients with the strengthen plaque are much higher.Part? Analysis of Hemodynamic Risk Factors of Plaque Vulnerability in Middle Cerebral Artery Atherosclerotic StenosisObjective: Atherosclerotic vulnerable plaque is a major risk factor for clinical ischemic events.Hemodynamic factors plays a very important role in the formation and progress of atherosclerotic plaque.Untill now,the relationship between hemodynamics and unstable plaque has not clear.We aimed to observe the hemodynamic parameter distribution in different locations near atherosclerotic plaques of intracranial atherosclerotic stenosis(ICAS)and investigate the impact of hemodynamics of ICAS revealed by computational fluid dynamics(CFD)models on the atherosclerotic plaque feature by high-resolution magnetic resonance imaging(HR MRI).Methods: 35 patients with local atherosclerotic stenosis of middle cerebral artery(MCA-M1)with mild to middle degree of stenosis were recruited in this study retrospectively.According to the atherosclerotic plaque feature about different enhancement by HR MRI findings(including T1WI-FSE?T1WI+C),all patients could be divided into the enhancement group(n=24)and the non-enhancement group(n=11).Wall shear stress(WSS),oscillatory shear index(OSI),velocity and pressure of the stenotic artery wall were calculated by computer and compared between the two groups,after reconstructing 3-dimentional model of hemodynamics based on the cerebral 3-dimension digital subtraction angiography(DSA)image.Then related risk factors of hemodynamics were analyzed in enhanced atherosclerotic plaque of ICAS.Results: There were no significant differences statistically between the two groups in the parameters such as age,sex,degree of artery stenosis,mean arterial pressure(MAP)and some atherosclerosis related medical histories of hypertension,diabetes and hyperlipemia(HLP)et al.(P>0.05).This experiment showed obvious changes of hemodynamics in local artery stenosis.The blood velocity,wall shear stress(WSS)and pressure of artery wall at the stenotic throat was significantly higher than those in proximal normal vessel segment [Velocity:2.65(1.93,4.40)m/s VS 0.29(0.20,0.68)m/s,U=29,P=0.000;WSS:67.87(45.85,78.69)Pa VS 21.03(16.25,30.25)Pa,U=86,P=0.000;Pressure:1630.71(1025.19,3284.93)Pa VS 955.63(563.04,2382.73)Pa,U=401,P=0.013 ].While Oscillatory Shear Index(OSI)at the stenotic throat was lower than that in proximal normal vessel segment[OSI: 0.0027(0.00036,0.0037)VS 0.0069(0.0038,0.020),U=1026,P=0.000];The velocity of the local stenosis [3.64(2.55,4.54)m/s VS 1.93(1.07,2.40)m/s,U=34.5,P=0.000],WSS [70.85(53.60,93.44)Pa VS 41.73(36.28,73.26)Pa,U=55,P=0.005] and pressure of the stenotic artery wall [1875.64(1217.34,3853.02)Pa VS 863.51(552.78,1082.67)Pa,U=49.5,P=0.002] in the enhancement group were much higher than those in the non-enhancement group,but there were no statistically significant differences between the two groups in OSI [0.0068(0.0037,0.019)VS 0.0076(0.0025,0.022)],U=116,P=0.587].Conclusion: Hemodynamic features do exist in local intracranial atherosclerotic stenosis.The velocity,WSS and wall pressure of the local stenosis may be vital risk factors associated with plaque vulnerability of ICAS.