Wall Shear Stress Promotes Coronary Artery Disease:A CT Based Analysis

ObjectiveCoronary artery disease is a major health problem threatening human being's health.Low wall shear stress(WSS)is widely assumed to play a key role in the initiation and development of atherosclerosis.Recent study,however,is limited in the pathological and animal study,which has a negative effect for the clinical application of biofluid mechanics.With the improvement of CT spatial and temporal resolution,CT coronary angiography(CTA)has emerged as an attractive,diagnostic modality for detecting coronary artery disease.Based on the high resolution CT images and computational fluid dynamics(CFD),several studies realize the transition from anatomic to functional analysis.The combined CT and CFD analysis develops a new method to investigate the WSS dependent mechanism of atherosclerosis in vivo.The recent study is to investigate the diagnostic ability of CT based CFD to predict the presence of Atherosclerosis and lumen stenosis.Material and MethodsBetween December 2014 to February 2015,28 patients were enrolled in the study.If patients underwent stent-graft and bypass surgery,they were excluded.Other exclusion criteria were as follows: renal insufficiency,allergy to iodinated contrast agents,heart rate could not be controlled under 75 bpm,heart rate variability larger than 20 bpm,local Agatston scoring?100 and patients with undiagnosed image.After exclusion of 7 patients with the criteria mentioned above,21 patients were finally included(6 women,15 men;mean age,65±9.6 years).DICOM format computed tomography angiography(CTA)images were acquired and input into Mimics software.Next,3D realistic models of the coronary artery were reconstructed,surface-meshed and body-meshed.The models were optimized by wiping out irregular details in 3-matic software.Meanwhile,the mimetic and normal 3D models of coronary artery were acquired via removing bulgy atherosclerosis plaques by an experienced professional doctor.In according to the hydromechanics laws,average wall shear–stress(AWSS)and distribution image of hemodynamic parameters were calculatedthrough cycle iterative arithmetic.The measurement were analysed by using ANOVA,with Atherosclerosis and nonatherosclerosis,25% quartile and median as factors.Furthermore,we repeat the ANOVA by dividing the artery segment into region with stenotic atherosclerosis and non-stenotic atherosclerosis.ROC working curve was applied to determine the threshold of WSS,if a significant difference were detected by ANOVA.In addition,the area under the curve was also calculated.Moreover,the sensitivity and specificity of WSS to predict the artery stenosis were determined.We analyzed data in the derivation population to evaluate the relationship between WSS and the presence of plaque by using logistic regression analysis.P value less than 0.05 indicated a statistically significant difference.ResultsAccording to ANOVA analysis,there was no significant difference between atherosclerosis region and non-atherosclerosis region(F<1,p=0.45),while 25% quartile of WSS was lower than that of median(F=37.22,p<0.001).There was no interaction between the two factors(F=17.45,p=0.08).Additional analysis indicated that the WSS of stenotic region was lower than that of region without stenotic region(F=11.124,p<0.005).Similarly,25% quartile of WSS was lower than that of median(F=45.12,p<0.001).However,the interaction was found,which further indicated that the quartile of WSS between region with stenotic plaque and without stenotic region was different,while no difference of median was detected between the two regions.ROC curve showed that 24%quartile of WSS had an overall high diagnostic ability to predict stenotic plaque.The area under the curve was 0.95.With WSS 0.87 Pa as the threshold,a sensitivity of 0.94 and specificity of 0.81 could be obtained in per-segment analysis.According to stepwise logistic regression,WSS was an independent factor for stenotic atherosclerosis.ConclusionWSS is a determinate factor for atherosclerosis.For predicting coronary artery disease,local WSS is a potential risk factor.Moreover,the study indicate that noninvasive CT based CFD could provide helpful reference for clinical risk assessment.