Study Of Association Between Left Ventricular Systolic Mechanical Indexes And Computed Tomography Myocardial Perfusion In Patients With Chronic Coronary Syndrome

BackgroundCoronary heart disease(CHD)has become one of the most serious cardiovascular diseases nowdays.With the deepening understanding of CHD,the concept of chronic coronary syndrome(CCS)was put forward in 2019.Besides the structural changes of coronary arteries,attention should be paid to the myocardial ischemia caused by coronary artery functional changes such as coronary artery spasm and microvascular disease.Coronary computed tomography angiography(cCTA)and dynamic stress computed tomography myocardial perfusion Imaging(CT-MPI)"one-stop" examination provides a quantitative analysis of coronary artery anatomy and left ventricular myocardial blood flow.However,it can’t directly evaluate the systolic function of the left ventricle accurately.Myocardial ischemia can lead to a corresponding decrease in myocardial energy,resulting in cardiac systolic and diastolic dysfunction.Transthoracic echocardiography plays an important role in evaluating left ventricular function.Global longitudinal strain(GLS),global work index(GWI),global contractive work(GCW),global waste work(GWW)and global work efficiency(GWE)can be obtained via two-dimensional speckle tracking,and it has been reported that they can provide more information on the changes in cardiac function in patients with CHD than left ventricular ejection fraction(LVEF).However,the association between these mechanical indicators and myocardial perfusion in patients with CCS is not yet clear.In addition,the association between left ventricular local systolic mechanical indexes,such as longitudinal strain(LS)and work index(WI),and local myocardial perfusion remains to be explored.Objectives1.To investigate the association between cardiac mechanical indexes measured by transthoracic echocardiography and myocardial perfusion in patients with CCS.2.Evaluate the clinical value of left ventricular systolic mechanical indexes in judging reduced myocardial perfusion.Methods1 Study populationThere were 88 patients with CCS,including 44 males and 44 females,with an average age of 57.23±10.37 years old.All patients underwent transthoracic echocardiography,cCTA and dynamic stress CT-MPI "one-stop" examination.2 Research methods2.1 Transthoracic echocardiographyTransthoracic echocardiography was performed by GE Vivid E95 ultrasound diagnostic instrument(GE)with a 3.5 MHz phased array transducer(M5S).Patients in left lateral decubitus position were connected with synchronous electrocardiograph,and clear two-dimensional images of three consecutive cardiac cycles were collected from four sections including parasternal long axis view,apical four-chamber view,apical two-chamber view and apical three-chamber view.These images were stored in DICOM format for off-line analysis.Blood pressure was measured before and after examination,and mean values of systolic and diastolic blood pressure were calculated2.2 Images processing and indexes acquisitionThe analysis was performed by the EchoPAC Ultrasound Workstation(GE).On the parasternal long axis view,standard two-dimensional mode was used to measure left ventricular basic structural indicators,including left ventricular internal diameter at end-diastole(LVIDd),interventricular septal thickness(IVST)and left ventricular posterior wall thickness(LVPWT).The modified Simpson method was used to calculate LVEF on the apical four-chamber view and apical two-chamber view.Q analysis was selected for analysis.At the end of systolic period,the mitral ring and the left ventricular apex were selected along the endocardium of the left ventricle on apical four-chamber view,apical two-chamber view and apical three-chamber view.The software automatically recognized the area between the endocardium and epicardium.Subsequently,the time of aortic valve closure was automatically identified on the apical three-chamber view.The left ventricular GLS and LS bull-eye maps of 17 segments of the left ventricle were calculated.According to the distribution of coronary arteries,17 segments were classified into three regions corresponding to three main coronary arteries,and the average LS of each segments in each region was defined as the myocardial LS of the region.Enter the mode of myocardial work analysis,the closing and opening times of the mitral and aortic valves were determined on the apical three-chamber view,and then the mean values of systolic pressure were input to replace the peak left ventricular pressure.The left ventricular GWI,GCW,GWW and GWE were obtained.Similarly,the WI bull-eye maps were calculated and the average WI of each segments in each region was defined as the myocardial WI of the region.2.2.1 Basic structural indexes of left ventricle(1)LVIDd;(2)IVST;(3)LVPWT.2.2.2 Global systolic function indexes of left ventricle(1)LVEF;(2)GLS;(3)GWI;(4)GCW;(5)GWW;(6)GWE.2.2.3 Local systolic function indexes of left ventricle(1)LS;(2)WI.3 cCTA and dynamic stress CT-MPI "one-stop" examination3.1 Images acquisition and processingThird-generation dual-source CT was used to perform cCTA and dynamic stress CT-MPI "one-stop" examination.The images of cCTA and dynamic stress CT-MPI"one-stop" examination were quantitatively analyzed by using the medical image processing software(Syngo.via,Siemens Healthcare).3.2 Quantitative evaluation of cCTAPatients with severe calcification were excluded.Using the proximal and distal segment to the stenosis site as reference,the percentage of the lumen stenosis caused by plaque was defined as 100%-(lumen diameter at the stenosis/the average of the proximal and distal lumen diameter).According to the degree of stenosis,coronary arteries were divided into non-significant stenosis group and significant stenosis group.Non-significant stenosis should meet the following conditions simultaneously:(1)the stenosis of left anterior descending coronary artery,left circumflex coronary artery and right coronary artery was<70%,(2)the stenosis of left main coronary artery was<50%.If the above conditions could not be met at the same time,the coronary artery was classified as significant stenosis(if the stenosis of left main coronary artery≥50%,the downstream left anterior descending coronary artery and left circumflex coronary artery were classified as significantly stenosis).At patient level,patients with significant stenosis were classified as significant stenosis group.Otherwise,they were classified as non-significant stenosis group.3.3 Quantitative evaluation of dynamic stress CT-MPI3.3.1 Quantitative evaluation of global myocardial perfusionThe medical image processing software(Syngo.via,Siemens Healthcare)was used to automatically calculate the myocardial blood flow in each segment of the heart.The ratio of the myocardial blood flow of each segment to the maximum myocardial blood flow of the 17 segments was calculated.The ratio of myocardial blood flow of each segment was assigned to the integral value:normal(>0.75)was assigned to 0;mild abnormality(0.675<ratio≤0.75)was assigned to 1;moderately abnormality(0.6<ratio≤0.675)was assigned to 2;severe abnormality(ratio≤0.6)was assigned to 3;no perfusion(ratio=0)was assigned to 4.The scores of the 17 segments were added to calculate the summed stress score(SSS).At patient level,SSS≥4 was considered to be reduced myocardial perfusion.The patients were divided into normal myocardial perfusion group and reduced myocardial perfusion group.3.3.2 Quantitative assessment of local myocardial perfusionAccording to the distribution of coronary arteries,17 segments were classified into three regions corresponding to three main coronary arteries.If at least two adjacent sections of each region with reduced myocardial perfusion in the same position were found in the left ventricular short axis sections(basal part,middle part,apical part and apical cap),the regional myocardial perfusion reduced.The myocardium was divided into normal myocardial perfusion region and reduced myocardial perfusion region.Results1 Comparison between reduced myocardial perfusion group and normal group1.1 Clinical dataOf 88 patients with CCS,35 individuals were in the reduced myocardial perfusion group and 53 individuals were in the normal myocardial perfusion group.Significant differences were not found in sex,age,body mass index(BMI),systolic blood pressure,diastolic blood pressure,heart rates,smoking history,history of hypertension,history of diabetes mellitus,family history of CHD and serum low density lipoprotein-cholesterin(LDL-C).1.2 Basic structural indexes of left ventricleSignificant differences were not found in IVST,LVPWT and LVIDd between two groups.1.3 Global systolic function indexes of left ventricleNo significant differences were found in LVEF.Compared with normal myocardial perfusion group,absolute value of GLS,GWI,GCW and GWE were significantly decreased in reduced myocardial perfusion group(p<0.05).GWW was significantly increased(p<0.05).1.4 Local systolic function indexes of left ventricleA total of 264 regions corresponding to coronary arteries in 88 patients were included for regional analysis,including 43 regions with decreased perfusion and 221 regions with normal perfusion.Absolute value of LS and WI were significantly lower in the reduced myocardial perfusion regions(p<0.05).2 Comparison between reduced myocardial perfusion group and normal group in the non-significant coronary artery stenosis group2.1 Clinical dataThe following patients were excluded:(1)10 patients had underwent percutaneous coronary intervention(PCI);(2)5 patients with left main coronary artery stenosis>50%or at least one coronary artery branch stenosis≥70%;(3)6 patients with calcification score>400 in at least one coronary artery branch.Of 67 patients in the non-significant stenosis group,22 patients were in reduced myocardial perfusion group,and 45 patients were in normal myocardial perfusion group.Significant differences were not found in clinical data.2.2 Basic structural indexes of left ventricleNo significant differences were found in IVST,LVPWT and LVID.2.3 Global systolic function indexes of left ventricleNo significant differences were found in LVEF and GCW.Absolute value of GLS,GWI and GWE were significantly lower in reduced myocardial perfusion group(p<0.05).GWW was significantly increased(p<0.05).2.4 Local systolic function indexes of left ventricleThe following coronary artery dominated myocardial regions were excluded sequentially:(1)15 regions with stented coronary artery;(2)6 regions with coronary artery branches stenosis ≥70%or its upstream left main coronary artery with stenosis≥50%;(3)9 regions with coronary artery calcification score≥400.A total of 234 myocardial regions were included in the regional analysis,including 29 regions with reduced perfusion and 204 regions with normal perfusion Absolute value of LS was lower in regions with reduced myocardial perfusion.However,no significant differences were found in WI.3 Logistic regression analysis and ROC analysis of left ventricular global systolic function indexes and myocardial perfusion3.1 Logistic regression analysis and ROC analysis of all CCS patientsUnivariate logistic regression analysis showed that GLS,GWI,GCW,GWW and GWE were associated with myocardial perfusion(p<0.05).Binary multivariate stepwise logistic regression analysis showed that GCW and GWW were independently correlated with myocardial perfusion(p<0.05).ROC analysis showed that the AUC of GWE was the largest,which was 0.885(p<0.05),the sensitivity was 71.43%and the specificity was 92.45%when GWE≤95%was the cut-off value3.2 Logistic regression analysis and ROC analysis of CCS patients in the group with non-significant coronary artery stenosisUnivariate logistic regression analysis showed that GLS,GWI,GWW,GWE were associated with myocardial perfusion(p<0.05).Binary multivariate stepwise logistic regression analysis showed that GWI and GWW were independently correlated with myocardial perfusion(p<0.05).ROC analysis showed that the AUC of GWE was the largest,which was 0.856(p<0.05),the sensitivity and specificity were 77.27%and 77.28%when GWE≤96%was taken as the cut-off value.4 Logistic regression analysis and ROC analysis of left ventricular local systolic function indexes and myocardial perfusion4.1 Logistic regression analysis and ROC analysis of all regionsUnivariate logistic regression analysis showed that LS and WI were associated with myocardial perfusion(p<0.05).ROC analysis showed that the AUC of LS was the largest,which was 0.652(p<0.05).When-22%was taken as the cut-off value,the sensitivity and specificity are 65.12%and 58.82%respectively.4.2 Logistic regression analysis and ROC analysis of all regions with non-significant coronary artery stenosisUnivariate logistic regression analysis showed that only LS was associated with myocardial perfusion(p<0.05).ROC analysis showed that the AUC of LS was 0.616(p>0.05).Conclusions1.Lower absolute value of GLS,GWI,GCW,GWE and higher GWW in CCS patients were associated with reduced myocardial perfusion.GLS and myocardial work parameters had certain diagnostic ability for reduced myocardial perfusion,and GWE has the most significant diagnostic value,which is better than GLS.2.Lower absolute value of GLS,GWI,GWE and higher GWW were associated with reduced myocardial perfusion in CCS patients with non-significant coronary artery stenosis.GWE also had the most significant value in diagnosis of reduced myocardial perfusion,and is superior to GLS.3.In CCS patients,regional absolute value of LS and WI were significantly decreased in the region with reduced myocardial perfusion.However,they had no significant diagnostic value in regions of reduced myocardial perfusion with non-significant coronary artery stenosis.