The Study Of Myocardial Fibrosis In Patients With Coronary Chronic Total Occlusion Evaluated By Left Ventricular Layer-Specific Strain

Objective:Coronary chronic total occlusion(CTO)refers to a group of coronary artery lesions with total lumen occlusion caused by atherosclerotic plaque and the occlusion time is maintained for more than 3 months.The transmural extent and volume of myocardial fibrosis(MF)are of great significance for CTO patients to select the clinical treatment strategy and evaluate the prognosis.Layer-specific strain parameters measured by twodimensional speckle tracking echocardiography(2D-STE)have the potential to be one of the parameters for evaluating the extent of MF in patients with coronary artery disease,but there are few studies on detecting the degree of MF in patients with CTO.Therefore,the aim of this study is to explore the application value of layer-specific strain parameters by2D-STE to evaluate the MF in CTO patients,using late gadolinum-enhanced cardiac magnetic resonance imaging(LGE-CMR)as the gold standard,and to provide theoretical basis for guiding clinical treatment and evaluating the prognosis.Methods:Enrollment of patients: Forty patients who were diagnosed with CTO by coronary angiography(CAG)and underwent LGE-CMR from January 2021 to May 2022 in our hospital were enrolled.The clinical data were collected,and Rentrop classification and SYNTAX score were used to analyze the collateral circulation and the complexity of coronary artery lesions according to the results of angiography.CMR: LGE-CMR was performed within 72 hours after CAG.Transmural degree of MF was diagnosed according to the extent of myocardial segment involvement in the 16-segment myocardial model,including no MF,non-transmural MF and transmural MF.Left ventricular fibrosis score(LVFS)and MF volume were calculated.Conventional Echocardiography: Conventional echocardiography was performed within48 hours after CAG.Each myocardial segment was evaluated for the presence of segmental motion abnormalities,segmental myocardial thinning and echogenic enhancement according to the 16-segment myocardial model by two doctors independently.Conventional left ventricular function parameters were measured,including left ventricular end diastolic diameter(LVEDD),left ventricular end diastolic volume(LVEDV),left ventricular ejection fraction(LVEF),left atrial volume index(LAVI),mitral valve early diastolic velocity(MV E),mitral valve late diastolic velocity(MV A)and mitral annular early diastolic mean velocity(e’).2D-STE: Layer-specific strain parameters were measured by 2D-STE,including segmental longitudinal strain(SLS),segmental circumferential strain(SCS)and segmental radial strain(SRS)were measured by 2D-STE: epicardial layer SLS(SLS＿epi),midmyocardial layer SLS(SLS＿mid),endocardial layer SLS(SLS＿endo),epicardial layer SCS(SCS＿epi),midmyocardial layer SCS(SCS＿mid)and endocardial layer SCS(SCS＿endo).The segmental longitudinal and circumferential strain transmural gradients(ΔSLS and ΔSCS)were calculated according to the endocardial and epicardial layer strains.And global longitudinal strain(GLS),global circumferential strain(GCS)and global radial strain(GRS)of all myocardial layers: epicardial layer GLS(GLS＿epi),midmyocardial layer GLS(GLS＿mid),endocardial layer GLS(GLS＿endo),epicardial layer circumferential GCS(GCS＿epi),midmyocardial layer GCS(GCS＿mid)and endocardial layer GCS(GCS＿endo).Patient grouping: Patients were divided into different groups according to LVFS and MF volume,respectively.Taking LVFS equal to 7 points as the cut-off value,the CTO patients were divided into two groups: LVFS<7 group and LVFS≥7 group.In this study,patients were divided into two groups,one with MF volume <9.5% and the other with MF volume ≥9.5%,using 9.5% as the cut-off value.Results:1.General clinical characteristics and CAG findings of the patientsA total of 40 CTO patients were enrolled,with an average age of(62.5±8.1)years,31males(77.50%),and a median disease duration of 21.00 months.CAG findings demonstrated that fifteen patients(37.50%)had CTO lesions in more than two coronary arteries.There were 21 cases(52.50%)with poor collateral circulation(Rentrop grade 0or Rentrop grade 1)and 19 cases(47.50%)with good collateral circulation(Rentrop grade2 or Rentrop grade 3).The mean SYNTAX score was 28.60±12.15.2.MF in CTO patients diagnosed by LGE-CMRA total of 640 myocardial segments were included.LGE-CMR confirmed 364 myocardial segments without MF,210 segments with non-transmural MF,and 66 segments with transmural MF.There were 31 patients with MF in more than one myocardial segment,and 9 patients without MF in any myocardial segment.The mean LVFS was 8.55±6.64.The mean MF volume was(8.38±8.18)%.3.The evaluation of LVFS by layer-specific global strain(1)Grouping of patients:There were 15 patients in LVFS<7 group and 25 patients in LVFS≥7 group.(2)Comparison of general clinical characteristics and CAG findingsThere were no significant differences in age,disease duration,body surface area(BSA),smoking history and other general clinical characteristics between the two groups(P>0.05).There was no significant difference in the number of CTO vessels involved,collateral circulation and SYNTAX score between the two groups(P>0.05).(3)Comparison of left ventricular function parameters in patientsThere was no significant difference in conventional left ventricular function parameters between the two groups(P>0.05).In the comparison of layer-specific strain parameters,GLS＿endo showed significant difference(P=0.046).(4)Correlation analysis between layer-specific global strain and LVFSGLS＿epi,GLS＿mid and GLS＿endo were negatively correlated with LVFS(P<0.05).(5)The evaluation of LVFS by layer-specific global strain parameters1)Univariate Logistic regression analysis showed that GLS＿mid,GLS＿endo,GCS＿mid and BSA were associated with the degree of LVFS in CTO patients(P<0.10).2)Multivariate Logistic regression analysis showed that GLS＿mid and GLS＿endo could detect LVFS independently after adjusting for other clinical characteristics and CAG findings of patients.3)The ROC curve showed that AUC of GLS＿mid and GLS＿endo in evaluating the degree of LVFS was 0.681 to 0.696.Combined with BSA,hypertension and hyperlipidemia,the AUC of clinical models in evaluating LVFS did not significantly improve(P>0.05).4.The evaluation of MF volume by layer-specific global strain(1)Grouping of patients:There were 24 patients in the MF<9.5% group and 16 patients in the MF≥9.5% group.(2)Comparison of general clinical characteristics and CAG findingsThere was no significant difference in general clinical characteristics between the two groups(P>0.05)except for the proportion of patients taking antiplatelet drugs(P=0.002).SYNTAX score was significantly higher in patients with a MF volume ≥9.5% than in those with a MF volume <9.5%(P=0.038).(3)Comparison of left ventricular function parameters in patientsThe comparison of conventional left ventricular function parameters showed that the ejection fraction(LVEF)was decreased in the MF volume ≥9.5% group(P<0.05).GLS＿epi,GLS＿mid,GLS＿endo,GCS＿epi and GCS＿mid decreased in the MF volume≥9.5% group(P<0.05).(4)Correlation analysis between layer-specific global strain and MF volumeGLS＿epi,GLS＿mid and GLS＿endo were negatively correlated with MF volume.(5)The evaluation MF volume by layer-specific global strain parameters1)Univariate Logistic regression analysis showed that the duration of CTO,antiplatelet therapy,SYNTAX score,LVEDD,LVEF,GLS＿epi,GLS＿mid,GLS＿endo,GCS＿epi and GCS＿mid were associated with MF volume in CTO patients(P< 0.10).2)Multivariate Logistic regression analysis showed that GLS＿epi,GLS＿mid and GLS＿endo,antiplatelet drug and LVEF could detect MF volume independently after adjusting for other clinical characteristics and CAG findings of patients.3)The ROC curve showed that the AUC of GLS＿epi,GLS＿mid,GLS＿endo,GCS＿epi and GCS＿mid for evaluating MF volume was 0.702 to 0.783.Combined with the course of disease and the use of antiplatelet drugs,The AUC of GLS＿epi,GLS＿mid,GLS＿endo was0.906-0.909.5.The evaluation of myocardial segments with transmural degree of MF by layerspecific segmental strain(1)Conventional echocardiographic findings of myocardial segments with different transmural degrees of MFAmong the included myocardial segments,there were 122 myocardial segments with abnormal conventional echocardiography(abnormal myocardial segmental motion,thinning or echogenic enhancement),and 518 myocardial segments with normal conventional echocardiography(abnormal myocardial segmental motion,thinning and echogenic enhancement).Among the myocardial segments with normal conventional ultrasound,343(94.23%)were without MF,151(71.90%)were with non-transmural MF,and 24(36.36%)were with transmural MF.There were 21(5.77%)segments without MF,59(28.10%)segments with non-transmural MF,and 42(63.64%)segments with transmural MF.(2)Layer-specific segmental strain of myocardial segments with different MF transmural degreesSLS was obtained in 626 segments and SCS and SRS were obtained in 576 segments,including 336 segments without MF.Compared with the myocardial segments with normal conventional echocardiography,the myocardial segments with abnormal conventional ultrasound showed a downward trend in layer-specific strain parameters.(3)The ability of layer-specific segmental strain to evaluate the transmural extent of MF in myocardial segments with normal conventional echocardiography1)SLS＿epi,SLS＿mid,SLS＿endo,ΔSLS and SCS＿epi were significantly lower in nontransmural MF segments than in non-transmural MF segments(P<0.05),while SLS＿epi and SLS＿mid were significantly lower in transmural MF segments(P<0.05).However,there was no significant difference in layer-specific segmental strain between nontransmural MF segments and transmural MF segments(P>0.05).2)The ROC curve showed that SLS＿epi,SLS＿mid,SLS＿endo and SCS＿epi could detect non-transmural MF segments,with an AUC of 0.567 to 0.583,a sensitivity of 31.30% to72.30%,and a specificity of 45.30% to 82.90%.After the combination of each layerspecific strain parameter,the AUC was 0.616,the sensitivity was 75.20%,and the specificity was 43.50%.3)The ROC curve showed that SLS＿epi and SLS＿mid could detect the myocardial segments of transmural MF,the sensitivity was 72.70%-81.80%,and the specificity was41.60%-56.00%.After the combination of each layer-specific strain parameter,the AUC was 0.678,the sensitivity was 68.40%,and the specificity was 66.60%Conclusions:1.GLS＿mid and GLS＿endo were negatively correlated with the degree of LVFS in CTO patients,which can be used to evaluate the degree of LVFS.2.GLS＿epi,GLS＿mid and GLS＿endo were negatively correlated with MF volume in CTO patients.Combined with the use of antiplatelet drugs and the course of disease,layerspecific strain can effectively evaluate MF volume.3.SLS＿epi,SLS＿mid,SLS＿endo and SCS＿epi can be used to evaluate myocardial nontransmural MF.4.SLS＿epi,SLS＿mid can be used to evaluate myocardial transmural MF.