| Objective: After myocardial infarction,left ventricular remodeling in patients is often associated with poor prognosis such as sudden cardiac death and heart failure.Segmental wall motion abnormalities are the earliest characteristic manifestations.Cardiac magnetic resonance is considered as the gold standard for assessing the structure and function of the heart,and it can better predict left ventricular remodeling and poor prognosis.In this study,the characteristics of myocardial strain in the delay-enhanced segment of myocardial infarction were compared to understand the difference in strain between the infarcted segment and the adjacent segment and the normal segment,and attempted to predict the myocardial infarct size by comparing the strain characteristics of different segments of myocardial tissue.Methods: 15 normal controls and 15 patients with post-myocardial infarction were enrolled.The short axis,two-chamber,four-chamber,and left ventricular inflow-outflow tract cine images were collected by a real-state precession rapid imaging sequence.After injecting contrast agents,late gadolinium-enhanced(LGE)images of the short axis,two-chamber,four-chamber,and left ventricular inflow-outflow tract were acquired by inversion recovery sequence.The images were processed using a third-party post-processing software CVI42 for post-processing analysis of cardiac function and tissue characteristics.2D circumferential strain(2D-CS)and 2D longitudinal strain(2D-LS)were obtained for each segment.3D circumferential strain(3D-CS),3D longitudinal strain(3D-LS)data were also collected.Myocardial segments were divided into infarction segments,adjacent segments,distant segment and normal segment by LGE results.Compare the statistical differences between the four subgroups.By plotting receiver operating characteristics(ROC)curves,the strain characteristics of different segments of the myocardium were used to predict the extent of myocardial infarction.Results: 1.There was no significant difference in age betweentwo groups(54±11 years vs.61±12 years old,p=0.111).The proportion of males in the control group was lower than that in the myocardial infarction group(60% vs.93.33%,p=0.003).The end-systolic volume of left ventricular end diastolic volume in the MI group was significantly greater than that in the control group(147.47±40.98 ml vs.118.28±28.43 ml,p=0.032;83.72±47.42 ml vs.45.48±15.73 ml,p=0.006).Ejection and cardiac output were both lower than those in the normal control group(46.06±14.36% vs.62.33±6.43%,p<0.001;4.23±1.21 vs.5.39±1.09 l/min,p=0.01).There was no significant difference in stroke volume(72.80±15.19 vs.63.74±15.33,p=0.115).In addition,the diastolic wall thickness in patients with MI was significantly higher than that in the normal control group(8.28±1.45 mm vs.7.73±1.60 mm,p<0.001),while systolic wall thickness,wall thickness,and wall motion are lower than the normal control group(10.91±2.26 mm vs.11.36±2.17 mm,p=0.033;31.87±26.11% vs.51.95±32.98%,p<0.001;5.69±3.79 mm vs.7.71±3.53 mm,p< 0.001).2.To analyze the characteristics of myocardial strain in different segments,LGE positive was used as the gold standard for infarction.The LGE positive segment was listed as the myocardial infarction,and the segment adjacent to the LGE positive segment was listed as Adjacent segments,segments not adjacent to LGE-positive segments were classified as distal segments),and normal segments were normal segments,a total of 4 subgroups.The results showed that the 2D-LS of the infarcted segment was significantly lower than the other three groups(-4.86±17.08% vs.-20.06±11.64%,p<0.001;-4.86±17.08% vs.-18.51±8.55%,p<0.001;-4.86% ± 17.08% vs.-15.90 ± 10.03%,p <0.001),but there was no significant difference in 2D-LS between normal,adjacent,and distant three segments(-20.06 ± 11.64% vs.-18.51 ±8.55%,p=1.000;-20.06±11.64% vs.-15.90±10.03%,p=0.051,-18.51±8.55% vs.-15.90±10.03%,p=0.987).The 2D-CS of the infarcted segment was significantly lower than that of the other three groups(-9.44±15.62% vs.-23.25±8.95%,p<0.001;-9.44±15.62% vs.-22.48±7.52%,p<0.001;-9.44 ±15.62% vs.-18.53±9.65%,p<0.001.The 2D-CS of the infarcted adjacent segment decreased compared with the normal segment(-18.53±9.65% vs.-23.25±8.95%,p=0.003),but There was no significant difference from the distal segment(-22.48±7.52% vs.-18.53±9.65%,p=0.08).The 3D strain results showed that the average 3D-LS of the infarcted segment was significantly lower than that of the normal control segment(-10.55±6.08% vs.-18.07±8.08%,p<0.001),and the distal segment was also decreased.(-10.55±6.08% vs.-14.89±7.25%,p=0.002).Affected by the infarcted segment,the average 3D-LS of the adjacent segment and the distal segment was also decreased compared with the normal segment(-13.10±7.50%vs.-18.07±8.08%,p=0.005;-14.89±7.25% Vs.-18.07±8.08%,p<0.001),but there was no significant difference between the adjacent segment and the distal segment(-13.10±7.50% vs.-14.89±7.25%,p=0.785).Myocardial 3D-CS in the infarcted segment was significantly lower than that in the normal control segment(-12.33±5.45% vs.-21.43±4.90%,p<0.001),and it was also significantly lower than the adjacent segment and the distal segment(-12.33).±5.45% vs.-15.45±5.93%,p=0.002;-12.33±5.45% vs.-17.91±5.60%,p<0.001).In addition,the 3D-CS of adjacent segment and distant segment of MI patients was also significantly lower than that of normal control group(-15.45±5.93% vs.-21.43±4.90%,p<0.001;-17.91±5.60% vs.-21.43±4.90%,p<0.001),while the 3D-CS of the MI segment was also decreased.(-15.45±5.93% vs.-17.91±5.60%,p=0.019).3.According to LGE positive definition of infarction segment,as the gold standard,2D-CS,2D-LS,3D-CS and 3D-LS were used as independent variables,and univariate ROC analysis was performed using Logistic regression model.The results suggest that: It is suggested that there are certain accuracy in predicting the infarcted segment by the four indexes of 2D-CS,2D-LS,3D-CS,and 3D-LS,and the area under the curve is the largest when predicting the infarct segment when using 3D-CS(AUC=0.894,95% confidence interval 95%CI 0.856~0.932,p<0.001.When the 3D-CS cut-point >-15.78%,the specificity of the infarct segment was 87.9% and the sensitivity was 75.0%.In contrast,when the 3D-LS cutpoint was taken to be greater than-18.14%,the sensitivity of the infarct segment was the best,reaching 94.7%.Conclusion: 1.Myocardial infarction in patients with cardiac insufficiency is due to myocardial fibrosis after infarction,further induced left ventricular remodeling,the ability to reduce the overall myocardial deformation,resulting in diastolic and systolic wall motion disorders.2.The 2D-CS and 2D-LS in the infarcted segment were significantly lower than those in the adjacent segment,the distal segment and the normal segment,but there was no significant difference in the 2D-LS between the adjacent,distant and normal segments.The 3D-CS of the infarcted segment of MI patients was lower than that of the normal segment,and the 3D-CS of adjacent and distal segments was also decreased compared with the normal segment.3D-CS of its adjacent segment was also higher than that of the distal segment.3D strain can reflect the strain characteristics of different segments of the heart muscle more than 2D strain,providing more information for quantitative assessment of its strain characteristics.3.The 3D-CS predicts the largest AUC area in the infarcted segment and has the highest prediction accuracy. |
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