| Objective:To investigate the value of cardiovascular magnetic resonance tissue-tracking imaging(CMR-TT)in the quantitative assessment of global and segmental myocardial strain after myocardial infarction,and determine whether strain parameters enable to detect adverse LV remodeling compared to IS.Material and method:Fifty patients with previous myocardial infarction and twenty-seven healthy volunteers as control group were admitted to our research.All participants were performed CMR examination on a 3.0 T MRI scanner.Imaging protocols including FIESTA cine sequence(left ventricle short-axis planes,four chamber and two chanber long-axis planes)and late gadolinium enhancement(LGE).CMR-TT was undertaken using CVI 42 dedicated commercial software.Global peak circumferential,longitudinal,radial strains(GPCS,GPLS,GPRS),segmental peak circumferential,longitudinal,radial strains(PCS,PLS,PRS)in accordance with the sixteen segments model,time to peak,peak systolic strain rate and peak diastolic strain rate were all derived.All positive segments were divided into two groups according to transmural degree based on late gadolinium enhancement(LGE)images(subendocardial infarction ?50%,transmural infarction >50% of wall thickness).All Patients were dichotomized accordance with the existence of LV remodeling.LV remodeling was defined as infarct size(IS)>24%.Means of two continuous variables were compared with independent samples Student's t test or Mann-Whitney U test.Correlation between parameters was assessed by Spearman's rank coefficient.Results:Patients with MI showed significant lower GPRS?GPCS and GPLS than the control group(16.21±9.09% VS 34.59±12.26%?-8.63±3.54% VS-15.83±3.63%?-7.37±2.62% VS-12.85±3.31%).A moderate positive correlation was found between GPRS and LVEF(r=0.56,P<0.001),and negative correlation between GPSC,GPSL and LVEF(r=-0.654,P<0.001,r=-0.682,P<0.001,respectively).A total of 165 transmural infarcted segments and 129 subendocardial infarcted segments were analysed,lower PRS [3.25(-5.57,7.835)% versus 19.94(12.50,30.75)%,P<0.001] and PCS(-3.81±4.60% versus-8.97±4.43%,P<0.001)can be found in transmural infarcted segments compared to subendocardial infarcted segments.PLS between transmural and subendocardial infarcted segments(-4.03±4.88% versus-4.34±4.98%),without however reaching statistical significance(P=0.523).The optimal cut-off value for PRS in the discriminate diagnosis of MI was 8.97% with a sensitivity of 81.8% and specificity of 98.0%.The optimal cut-off value for PCS was-7.56% with a sensitivity of 83.6% and specificity of 72.1%.The remodeling group showed significant decreases among GPCS,GPRS,and GPLS than the non-remodeling group.ROC analysis revealed an optimal cut-off GPRS of 15.45% and GPCS of-6.72% yielded high diagnostic accuracy in the identification of remodelling,which was higher than LVEF.Conclusion:CMR-TT can precisely differentiate the subtype of myocardial infarction,and detect LV remodeling as well,the diagnostic value was superior to conventional functional parameters. |
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