Evaluation Of Coronary Microvascular Dysfunction In Patients With STEMI After PCI By IVIM Technique

Objective:This study is based on cardiac magnetic resonance（CMR）late gadolinium enhancement（LGE）image as the reference standard,aimed to explore the feasibility and value of intravoxel incoherent motion（IVIM）technique in the quantitative evaluation of coronary microvascular dysfunction（CMD）after percutaneous coronary intervention（PCI）in patients with acute ST-elevation myocardial infarction（STEMI）.Materials and Methods:A total of 57 patients diagnosed with acute myocardial infarction（AMI）and performed CMR scan within 1 week after PCI in the First Hospital of Lanzhou University from January 2017 to June 2020 were enrolled.According to the exclusion criteria,27 patients were excluded as ineligible.30STEMI patients and 10 healthy controls were enrolled.All subjects were examined by Siemens Magnetom Skyra 3.0T CMR.Two chamber,three chamber,four chamber,left ventricular short-axis cine images,LGE and IVIM images were obtained for each study subject.The functional parameters and LGE percentage of the left ventricle of each study subject were obtained by image post-processing software.The IVIM related parameters f,D and D^*value of left ventricle were obtained by MITK Diffusion software.SPSS 22.0 software was used for statistical analysis of data in each group.The measurement data with normal distribution were expressed as mean±standard deviation（x±s）,and t-test was used for comparison between two independent samples.The data that did not meet the normal distribution were represented by the median（lower quartile,upper quartile）,and the non-parametric Mann-Whitney U test was used for comparison between the two groups.The intraclass correlation coefficient（ICC）was used to compare the consistency of the IVIM parameter measurements.Receiver operating characteristic curve（ROC）was plotted to analyze the diagnostic efficiency of each parameter.Results:（1）A total of 480 myocardial segments of 30 STEMI patients were included,153 of which were infracted myocardium segments,among which 36segments had microvascular obstruction（MVO）,and 327 segments were remote uninvolved myocardium.A total of 160 normal myocardial segments from 10 healthy controls were included.（2）The ICC test of IVIM parameters of all subjects measured by the same physician twice successively and by different physicians showed good consistency（ICC>0.75）.（3）The f and D^*values of the infarcted myocardium were lower than those of the uninvolved myocardium[0.79（0.77,0.82）vs.0.86（0.84,0.89）,Z=-14.307,P<0.001;27.39（21.86,30.45）×10^-3mm²/s vs.51.66（41.23,63.58）×10^-3mm²/s,Z=-15.866,P<0.001].In further subgroup analysis of the infarcted myocardium,f and D*values of the MVO segments were lower than those of the without MVO segments[0.77（0.69,0.82）vs.0.80（0.78,0.82）,Z=-3.024,P=0.002;15.16（11.68,20.00）×10^-3mm²/s vs.28.91（26.33,30.30）×10^-3mm²/s,Z=-8.496,P<0.001)];In addition,D^*value of uninvolved myocardium of STEMI patients was lower than that of normal myocardium of healthy controls[51.66（41.23,63.58）×10^-3mm²/s vs.53.64（47.20,68.39）×10^-3mm²/s,Z=-1.987,P=0.047].（4）Both f value and D^*value have high diagnostic efficiency for infarcted myocardium and the myocardium with MVO,and D^*value has the highest accuracy.The AUC,cut-off value,sensitivity and specificity of D^*value for the diagnosis of infarcted myocardium were 0.949,36.45×10^-3mm²/s,96.1%and 88.4%.The AUC,cutoff value,sensitivity and specificity of infarcted myocardium with MVO diagnosed by D^*value were 0.968,21.37×10^-3mm²/s,86.1%and 95.7%.（5）The f value and D^*were correlated with the LGE percentage（r=-0.412,-0.821;P=0.024,P<0.001）.With the increase of the degree of late gadolinium enhancement,the f and D^*value tended to decrease,and D^*value had the highest correlation.Conclusion:The results of this study confirm that IVIM technique is feasible to evaluate coronary microvascular dysfunction in STEMI patients after PCI.IVIM parameters can be used to quantitatively evaluate the infarcted myocardium in STEMI patients,and distinguish the occurrence of MVO in the infarcted myocardium.The f value and D*value can have high diagnostic efficiency.IVIM technique provides a new clinical index and a reliable method for noninvasive CMR evaluation of CMD.