Detection Of Myocardial Infarction Segment By DE - MRI And Its Correlation With Coronary Artery Stenosis And Ventricular Remodeling

Objectives:The advantages of delayed-enhancement MR imaging(DE-MRI) in detecting the myocardial infracted scar have been confirmed by many experiments, but DE-MRI has been applied clinically rarely. In addition, we know few about the relationship between transmural necrosis from subendocardial necrosis with the degree of coronary artery stenosis. In this study, we will do a preliminary research focus on the problem, in order to investigate the relationship between the transmural extents of myocardial infarction with the degree of coronary artery stenosis.Materials and Methods:DE-MRI were performed in40patients who have been diagnosed coronary atherosclerotic heart disease clinically and myocardial infarction scars were found. All patients were examined by DSA in the same week performing MRI examination. The analysis of DE-MRI imagines including the number of infracted myocardium segments and transmural necrosis from subendocardial necrosis, the score of myocardial infarctions by DE-MRI were assessed. According to the transmural extent of myocardial infarction, the score were divided into5levels:0=no infarction,1=transmural extent of infarction1-25%of left-ventricular wall thickness,2=26-50%,3=51-75%, and4=76-100%. The degrees of coronary artery stenosis were assessed by Gensini score:1=1-25%of coronary artery stenosis,2=26-50%,4=51-75%,8=76-90%,16=91%-99%,32=100%. The correlation between the transmural extents of myocardial infarction with the degree of coronary artery stenosis was analyzed. All statistics datas were processed by SPSS13, the result was significant if P＜0.05.Results:(1)126myocardial infracted segments were detected in40patients:there were60 stenotic arteries found in37patients.(2) The score of the myocardial infracted scar detected by DE-MRI was307, the Gensini score of coronary artery stenosis was587, there was correlation between them, the correlation coefficient rs=0.786(P<0.05)(3) There was rank correlation between the transmural extents of myocardial infarction with the degree of coronary artery stenosis, the correlation coefficient rs=0.786(P<0.05).81.74%segments of myocardial infarction were found in subjects with severe stenosis of coronary artery(>50%).(4) According to the delayed reinforcement sections by DE-MR, the blood vessels supplying the corresponding regions could be speculated based on the standard of very severe stenosis of coronary artery(≥70%), the Sensitivity and specificity were76.47%and68.77%respectively.(5) The myocardial infarctions were found by DE-MRI in patients with no significant coronary stenosis, there were18.26%segments of myocardial infarction found in subjects with mild stenosis of coronary artery(≤25%). In the region of coronary stenosis less than50%, the transmural extent of myocardial infarction appeared mostly subendocardial myocardial infarction(60.87%).Conclusion:The correlation between the total score of myocardial infarctions by DE-MRI with the total score of coronary artery stenosis was high, more serious the stenosis were, higher the myocardial infarcted transmural extent. The sensitivity and specificity is relatively high through DE-MRI imaging for speculating coronary artery stenosis. Besides, not only the myocardial infarctions of patients whose coronary arteries were normal could be detected by DE-MRI, but also small myocardial infarctions that might be missed by SPECT could be found, so that the recovery of the heart function after infarction could be forecasted. In a word, DE-MRI was an efficient method in detecting myocardial infracted scars:it is helpful to evaluate coronary artery and myocardial infarction combined with DSA. Objectives:The morphologic changes such as wall thickness could be reflected clearly by MRI as a result of its advantages in the resolution for soft tissue, so MRI has become a routine method in evaluating the myocardial function. Currently more attention has been focused on the detection of myocardial infarction by DE-MRI, we know few about the relationship between myocardial infarction with the regional movement and the wall thickness after ventricular remodeling. In this study, we will do a preliminary research focus on this question, DE-MRI was performed in patients who have been diagnosed chronic myocardial infarction, the relationship between the degree of myocardial infarction with wall motion(WM), ejection fraction(EF), wall thickening (WT), wall thickening ration(WTR), in order to investigate the relationship between chronic myocardial infarction with ventricular remodeling.Materials and Methods:DE-MRI were performed in20patients who have been diagnosed chronic myocardial infarction clinically and myocardial infarction scars were found. All patients were examined by MRI cine scanning, the short axis images of left ventricular were transferred to the workstation, ejection fraction(EF), wall thickening (WT), wall thickening ration(WTR) were calculated by Argus. The score of wall motion(WM) were assessed by the following standard:1=normal;2=hypomotility;3=akinesis; and4=countermove;5=ventricular aneurysm. The correlation between the score of myocardial infarction by DE-MRI with WT, WTR, the score of WM and EF were assessed.Results:(1)All patients were divided into two groups by the standard that EF=50%, the difference of WT, WTR was significant between the two groups. The WT,WTR of the group that the heart function was better were higher than the group that with worse heart function.(2)There was correlation between EF and the score of WM, the correlation coefficient rs=-0.730(P<0.05)(3)The score of DE-MRI inversely related to WT, WTR, EF (rsl=-0.788、rs2=-0.756、 rs3=-0.804) positively related to WM (rs4=0.811)Conclusion:Cardiac MRI cine-imaging can give the quantitative analysis of left ventricular (LV), including wall thickening rate, wall motion and ejection fraction. The transmural extent of myocardial infarcted segments by DE-MRI has correlation with LV wall thickening rate, wall motion and ejection fraction. The more serious transmural myocardial infarction are found, the worse LV wall motion and wall thickening rate would be. Thus, the cardiac MRI cine-imaging combined with DE-MRI can reflect the changes of left ventricular remodeling, and predict the severity of left ventricular remodeling. It also has prognostic value in patient with chronic myocardial infarction.