ABSTRACT
Objective To study the MRI features and its ultrastructural pathology basis in different myocardial injury areas after acute infarction.Methods 10 rabbits were given ligation of left anterior descending branch 24 hours to make pathologic models.All animals underwent conventional MRI,contrast media dynamic enhancement MRI,cine-MRI and dobutamine stress test.Myocardial blood flow was measured with radioactive micropheres to define risk regions.Ischemic and infarcted regions were defined as Even's blue and 2,3,5triphenyltetrazolium chloride(TTC)negative regions respectively,and made electron microscopy specimens to observe the changes of mitochondria and myofibril.The myocardial ultrastructural injury was scored and graded.Results There were no significant change on T 1WI,but the signal intensity on T 2WI increased significantly after AMI.The diseased myocardium became thinning were seen in 40% cases,and the abnormal flowing high signal were seen in 60% cases.The dynamic enhancement time-signal intensity curves were different in normal,ischemic and infarcted regions.Cine-MRI showed the cardiac wall movement impairing and the wall thick thinning,but the wall movement reinforcing and the wall thick thickening after dobutamine stress.The water content of ischemic and infracted myocardium were marked higher than normal myocardium.The myocardial blood flow in diseased regions were decreased significantly than that in normal regions.The volume density and numerical density of mitochondria in different injury regions showed significant differences.Conclusion MRI appearances of AMI were associated with the injury degree of myocardial ultrastructure and the residual myocardial blood flow.
