MR Imaging For Myocardial Infarction Model Established By Intervention Ebolism Coronary Artery In Mini-Pigs

Purpose:To produce myocardial infarction(MI) of mini-pigs and to study the MR features of MI,including the features on MR perfusion Weighted imaging.To explore the pathological bases of the MR features of MI by comparing the MR features with their histopathology,and then to serve clinical practice and study of using stem sell to treat as a reference.Materials and Methods:Nine male Gui-Zhou mini-pigs were included in the study.Pigs before surgery were served as themselves control. A model of myocardial infarction was induced by transcatheter embolization of the left coronary artery using black silk suture.Before and two days after the surgery,myocardial enzymes,treponin and blood sell were detected.All of the 6 survived pigs were performed MR imaging on 1.5T MR scanner using a synergy phased-array coil before histo-pathology.The MR scanning was performed with both non-enhanced and perfusion weighted MR imaging,from the pre-operation to 1,3,5 weeks after the operation.Pigs, being dead in the operation and one day after surgery,were only performed pre-surgery non-enhanced MR imaging and perfusion weighted MR imaging. Pig dead after 23 days were performed both non-enhanced MR imaging and perfusion weighted MR imaging at pre-surgery,operation to the 1,3 weeks after surgery,respectively.Six weeks after the operaion,all pigs were killed and took out of hearts,and their histo-pathology were then perfon-ned.The MR imaging sequences included T1WI,T2WI,Fiesta and Tags, perfusion weighted MR imaging.Perfusion weighted MR imaging was performed with fast GRE ET pulse sequence with TR=3.31-nsec, TE=1.4msec,FA=23°.It was started at the time of administration of 0.1mg/kg of gadolinium chelate(flow rate 3ml/s).The shape,signal intensity, function changes of the hearts on MR imaging before surgery were, compared with those after surgery.The signal intensity-time(SI-T) plot was generated,and the highest slope rate value,peak-signal,peak-time were calculatedeted,from perfusion weighted MR irnaging.Results:Nine operated pigs were all formed MI.One was dead during the operation,one dead after one day,and another one dead after 23 days.All survived pigs were killed at 6th weeks after surgery.Both macroscopy and microscopy pathohistology result discovered MI forl-ned.Survived rate was 66.7%(6/9).All pigs were performed coronary artery DSA both before and after surgery.The coronary artery of the pigs showed normal on DSA before surgery.After the operation,all DSA showed the coronary artery of the pigs abruption at the level of embolism.All laboratory datas were elevated after the operation.All electrocardiogram were normal before the operation.From 5 to 10 minutes after the operation,3 pig's I,aVL and V1～V5 leads showed abnormal.One pig appeared ventricular fibrillation and was dead at that time.All pigs were normal on non-enhanced MR imaging and perfusion weighted MR imaging before the operation.Six survived pigs were performed non-enhanced MR imaging and perfusion weighted MR imaging at 1,3,5 weeks after operation.On Fiesta images,the motion of the impaired region and the ejection fraction of left ventricle was decreased.However,the thickness of left ventricle wall was normal both in systolic and diastolic phase.The findings of the heart in vitro on non-enhanced MR imaging were comparable to its pathology.Gadolinium-DTPA(Gd-DTPA) was used in the perfusion weighted MR imaging.The hearts of pigs showed normal on perfusion weighted MR imaging before the operation.After surgery, first-pass myocardial perfusion on MR imaging showed low perfusion and delayed myocardial enhancement were found in all 6 pigs.The areas and signal intensity of low perfusion were not significantly changed following the tirne past.Highest slope rate value and peak-signal intensity were reduced after the operation,but peak-time was increased.Highest slope rate value,peak-sgnal intensity,peak time and delayed myocardial enhancement recovered partly after the perfusion time.Conclusion:Intervention ebolism can establish MI model perfectly. Non-enhanced MR imaging and perfusion weighted MR imaging can diagnosis and locate MI,and can detect changes and flow up after MI happened.