兔心肌梗死过程MRI上心室壁变薄的病理基础研究

A Study on MR Imaging of the Thinning of Left Ventricular Wall during Myocardial Infarction in Rabbits in Correlation with Its Pathology

目的探讨兔心肌梗死不同时期在MRI上心室壁变薄的病理基础。方法通过结扎冠状动脉制备兔心左室前壁梗死模型,行多次心脏MRI检查,对正常及各缺血时间点梗死心肌标本进行TTC染色、HE染色及透射电镜观察。结果(1)MRI缺血早期缺血室壁即轻度变薄,以收缩期明显;然后逐渐加重,收缩期及舒张期均变薄;至4周瘢痕形成后,其厚度固定不变。(2)TTC染色缺血30min缺血室壁轻度变薄;1h～2周,梗死室壁明显变薄;4周后,梗死区菲薄,纤维瘢痕形成。(3)光镜缺血30min缺血区肌纤维间隙变窄,血管闭塞,肌纤维变细;1h细胞间隙稍有增宽,肌纤维断裂,逐渐加重,肌纤维呈波浪状改变;4周梗死区纤维疤痕形成。(4)电镜缺血30min肌原纤维I带增宽,血管闭塞;1h肌纤维远端肌原纤维断裂;4h肌原纤维有溶解。结论缺血后心室壁变薄的原因各期不同,缺血早期是由于心室内张力牵拉使心肌细胞呈舒张状态变细、间隙变窄及血管闭塞所致;急性梗死期,主要因心室内张力牵拉及心肌纤维断裂所致;而梗死后期则由纤维瘢痕收缩引起。

Objective To study the pathologic basis of thinning of anterior wall of left ventricle at different stage in myocardial infarction with MR in rabbits.Methods Cardiac cine-MR imaging was performed.The cardiac specimens were stained with TTC,HE and studied under electron microscope.Results (1) MRI:The ischemic walls became thin slightly in 30 minutes, it being evident in systole.The walls became markedly thin in both systole and diastole after 1 hour.Myocardial fibrosis appeared at 4th week,and then the thinning of walls became fixed.(2) TTC-Staining:The walls of the ischemic region became thin slightly in 30 minutes.The walls of infracted regions became thin distinctly in 1 hour,and became thinner gradually.The infarcted regions formed fibrosis in 4 weeks,the thinning of the walls being fixed.(3) Light Microscope:The myofibers and the interstitium became thin, the vessels occluded in 30 minutes.A few fibers ruptured in 1 hour.The fibrotic scars were formed in 4 weeks.(4) Electron Microscope:The band I of myofrils widened and the vessels occluded in 30 minutes, the peripheral myofibrils ruptured in 1 hour, and the fibrils dissolved in 4 hours.Conclusion The causes of thinning of the anterior walls of the left ventricles are different according to different infarct stage.At the early stage of ischemia,it results from occlusion of vessels and relaxation of myofibers caused by the pulling of ventricular clamps,so the fibers became thin with narrowed interstitium.In acute infarct stage,the thinning is caused by rupture of the fibrils and fibers.At the chronic stage, it is because of the formation of fibrotic scars.