18F-FDG PET/CT心肌“缺血记忆”显像的实验研究

摘要

Objective To explore whether the existence and duration of ischemia measured by dynamic 18F-FDG PET/CT imaging correlated with the extent of myocardial ischemia in a canine model of myocardial ischemia-reperfusion.Methods Canine coronary artery occlusion was carried out for 20 min (n =4) and for 40 min (n =4) followed by 24 h of open-artery reperfusion.All dogs underwent dynamic 18F-FDG PET/CT and 99Tcm-MIBI SPECT imaging at baseline and 1 h and 24 h after reperfusion.Quantitative analysis of myocardial 18F-FDG uptake was performed using Carimas Core software,and the extraction ratio of 18F-FDG (K) was calculated by the ratio of 18F-FDG uptake rate in the ischemic area (kischemia) and normoperfused region (knormoperfused).Echocardiographic data were also acquired between each PET/CT imaging study to detect the wall motion in the ischemic and normoperfused myocardium.Paired t test and non-parametric statistical tests,measured by SPSS 19.0,were used to analyze the data.Results Coronary occlusion produced sustained,abnormal wall motion in the ischemic region for more than 1 h.Similar K values were demonstrated between the 20 min and 40 min groups at baseline (1.02 ±0.06 and 1.03 ±0.05,Z =-0.29,P ＞0.05).At 1 h after reperfusion,the reperfusion regions showed normal perfusion but with increased 18F-FDG uptake,which was higher in the 40 min ischemic group than in the 20 min ischemic group (2.31 ±0.13 and 1.87 ±0.09,Z=-2.31,P＜0.05).At 24 h after reperfusion,however,only the 40 min ischemic group showed slightly higher 18F-FDG uptake than baseline (1.15 ± 0.02 and 1.03 ±0.05,t =4.32,P ＜ 0.05),whereas no significant difference was found in the 20 min ischemic group (1.05 ± 0.04and 1.02 ± 0.06,t =0.87,P ＞ 0.05).Histological examination of the ischemic myocardium from both groups revealed neatly arranged cells without interstitial edema,hemorrhage nor inflammatory response.Conclusions Myocardial " ischemic memory" was correlated with the extent of myocardial ischemia.18F-FDG imaging of " ischemic memory" may have important value in the diagnosis and treatment of patients with acute coronary syndrome.%目的 通过犬18F-FDG PET/CT动态显像探讨缺血心肌葡萄糖代谢改变(也称“缺血记忆”)和缺血程度的关系.方法 将8条杂种犬用随机抽签法分为球囊封堵20 min组(4条)和40 min组(4条),所有犬均行基础、缺血-再灌注1h和24 h的18F-FDG PET/CT动态心肌代谢显像(禁食12h以上),以及99Tcm-MIBI SPECT心肌灌注显像.利用葡萄糖摄取定量分析软件(Carimas Core)计算冠状动脉封堵区和非缺血区心肌的葡萄糖摄取率k(k缺血和k非缺血),获得两者比值K(K=k缺血/k非缺血).在3次PET/CT显像同期分别进行心脏超声检查,评价室壁运动情况.所有显像完成后处死犬,分别取缺血区、非缺血区心肌组织行组织病理学检查.同一实验组前后比较采用配对t检验,其他采用非参数检验分析.结果 2组犬基础心肌灌注显像未见异常,预封堵区心肌/非缺血区心肌18F-FDG摄取率比值K差异无统计学意义(1.02 ±0.06与1.03±0.05,Z=-0.29,P＞0.05),室壁运动正常.缺血-再灌注1h后2组心肌灌注显像亦未见异常,但缺血区18F-FDG摄取增加,40 min组的K值高于20 min组(2.31±0.13与1.87 ±0.09,Z=-2.31,P＜0.05),缺血心肌出现不同程度的室壁运动减弱.缺血-再灌注24h后2组心肌灌注显像未见异常,但40 min组的K值仍稍高于基础状态(1.15±0.02与1.03 ±0.05,=4.32,P＜0.05),而20 min组的K值与基础状态比较差异无统计学意义(1.05±0.04与1.02±0.06,=0.87,P＞0.05),2组室壁运动均未见异常.心肌组织检查示2组缺血部位心肌细胞排列整齐,心肌细胞间质无水肿出血,未见心肌细胞肌浆凝集或肌溶性破坏,也未见炎性反应.结论 心肌“缺血记忆”与缺血程度相关.18F-FDG PET/CT心肌“缺血记忆”显像可能在急性冠状动脉综合征患者的诊断、治疗方面具有重要应用价值.