Szolar D H, Saeed M, Wendland M, Sakuma H, Stiskal M A, Derugin N, Higgins C B
Department of Radiology: Karl-Franzens Medical School and University Hospital, Graz, Austria.
Acta Radiol. 1997 Jul;38(4 Pt 1):479-88. doi: 10.1080/02841859709174373.
Considerable clinical interest has focused on the size of ischemic myocardium. Fast MR imaging in conjunction with MR contrast media has the potential to identify hypoperfused and infarcted myocardium. This study used MR perfusion imaging to detect and quantify reperfused ischemic myocardium during a brief coronary occlusion and reperfusion, and to characterize the spatial extent of ischemic and reperfused ischemic myocardium relative to the "true" size of the area at risk as defined in histochemical morphometry at post mortem.
The left circumflex (LCX) coronary artery in 8 dogs was occluded for 15 min followed by reperfusion in order to produce regional reversible myocardial ischemia. Perivascular Doppler probes were used to measure blood flow in the left anterior descending (LAD) and LCX coronary arteries. Fast inversion recovery-prepared gradient-recalled-echo images were acquired to delineate the ischemic area during occlusion, and the area of reversible ischemic injury at 1 and 30 min of reperfusion. The size of ischemic and reperfused ischemic myocardium were compared with the area at risk as determined by histochemical morphometry at post mortem.
During LCX occlusion, LCX flow decreased from 16+/-1 to 0.2+/-0.1 ml/min. On contrast-enhanced images, ischemic myocardium was evident as a zone of relatively low signal intensity (SI) compared to normal myocardium. The size of the ischemic region was significantly smaller (30+/-2%) than at post mortem (36+/-3%; p<0.05). Immediately after reperfusion, LCX flow increased to 83+/-11 ml/min and the contrast medium caused greater enhancement in the reperfused ischemic region than in the normal myocardium (69+/-3 vs 42+/-3 arbitrary units; p<0.05). The increase in regional SI correlated closely with the increase in regional blood flow (r=0.73). At 1 min of reperfusion, the size of the reperfused ischemic myocardium was larger (48+/-3%, p<0.05) than the area at risk measured at post mortem. At 30 min of reperfusion, when the flow returned to baseline values (16+/-2 ml/min), contrast bolus produced no differential enhancement between the 2 myocardial territories.
MR perfusion imaging has the potential to detect and quantify the size of ischemic myocardium and the region of post-occlusive hyperemia in the early reperfusion period. There is a significant direct linear relationship between the regional contrast enhancement of reperfused ischemic myocardium and the blood flow during post-occlusive hyperemia. The difference in the size of the area at risk at MR perfusion imaging and at histochemical morphometry may reflect an influence of coronary collateral circulation.
相当多的临床关注集中在缺血心肌的大小上。快速磁共振成像结合磁共振造影剂有潜力识别灌注不足和梗死的心肌。本研究使用磁共振灌注成像来检测和量化短暂冠状动脉闭塞和再灌注期间再灌注的缺血心肌，并相对于死后组织化学形态测量法所定义的危险区域的“真实”大小来描述缺血和再灌注缺血心肌的空间范围。
对8只犬的左旋支（LCX）冠状动脉进行15分钟的闭塞，随后进行再灌注，以产生局部可逆性心肌缺血。使用血管周围多普勒探头测量左前降支（LAD）和LCX冠状动脉中的血流。采集快速反转恢复准备的梯度回波图像，以描绘闭塞期间的缺血区域以及再灌注1分钟和30分钟时可逆性缺血损伤的区域。将缺血和再灌注缺血心肌的大小与死后组织化学形态测量法确定的危险区域进行比较。
在LCX闭塞期间，LCX血流从16±1降至0.2±0.1 ml/min。在对比增强图像上，与正常心肌相比，缺血心肌表现为相对低信号强度（SI）的区域。缺血区域的大小明显小于死后测量值（30±2% 对比 36±3%；p<0.05）。再灌注后立即，LCX血流增加到83±11 ml/min，造影剂在再灌注缺血区域比正常心肌引起更大的增强（69±3对42±3任意单位；p<0.05）。区域SI的增加与区域血流的增加密切相关（r=0.73）。再灌注1分钟时，再灌注缺血心肌的大小大于死后测量的危险区域（48±3%，p<0.05）。再灌注30分钟时，当血流恢复到基线值（16±2 ml/min）时，对比剂团注在两个心肌区域之间未产生差异增强。
磁共振灌注成像有潜力检测和量化缺血心肌的大小以及再灌注早期闭塞后充血区域。再灌注缺血心肌的区域对比增强与闭塞后充血期间的血流之间存在显著的直接线性关系。磁共振灌注成像和组织化学形态测量法中危险区域大小的差异可能反映了冠状动脉侧支循环的影响。
