Saeed M, Wendland M F, Yu K K, Lauerma K, Li H T, Derugin N, Cavagna F M, Higgins C B
Department of Radiology, University of California San Francisco 94143.
Circulation. 1994 Sep;90(3):1492-501. doi: 10.1161/01.cir.90.3.1492.
The current treatment of many cases of acute myocardial infarction involves the use of thrombolytic agents. Evaluation of this therapy requires determination of the success of reperfusion and assessment of the presence and extent of infarction in the reperfused territory. The present study was designed to simulate in rat models several possible outcomes of reperfusion therapy: (1) successful reperfusion and absence of myocardial infarction, (2) successful reperfusion and presence of myocardial infarction, and (3) unsuccessful reperfusion. The usefulness of contrast-enhanced fast magnetic resonance (MR) imaging in defining the success of reperfusion was investigated. The dynamic effects were examined of low and high doses of gadolinium-BOPTA/dimeglumine (Gd-BOPTA/dimeg) on myocardial signal using MR inversion recovery echo planar imaging (IR-EPI) and gradient recalled echo planar imaging (GR-EPI), respectively.
Rats were subjected to one of the following regimens: reperfused reversible myocardial injury (n = 9), reperfused irreversible myocardial injury (n = 9), and occlusive infarction (n = 9). MR echo planar images were acquired every 1 or 2 seconds before, during, and after administration of Gd-BOPTA/dimeg. In all groups, normal myocardial signal was sharply increased on IR-EPI and decreased on GR-EPI at the peak of the bolus, followed by a gradual decline to baseline. In animals subjected to reperfused reversible myocardial injury, normal and previously ischemic regions were indistinguishable during and after the passage of Gd-BOPTA/dimeg. On the other hand, enhancement of reperfused irreversibly injured myocardium was delayed but increased steadily to a higher level than normal myocardium on IR-EPI. The reperfused irreversibly injured myocardium was identified on IR-EPI as a zone of high signal (hot spot). On GR-EPI, signal loss in reperfused irreversibly injured myocardium was significantly less compared with normally perfused myocardium. In animals with occlusive infarctions, there was no change in signal intensity over the ischemic region on either IR-EPI or GR-EPI. Occlusive infarction was identified as zones of either low (cold spot) or high (hot spot) signal compared with normal myocardium, depending on MR pulse sequence and dose of the contrast medium.
The transit of Gd-BOPTA/dimeg monitored by fast MR imaging techniques can be used to distinguish between reperfused reversibly and reperfused irreversibly injured myocardium and between occlusive and reperfused infarctions.
目前许多急性心肌梗死病例的治疗都涉及使用溶栓药物。对这种治疗方法的评估需要确定再灌注是否成功，以及评估再灌注区域梗死的存在情况和范围。本研究旨在通过大鼠模型模拟再灌注治疗的几种可能结果：（1）成功再灌注且无心肌梗死，（2）成功再灌注且有心肌梗死，（3）再灌注失败。研究了对比增强快速磁共振（MR）成像在确定再灌注成功方面的实用性。分别使用MR反转恢复回波平面成像（IR-EPI）和梯度回波回波平面成像（GR-EPI），研究了低剂量和高剂量钆布醇/葡甲胺（Gd-BOPTA/dimeg）对心肌信号的动态影响。
将大鼠分为以下几组：再灌注可逆性心肌损伤组（n = 9）、再灌注不可逆性心肌损伤组（n = 9）和闭塞性梗死组（n = 9）。在注射Gd-BOPTA/dimeg之前、期间和之后，每隔1或2秒采集一次MR回波平面图像。在所有组中，在团注峰值时，正常心肌信号在IR-EPI上急剧增加，在GR-EPI上降低，随后逐渐下降至基线。在再灌注可逆性心肌损伤的动物中，在Gd-BOPTA/dimeg通过期间和之后，正常区域和先前缺血区域无法区分。另一方面，再灌注不可逆损伤心肌的强化延迟，但在IR-EPI上稳定增加至高于正常心肌的水平。再灌注不可逆损伤心肌在IR-EPI上表现为高信号区（热点）。在GR-EPI上，再灌注不可逆损伤心肌的信号丢失明显少于正常灌注心肌。在闭塞性梗死的动物中，在IR-EPI或GR-EPI上，缺血区域的信号强度均无变化。根据MR脉冲序列和造影剂剂量，与正常心肌相比，闭塞性梗死表现为低信号区（冷点）或高信号区（热点）。
通过快速MR成像技术监测Gd-BOPTA/dimeg的通过情况，可用于区分再灌注可逆性和不可逆性损伤心肌，以及闭塞性梗死和再灌注梗死。
