Weinstein H, Reinhardt C P, Leppo J A
Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester, USA.
J Nucl Med. 1998 Apr;39(4):598-607.
Conventional perfusion scintigraphy assesses disparities in regional myocardial blood flow but does not directly detect hypoxic tissue. Nitroimidazoles labeled with positron-emitting radionuclides have recently shown promise as direct markers of myocardial hypoxia. This study evaluates a new 99mTc-labeled nitroimidazole of potential benefit in standard myocardial scintigraphy.
Technetium-99m-labeled nitroimidazole was administered to rabbits during the early reperfusion phase after 10 min (Group 1) or 60 (Group 2) min of coronary occlusion or after 10 min of a fixed coronary occlusion (Group 3). Tracer retention at 1 hr was assessed in relation to microsphere-determined blood flow during coronary occlusion and at tracer injection. The pattern of nitroimidazole retention on autoradiographs was then compared with the pattern of myocardial hypoperfusion defined by fluorescein photography to precisely define tracer localization.
The retention of nitroimidazole in Group 1 rabbits (brief occlusion) was independent of both occlusion and reperfusion blood flow and was uniformly distributed on the autoradiographs. In contrast, nitroimidazole retention in Groups 2 and 3 increased with the severity of hypoperfusion during the occlusion phase and precisely delineated the ischemic zone on all autoradiographs.
This 99mTc-labeled hypoxia-avid tracer delineates severe ischemia even after blood flow to the compromised myocardium has been restored. This class of compounds can potentially enhance the physiological assessment of patients with ischemic heart disease.
传统灌注闪烁显像可评估局部心肌血流差异，但不能直接检测缺氧组织。最近，用发射正电子放射性核素标记的硝基咪唑显示出有望成为心肌缺氧的直接标志物。本研究评估一种新型的99mTc标记硝基咪唑在标准心肌闪烁显像中的潜在益处。
在冠状动脉闭塞10分钟（第1组）或60分钟（第2组）后的早期再灌注阶段，或在固定冠状动脉闭塞10分钟后（第3组），给兔子注射99mTc标记的硝基咪唑。在冠状动脉闭塞期间及注射示踪剂时，根据微球测定的血流情况评估1小时时示踪剂的滞留情况。然后将放射自显影片上硝基咪唑的滞留模式与荧光素摄影定义的心肌灌注不足模式进行比较，以精确确定示踪剂的定位。
第1组兔子（短暂闭塞）中硝基咪唑的滞留与闭塞和再灌注血流均无关，且在放射自显影片上均匀分布。相比之下，第2组和第3组中硝基咪唑的滞留随着闭塞期灌注不足的严重程度增加，并且在所有放射自显影片上精确勾勒出缺血区域。
这种99mTc标记的亲缺氧示踪剂即使在受损心肌的血流恢复后仍能勾勒出严重缺血情况。这类化合物可能会增强对缺血性心脏病患者的生理评估。
