Beiki D, Fallahi B, Mohseni Z, Khalaj A, Fard-Esfahani A, Eftekhari M
Research Institute for Nuclear Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Nuklearmedizin. 2010;49(1):19-27. doi: 10.3413/nukmed-0266.
Some studies reported that 99mTc-MIBI may redistribute in ischaemic myocardium and this phenomenon may have potential role for better assessment of viability by delayed 99mTc-MIBI imaging. Some studies also suggested that infusion of low dose dobutamine during delayed imaging may enhance the value of 99mTc-MIBI imaging for evaluation of viability. The aim of this study is to determine whether the observed changes of perfusion defects on delayed images are caused by early radiotracer redistribution or as a result of reversal partial volume effect secondary to inotropic stimulation.
PATIENTS, METHODS: 89 patients with angiographically proven coronary artery disease (CAD) were enrolled in this randomized clinical trial study. In all cases, gated-SPECT images were obtained 60 minutes after stress with dipyridamole injection. Subsequently the patients were randomly allocated in two groups and the second imaging was performed at 120th minute during low dose dobutamine (dobutamine group; 45 cases) or placebo infusion (placebo group; 44 cases). Difference between summed stress score of the first (SSS1) and second (SSS2) stress images (DeltaSSS) was considered as a marker of reversibility in single-injection double-acquisition (SIDA) protocol. Also summed difference score (SDS) was recorded as a marker of reversibility in standard stress/rest, double-injection double-acquisition (DIDA) protocol. DeltaSSS of the two studied groups were compared. Also the correlation and agreement between DeltaSSS and SDS were analyzed.
A significant difference was found between SSS1 (median 15, range 0-48) and SSS2 (median 11, range 0-42) in total patients (p < 0.0001). A significant correlation was noted between DeltaSSS and SDS in dobutamine group (r = 0.58, p = 0.002) as well as in placebo group (r = 0.57, p < 0.0001). Considering DIDA protocol as a standard reference method, the influence of dobutamine infusion was not shown to be significantly different from the placebo effect on the magnitude of fixed or reversible perfusion defects in SIDA protocol.
The changes in the magnitude of the perfusion defects may occur in the first hours of 99mTc-MIBI injection in the stress phase imaging. These changes correlate well and are in agreement with perfusion improvement on the rest images. This phenomenon may be independent of improvement in myocardial function, in more delayed imaging or following inotropic augmentation, and thus is likely due to 99mTc-MIBI redistribution. This may open new technical and clinical aspects and potentials for 99mTc-MIBI imaging.
一些研究报告称，99mTc-MIBI可能在缺血心肌中重新分布，这种现象可能对通过延迟99mTc-MIBI显像更好地评估心肌存活性具有潜在作用。一些研究还表明，在延迟显像期间输注低剂量多巴酚丁胺可能会提高99mTc-MIBI显像评估心肌存活性的价值。本研究的目的是确定延迟图像上观察到的灌注缺损变化是由早期放射性示踪剂重新分布引起的，还是由正性肌力刺激继发的反向部分容积效应导致的。
患者、方法：89例经血管造影证实患有冠状动脉疾病（CAD）的患者纳入了这项随机临床试验研究。在所有病例中，在注射双嘧达莫进行负荷试验60分钟后获得门控单光子发射计算机断层显像（SPECT）图像。随后，将患者随机分为两组，在第120分钟进行第二次显像，其中一组输注低剂量多巴酚丁胺（多巴酚丁胺组；45例），另一组输注安慰剂（安慰剂组；44例）。第一次（SSS1）和第二次（SSS2）负荷图像的总负荷评分差值（DeltaSSS）被视为单注射双采集（SIDA）方案中可逆性的标志物。同时，记录总差值评分（SDS）作为标准负荷/静息双注射双采集（DIDA）方案中可逆性的标志物。比较两组研究对象的DeltaSSS。此外，分析DeltaSSS与SDS之间的相关性和一致性。
所有患者的SSS1（中位数15，范围0 - 48）和SSS2（中位数11，范围0 - 42）之间存在显著差异（p < 0.0001）。多巴酚丁胺组（r = 0.58，p = 0.002）以及安慰剂组（r = 0.57，p < 0.0001）的DeltaSSS与SDS之间均存在显著相关性。将DIDA方案视为标准参考方法，在SIDA方案中，多巴酚丁胺输注对固定或可逆灌注缺损大小的影响与安慰剂效应相比无显著差异。
在负荷显像阶段注射99mTc-MIBI后的最初几个小时内，灌注缺损大小可能会发生变化。这些变化与静息图像上的灌注改善具有良好的相关性和一致性。这种现象可能与心肌功能改善无关，在更延迟的显像或正性肌力增强后出现，因此可能是由于99mTc-MIBI重新分布所致。这可能为99mTc-MIBI显像开启新的技术和临床方面及潜力。
