Dilsizian V, Freedman N M, Bacharach S L, Perrone-Filardi P, Bonow R O
Cardiology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
Circulation. 1992 Feb;85(2):627-34. doi: 10.1161/01.cir.85.2.627.
Thallium reinjection immediately after stress-redistribution imaging identifies ischemic but viable myocardium in as many as 50% of the regions characterized by conventional redistribution imaging as irreversibly injured. However, we have previously shown that some regions in which irreversible defects persist despite reinjection are metabolically active, and hence viable, by positron emission tomography. In the current study, we determined whether the severity of reduction in thallium activity within irreversible defects on redistribution images and the magnitude of change in regional thallium activity after reinjection can further discriminate viable from nonviable myocardium in such defects.
We studied 150 patients with coronary artery disease by exercise thallium tomography using the rest-reinjection protocol. The three sets of images (stress, redistribution, and reinjection) were then analyzed quantitatively. The increase in regional thallium activity from redistribution to reinjection was computed, normalized to the increase observed in a normal region, and termed "differential uptake." Of the 175 myocardial regions designated to have irreversible thallium defects on conventional 3-4 hour redistribution images, 132 had only mild-to-moderate reduction in thallium activity (51-85% of normal activity), and 43 had severe reduction in thallium activity (less than or equal to 50% of normal activity). Thallium reinjection resulted in enhanced relative activity in 60 of 132 (45%) of the mild-to-moderate irreversible defects and 22 of 43 (51%) of the severe irreversible defects, leaving roughly half of these defects remaining irreversible after reinjection. However, in regions that appeared to remain irreversible despite reinjection, the magnitude of differential uptake differed between mild-to-moderate (74 +/- 14%) and severe (35 +/- 16%) irreversible defects (p less than 0.001). All regions with mild-to-moderate defects demonstrated greater than 50% differential uptake after reinjection. In contrast, all except two of the regions with severe irreversible defects demonstrated differential uptake of less than 50%. Fifteen patients also underwent positron emission tomography at rest with 18F-fluorodeoxyglucose (FDG) and 15O-water. FDG uptake was present in 91% of regions with mild-to-moderate reduction in thallium activity, and the results of differential uptake and FDG data were concordant in 81% of these regions.
These data indicate that the magnitude of thallium uptake after reinjection differs between mild-to-moderate and severe irreversible defects on standard 3-4 hour redistribution images. The substantial differential uptake of thallium (greater than 50%) after reinjection in mild-to-moderate defects, even when relative thallium activity does not increase appreciably (and the defect appears to remain irreversible), coupled with preserved metabolic activity by positron emission tomography, supports the concept that such mild-to-moderate irreversible defects represent viable myocardium.
负荷 - 再分布显像后立即进行铊再注射，可识别出在传统再分布显像中被判定为不可逆损伤的区域中多达50%的缺血但存活的心肌。然而，我们之前已经表明，尽管再注射后仍存在不可逆缺损的一些区域，通过正电子发射断层扫描显示其代谢活跃，因此是存活的。在本研究中，我们确定了再分布图像上不可逆缺损内铊活性降低的严重程度以及再注射后区域铊活性的变化幅度是否能进一步区分此类缺损中存活与非存活的心肌。
我们采用静息 - 再注射方案，通过运动铊断层扫描研究了150例冠心病患者。然后对三组图像（负荷、再分布和再注射）进行定量分析。计算从再分布到再注射区域铊活性的增加量，并将其归一化到正常区域观察到的增加量，称为“差异摄取”。在传统的3 - 4小时再分布图像上被判定为有不可逆铊缺损的175个心肌区域中，132个区域的铊活性仅有轻度至中度降低（为正常活性的51% - 85%），43个区域的铊活性严重降低（小于或等于正常活性的50%）。铊再注射使132个轻度至中度不可逆缺损中的60个（45%）和43个严重不可逆缺损中的22个（51%）的相对活性增强，再注射后这些缺损中约一半仍为不可逆。然而，在尽管再注射后仍似乎为不可逆的区域中，轻度至中度（74±14%）和严重（35±16%）不可逆缺损的差异摄取幅度不同（p＜0.001）。所有轻度至中度缺损的区域在再注射后差异摄取均大于50%。相比之下，除两个区域外，所有严重不可逆缺损的区域差异摄取均小于50%。15例患者还在静息状态下接受了18F - 氟脱氧葡萄糖（FDG）和15O - 水的正电子发射断层扫描。铊活性轻度至中度降低的区域中91%存在FDG摄取，这些区域中81%的差异摄取结果与FDG数据一致。
这些数据表明，在标准的3 - 4小时再分布图像上，轻度至中度和严重不可逆缺损再注射后铊摄取的幅度不同。轻度至中度缺损再注射后铊的大量差异摄取（大于50%），即使相对铊活性没有明显增加（且缺损似乎仍为不可逆），再加上正电子发射断层扫描显示的代谢活性保留，支持了这样一种观点，即此类轻度至中度不可逆缺损代表存活心肌。
