Leon A R, Eisner R L, Martin S E, Schmarkey L S, Aaron A M, Boyers A S, Burnham K M, Oh D J, Patterson R E
Carlyle Fraser Heart Center, Crawford Long Hospital of Emory University, Atlanta, Georgia 30365.
J Am Coll Cardiol. 1992 Dec;20(7):1612-25. doi: 10.1016/0735-1097(92)90458-y.
The purpose of the present study was to compare single-photon emission computed tomographic (SPECT) myocardial images of technetium-99m (Tc-99m) sestamibi and thallium-201 (Tl-201) isotopes in the same dog undergoing partial coronary occlusion during pharmacologic vasodilation.
To date, no controlled study has been reported comparing SPECT Tc-99m sestamibi with SPECT Tl-201 imaging during stress with anatomic and physiologic standards.
Mongrel dogs were anesthetized with chloralose and instrumented to record left anterior descending coronary blood flow and aortic pressure. Partial coronary occlusion with a hydraulic cuff reduced coronary vascular conductance, which is equal to the coronary blood flow normalized to aortic pressure during peak vasodilation with intravenous adenosine. Each dog received 5 mCi of Tl-201, then 30 mCi of Tc-99m sestamibi during partial coronary occlusion at peak vasodilation. Tomographic myocardial imaging was performed in a 180 degrees anterior arc scan for 33.5 min, first with Tl-201, and later, without moving the dog, for 33.5 min with Tc-99m sestamibi. Postmortem staining defined the region underperfused because of its dependence on the artery that was partially occluded.
In seven dogs with moderate reduction in coronary blood flow, coronary vascular conductance decreased with partial coronary occlusion (47 +/- 12%) during Tl-201 imaging and (47 +/- 8%, p = NS) during Tc-99m sestamibi imaging. The underperfused region was 23.9 +/- 6.4% of total left ventricular mass. Counts in the defects were 39% higher (0.86 +/- 0.08 of normal counts) for Tc-99m sestamibi than for Tl-201 (0.64 +/- 0.09 of normal counts, p < 0.001), and the defect on SPECT Tc-99m sestamibi images occupied only a fraction (0.37 +/- 0.30) of the area of the defect on the Tl-201 images of the same dog. Bull's-eye displays constructed from the pathologic slices showed that the Tl-201 defect size was closer to the underperfused region of the left ventricular mass determined pathologically than was the Tc-99m sestamibi defect size. In four additional dogs a severe, near total coronary occlusion was created during Tl-201 and Tc-99m sestamibi administration. In these dogs, similar defect contrast (0.55 +/- 0.12 vs. 0.62 +/- 0.09, p = NS) and areas (0.18 +/- 0.07 vs. 0.18 +/- 0.11, p = NS) were observed with Tl-201 and Tc-99m sestamibi, respectively.
Tomographic myocardial imaging with Tc-99m sestamibi during moderately severe partial coronary occlusion underestimated the area of the defect relative to Tl-201 or to the pathologic reference standard in dogs. Defect contrast was sharper with tomographic myocardial Tl-201 than with tomographic myocardial Tc-99m sestamibi during moderately severe partial coronary occlusion.
本研究的目的是比较在同一犬类进行药物性血管舒张期间部分冠状动脉闭塞时，锝-99m（Tc-99m）甲氧基异丁基异腈和铊-201（Tl-201）同位素的单光子发射计算机断层扫描（SPECT）心肌图像。
迄今为止，尚无对照研究报道在应激状态下将SPECT Tc-99m甲氧基异丁基异腈与SPECT Tl-201成像与解剖学和生理学标准进行比较。
用氯醛糖麻醉杂种犬，并安装仪器记录左前降支冠状动脉血流和主动脉压力。用水力袖带进行部分冠状动脉闭塞可降低冠状动脉血管传导性，其等于在静脉注射腺苷进行最大血管舒张时归一化至主动脉压力的冠状动脉血流。每只犬在部分冠状动脉闭塞且血管舒张达到峰值时，先接受5毫居里的Tl-201，然后接受30毫居里的Tc-99m甲氧基异丁基异腈。在180度前弧扫描中进行断层心肌成像33.5分钟，先使用Tl-201，然后在不移动犬的情况下，使用Tc-99m甲氧基异丁基异腈进行33.5分钟成像。死后染色确定了由于依赖于部分闭塞的动脉而灌注不足的区域。
在7只冠状动脉血流中度减少的犬中，冠状动脉血管传导性在Tl-201成像期间随部分冠状动脉闭塞而降低（47±12%），在Tc-99m甲氧基异丁基异腈成像期间降低（47±8%，p=无显著性差异）。灌注不足区域占左心室总质量的23.9±6.4%。Tc-99m甲氧基异丁基异腈在缺损处的计数比Tl-201高39%（为正常计数的0.86±0.08）（为正常计数的0.64±0.09，p<0.001），并且同一犬的SPECT Tc-99m甲氧基异丁基异腈图像上的缺损仅占Tl-201图像上缺损面积的一小部分（0.37±0.30）。根据病理切片构建的靶心图显示，Tl-201缺损大小比Tc-99m甲氧基异丁基异腈缺损大小更接近病理确定的左心室质量灌注不足区域。在另外4只犬中，在给予Tl-201和Tc-99m甲氧基异丁基异腈期间造成了严重的、近乎完全的冠状动脉闭塞。在这些犬中，分别用Tl-201和Tc-99m甲氧基异丁基异腈观察到相似的缺损对比度（0.55±0.12对0.62±0.09，p=无显著性差异）和面积（0.18±0.07对0.18±0.11，p=无显著性差异）。
在犬类中，在中度严重的部分冠状动脉闭塞期间用Tc-99m甲氧基异丁基异腈进行断层心肌成像相对于Tl-201或病理参考标准低估了缺损面积。在中度严重的部分冠状动脉闭塞期间，断层心肌Tl-201的缺损对比度比断层心肌Tc-99m甲氧基异丁基异腈更清晰。
