MYOCARDIAL VIABILITY IN CORONARY ARTERY DISEASE AND LEFT VENTRICULAR DYSFUNCTION

在许多冠心病(CAD)患者中，左侧受损 心脏(LV)功能是在局部缺血或 冬眠心肌而不是不可逆转的心肌梗死。 我们之前已经证明了铊-201闪烁照相术(使用 应力重分布-再注入方案)是一种准确的方法 确定功能不全但仍可存活的心肌区域，由 正电子发射断层扫描保存代谢活性的证据 (PET)和心肌梗死后局部功能的改善 血运重建。这些发现在过去的一年里得到了扩展 通过4个系列的调查。1)利用门控自旋回波的研究 磁共振成像(MRI)评价局部舒张期末期壁 厚度和收缩期壁增厚证实这些区域 通过铊摄取确定为可行的，保存了管壁增厚。 2.)我们还表明，静态注射的铊(通过成像) 最初和在4小时再分发期之后)也是有价值的 与结果相比较识别存活心肌的技术 正电子发射计算机断层扫描和核磁共振成像。3.)我们已经证明了具有平行关系的地区 血流量和葡萄糖利用减少(通过摄取来衡量 的F-脱氧葡萄糖或FDG保存了壁增厚，如 只要FDG活性下降不严重即可。因此，具有以下特征的区域 血流减少不一定表现为相对于血流的FDG摄取增强 (称为FDG-血流“不匹配”)被确定为可行的，以及 新陈代谢缺陷的严重性必须在 应用正电子发射计算机断层扫描评价存活心肌。4.)我们已经展示了 局部血流正常的FDG摄取减少的区域 (其他调查人员认为这是“正常”的发现) 主要发生在受损害的心肌区域 可逆性缺血。这种代谢缺陷的原因，导致 减少而不是增加葡萄糖摄取，仍有待澄清。

In many patients with coronary artery disease (CAD), impaired left ventricular (LV) function arises on the basis of regionally ischemic or hibernating myocardium rather than irreversibly infarcted myocardium. We have previously demonstrated that thallium-201 scintigraphy (using a stress-redistribution-reinjection protocol) is an accurate method to identify dysfunctional but viable myocardial regions, as verified by evidence of preserved metabolic activity by positron emission tomography (PET) and by improved regional function after myocardial revascularization.These findings have been extended during the past year by 4 series of investigations. 1.) Studies employing gated spin echo magnetic resonance imaging (MRI) to assess regional end-diastolic wall thickness and systolic wall thickening have confirmed that regions identified as viable by thallium uptake have preserved wall thickening. 2.) We have also shown that thallium injected at rest (with imaging initially and after a 4 hour redistribution period) is also a valuable technique for identifying viable myocardium in comparison to the results of both PET and MRI. 3.) We have demonstrated that regions with parallel reduction in blood flow and glucose utilization (as measured by uptake of (18)F-fluorodeoxyglucose, or FDG have preserved wall thickening, as long as the reduction in FDG activity is not severe. Thus, regions with reduced blood flow need not manifest enhanced FDG uptake relative to flow (termed the FDG-blood flow "mismatch") to be identified as viable, and the severity of the metabolic defect must be taken into consideration in the assessment of viable myocardium using PET imaging. 4.) We have shown that regions with reduced FDG uptake with normal regional blood flow (considered a "normal" finding by other investigators) occurs predominantly in regions of jeopardized myocardium capable of undergoing reversible ischemia. The cause of this metabolic defect, leading to reduced rather than enhanced glucose uptake, remains to be clarified.