Melin J A, Wijns W, Vanoverschelde J L, Heyndrickx G R
Division of Cardiology and of Nuclear Medicine, University of Louvain Medical School, Brussels, Belgium.
Cardiovasc Drugs Ther. 1994 May;8 Suppl 2:381-92. doi: 10.1007/BF00877323.
Nuclear cardiology techniques may be of help in evaluating the patient with symptoms of congestive heart failure and ventricular dysfunction in two respects: quantification of functional parameters by radionuclide angiography, and differentiation of viable from nonviable myocardium by perfusion and metabolic imaging. Left ventricular ejection fraction and volumes can be accurately assessed by equilibrium radionuclide angiography with a count-based method without any geometric assumptions. Indeed, because of its high reproducibility, this method is particularly suited for making sequential measurements in the same patient. The distinction between viable or reversible and scarred or irreversible dysfunctional myocardium can be made on the basis of myocardial perfusion, cell membrane integrity, and metabolic activity. Thallium myocardial imaging is used clinically to assess the first two parameters based on experimental data. Two clinical methods may be applied to the detection of viability: stress-redistribution-reinjection imaging or rest-redistribution imaging. In both of these, the severity of the reduction in thallium activity should be assessed to discriminate viable from nonviable myocardium. Stress-redistribution-reinjection thallium imaging should be the first approach, if possible, because inducible ischemia is a much more significant clinical variable in a patient with ventricular dysfunction in terms of management and risk assessment than is knowledge of myocardial viability. Positron emission tomography (PET) provides enhanced image resolution and correction for body attenuation, thereby overcoming the two major limitations of thallium imaging. In addition, it provides the capacity to quantitate regional blood flow and to assess regional metabolic activity independent of flow. Overall, the accuracies of thallium imaging (around 70%) and PET imaging (around 82%) are similar for the prediction of segmental changes after revascularization. However, in patients with poor global left ventricular function, the accuracy of PET seems to be better. Further studies are needed in a large number of patients evaluated for regional and global function to establish algorithms using thallium and PET imaging in dysfunctional myocardium. Dobutamine echocardiography should also be evaluated in these algorithms.
核心脏病学技术在评估有充血性心力衰竭症状和心室功能障碍的患者时，可能在两个方面有所帮助：通过放射性核素血管造影对功能参数进行量化，以及通过灌注和代谢成像区分存活心肌与无存活能力的心肌。左心室射血分数和容积可以通过平衡放射性核素血管造影采用基于计数的方法准确评估，无需任何几何假设。事实上，由于其高重复性，该方法特别适合在同一患者中进行连续测量。存活或可逆性功能障碍心肌与瘢痕或不可逆性功能障碍心肌之间的区分可以基于心肌灌注、细胞膜完整性和代谢活性来进行。铊心肌显像基于实验数据在临床上用于评估前两个参数。有两种临床方法可用于检测存活能力：负荷 - 再分布 - 再注射显像或静息 - 再分布显像。在这两种方法中，都应评估铊活性降低的严重程度，以区分存活心肌与无存活能力的心肌。如果可能的话，负荷 - 再分布 - 再注射铊显像应是首选方法，因为在心室功能障碍患者中，就管理和风险评估而言，诱发性缺血比心肌存活能力的知识是一个更重要的临床变量。正电子发射断层扫描（PET）提供了更高的图像分辨率并对身体衰减进行校正，从而克服了铊显像的两个主要局限性。此外，它能够定量局部血流量并独立于血流评估局部代谢活性。总体而言，铊显像（约70%）和PET显像（约82%）在预测血管重建术后节段性变化方面的准确性相似。然而，在左心室整体功能较差的患者中，PET的准确性似乎更好。需要对大量评估局部和整体功能的患者进行进一步研究，以建立在功能障碍心肌中使用铊和PET显像的算法。在这些算法中也应评估多巴酚丁胺超声心动图。
