Fallavollita J A, Brody A S, Bunnell I L, Kumar K, Canty J M
Department of Medicine, State University of New York, Buffalo School of Biomedical Sciences.
Circulation. 1994 Jan;89(1):285-90. doi: 10.1161/01.cir.89.1.285.
The predominant cause of coronary artery calcification is atherosclerosis. Although fast x-ray computed tomography (CT) has been demonstrated to be a sensitive technique to detect coronary calcification, the increasing prevalence of calcification with age has been associated with a low specificity for identifying obstructive atherosclerosis. We hypothesized that the specificity of this test would be improved in a younger patient population, making it more useful in the diagnosis of coronary artery disease.
We compared fast CT-detected calcification with coronary angiography in 106 patients under the age of 50 years. Nonenhanced fast CT scans consisting of 20 contiguous 3-mm tomograms of the proximal coronary arteries were obtained during a single breath hold. A positive scan was defined as 4 contiguous voxels (> or = 1 mm2) of density > 130 Hounsfield units in the region of the epicardial coronary arteries. Calcification detected by fast CT had an 85% sensitivity to predict patients with significant coronary artery disease (> or = 50% diameter stenosis), with a specificity of 45%. Although the sensitivity to detect multivessel disease was 94%, the sensitivity to detect single-vessel disease was 75%. Changing the threshold for defining a positive fast CT scan from 4 to 2 contiguous voxels produced a small improvement in sensitivity, to 88%, but reduced specificity to 36%.
Although the specificity to detect angiographically significant coronary disease with fast CT improves in a younger patient population, it continues to be relatively low. In contrast to older patient populations, a small but significant number of patients < 50 years old with angiographically significant coronary artery disease do not have coronary calcification demonstrated by fast CT. Thus, caution should be used in excluding significant coronary artery disease on the basis of a negative fast CT study.
冠状动脉钙化的主要原因是动脉粥样硬化。尽管快速X线计算机断层扫描（CT）已被证明是检测冠状动脉钙化的敏感技术，但随着年龄增长钙化患病率的增加与识别阻塞性动脉粥样硬化的低特异性相关。我们推测该检查在年轻患者人群中的特异性会提高，使其在冠状动脉疾病的诊断中更有用。
我们在106例50岁以下患者中比较了快速CT检测的钙化与冠状动脉造影结果。在一次屏气期间获取由近端冠状动脉的20个连续3毫米断层图像组成的非增强快速CT扫描。阳性扫描定义为在心外膜冠状动脉区域有4个连续体素（≥1平方毫米）密度>130亨氏单位。快速CT检测到的钙化对预测患有严重冠状动脉疾病（直径狭窄≥50%）的患者有85%的敏感性，特异性为45%。虽然检测多支血管疾病的敏感性为94%，但检测单支血管疾病的敏感性为75%。将定义阳性快速CT扫描的阈值从4个连续体素改为2个连续体素使敏感性略有提高，至88%，但特异性降至36%。
尽管快速CT检测血管造影显示的严重冠状动脉疾病在年轻患者人群中的特异性有所提高，但仍然相对较低。与老年患者人群不同，一小部分但数量可观的50岁以下患有血管造影显示严重冠状动脉疾病的患者，快速CT未显示冠状动脉钙化。因此，基于快速CT检查阴性排除严重冠状动脉疾病时应谨慎。
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