Marwan Mohamed, Hell Michaela, Schuhbäck Annika, Gauss Sören, Bittner Daniel, Pflederer Tobias, Achenbach Stephan
From the Department of Cardiology, University of Erlangen, Germany.
J Comput Assist Tomogr. 2017 Sep/Oct;41(5):762-767. doi: 10.1097/RCT.0000000000000589.
The factors influencing genesis of atherosclerosis at specific regions within the coronary arterial system are currently uncertain. Local mechanical factors such as shear stress as well as metabolic factors, including inflammatory mediators released from epicardial fat, have been proposed. We analyzed computed tomographic (CT) attenuation of pericoronary adipose tissue in normal versus atherosclerotic coronary segments as defined by intravascular ultrasound (IVUS).
We evaluated the data sets of 29 patients who were referred for invasive coronary angiography and in whom IVUS of 1 coronary vessel was performed for clinical reasons. Coronary CT angiography was performed within 24 hours from invasive coronary angiography. Computed tomographic angiography was performed using dual-source CT (Siemens Healthcare; Forchheim, Germany). A contrast-enhanced volume data set was acquired (120 kV, 400 mA/rot, collimation 2 × 64 × 0.6 mm, 60-80 mL intravenous contrast agent). Intravascular ultrasound was performed using a 40-MHz IVUS catheter (Atlantis; Boston Scientific Corporation, Natick, Mass) and motorized pullback at 0.5 mm/s. Sixty corresponding coronary artery segments within the coronary artery system were identified in both dual source computed tomography and IVUS using bifurcation points as fiducial markers. In dual source computed tomography data sets, 8 serial parallel cross sections (2-mm slice thickness) were rendered orthogonal to the center line of the coronary artery for each segment. For each cross section, pericoronary adipose tissue within a radius of 3 mm from the coronary artery and enclosed within the epicardium (excluding coronary veins and myocardium) was manually traced and mean CT attenuation values were obtained. Intravascular ultrasound was used to define coronary segments as follows: presence of predominantly fibrous atherosclerotic plaque (hyperechoic), presence of predominantly lipid-rich atherosclerotic plaque (hypoechoic), and absence of atherosclerotic plaque.
In IVUS, 20 coronary segments with fibrous plaque, 20 segments with lipid-rich plaque, and 20 coronary segments without plaque were identified. The mean CT attenuation of pericoronary adipose tissue for segments with any coronary atherosclerotic plaque was -34 ± 14 Hounsfield units (HU), as compared with -56 ± 16 HU for segments without plaque (P = 0.005). The density of pericoronary fat in segments with fibrous versus lipid-rich plaque as defined by IVUS was not significantly different (-35 ± 19 HU vs -36 ± 16 HU, P = 0.8).
Mean CT attenuation of pericoronary adipose tissue is significantly lower for normal versus atherosclerotic coronary segments. This supports a hypothesis of different types of pericoronary adipose tissue, the more metabolically active of which might exert local effects on the coronary vessels, thus contributing to atherogenesis.
目前尚不清楚影响冠状动脉系统特定区域动脉粥样硬化发生的因素。有人提出了局部机械因素，如剪切应力，以及代谢因素，包括心外膜脂肪释放的炎症介质。我们分析了血管内超声（IVUS）定义的正常与动脉粥样硬化冠状动脉节段周围冠状动脉脂肪组织的计算机断层扫描（CT）衰减情况。
我们评估了29例因侵入性冠状动脉造影而就诊的患者的数据集，出于临床原因对其中1支冠状动脉进行了IVUS检查。在侵入性冠状动脉造影后24小时内进行冠状动脉CT血管造影。使用双源CT（西门子医疗；德国福希海姆）进行计算机断层血管造影。获取增强对比剂的容积数据集（120 kV，400 mA/旋转，准直2×64×0.6 mm，60 - 80 mL静脉注射造影剂）。使用40 MHz的IVUS导管（Atlantis；波士顿科学公司，马萨诸塞州纳蒂克）进行血管内超声检查，并以0.5 mm/s的速度进行电动回撤。在双源计算机断层扫描和IVUS中，以分叉点作为基准标记，在冠状动脉系统中识别出60个相应的冠状动脉节段。在双源计算机断层扫描数据集中，为每个节段生成8个连续的平行横截面（切片厚度2 mm），使其与冠状动脉中心线正交。对于每个横截面，手动追踪距冠状动脉3 mm半径范围内且包绕在心外膜内（不包括冠状静脉和心肌）的冠状动脉周围脂肪组织，并获得平均CT衰减值。血管内超声用于将冠状动脉节段定义如下：主要为纤维性动脉粥样硬化斑块（高回声）、主要为富含脂质的动脉粥样硬化斑块（低回声）以及无动脉粥样硬化斑块。
在IVUS检查中，识别出20个有纤维斑块的冠状动脉节段、20个有富含脂质斑块的节段和20个无斑块的冠状动脉节段。任何冠状动脉粥样硬化斑块节段的冠状动脉周围脂肪组织平均CT衰减值为 - 34±14亨氏单位（HU），而无斑块节段为 - 56±16 HU（P = 0.005）。IVUS定义的有纤维斑块与富含脂质斑块节段的冠状动脉周围脂肪密度无显著差异（ - 35±19 HU对 - 36±16 HU，P = 0.8）。
正常冠状动脉节段与动脉粥样硬化冠状动脉节段相比，冠状动脉周围脂肪组织的平均CT衰减值明显更低。这支持了关于不同类型冠状动脉周围脂肪组织的假说其中代谢活性更高的脂肪组织可能对冠状动脉产生局部影响，从而促进动脉粥样硬化的发生。
