Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
JACC Cardiovasc Imaging. 2010 Aug;3(8):797-805. doi: 10.1016/j.jcmg.2010.03.013.
The purpose of this study was to characterize the 3-dimensional structure of intravascular and extravascular microvessels during chronic total occlusion (CTO) maturation in a rabbit model.
Intravascular microchannels are an important component of a CTO and may predict guidewire crossability. However, temporal changes in the structure and geographic localization of these microvessels are poorly understood.
A total of 39 occlusions were created in a rabbit femoral artery thrombin model. Animals were sacrificed at 2, 6, 12, and 24 weeks (n > or =8 occlusions per time point). The arteries were filled with a low viscosity radio-opaque polymer compound (Microfil) at 150 mm Hg pressure. Samples were scanned in a micro-computed tomography system to obtain high-resolution volumetric images. Analysis was performed in an image processing package that allowed for labeling of multiple materials.
Two distinct types of microvessels were observed: circumferentially oriented "extravascular" and longitudinally oriented "intravascular" microvessels. Extravascular microvessels were evident along the entire CTO length and maximal at the 2-week time point. There was a gradual and progressive reduction in extravascular microvessels over time, with very minimal microvessels evident beyond 12 weeks. In contrast, intravascular microvessel formation was delayed, with peak vascular volume at 6 weeks, followed by modest reductions at later time points. Intravascular microvessel formation was more prominent in the body compared with that in the proximal and distal ends of the CTO. Sharply angulated connections between the intravascular and extravascular microvessels were present at all time points, but most prominent at 6 weeks. At later time points, the individual intravascular microvessels became finer and more tortuous, although the continuity of these microvessels remained constant beyond 2 weeks.
Differences are present in the temporal and geographic patterns of intravascular and extravascular microvessel formation during CTO maturation.
本研究旨在通过兔模型来描述慢性完全闭塞（CTO）成熟过程中血管内和血管外微血管的三维结构。
血管内微通道是 CTO 的一个重要组成部分，可能可以预测导丝的可穿透性。然而，这些微血管的结构和地理定位的时间变化尚不清楚。
在兔股动脉凝血酶模型中总共创建了 39 个闭塞。动物在 2、6、12 和 24 周时处死（每个时间点>或=8 个闭塞）。动脉在 150mmHg 压力下用低粘度射线可透性聚合物化合物（Microfil）填充。样品在微计算机断层扫描系统中进行扫描，以获得高分辨率体积图像。在一个图像处理软件包中进行分析，该软件包允许对多种材料进行标记。
观察到两种不同类型的微血管：环形排列的“血管外”和纵向排列的“血管内”微血管。血管外微血管在整个 CTO 长度上都很明显，在 2 周时间点时达到最大值。随着时间的推移，血管外微血管逐渐减少，12 周后几乎没有微血管。相比之下，血管内微血管的形成是延迟的，血管容积峰值出现在 6 周时，随后在以后的时间点略有减少。血管内微血管的形成在 CTO 的体部比在近侧和远侧更明显。在所有时间点都存在血管内和血管外微血管之间的锐角连接，但在 6 周时最为明显。在以后的时间点，单独的血管内微血管变得更细且更迂曲，尽管这些微血管的连续性在 2 周后保持不变。
在 CTO 成熟过程中，血管内和血管外微血管的形成在时间和空间模式上存在差异。
