Christiaan Barnard Department of Cardiothoracic Surgery, University of Cape Town, Cape Town, South Africa.
J Vasc Surg. 2012 Jun;55(6):1734-41. doi: 10.1016/j.jvs.2011.11.057. Epub 2012 Mar 2.
Flow patterns and shear forces in native coronary arteries are more protective against neointimal hyperplasia than those in femoral arteries. Yet, the caliber mismatch with their target arteries makes coronary artery bypass grafts more likely to encounter intimal hyperplasia than their infrainguinal counterparts due to the resultant slow flow velocity and decreased wall stress. To allow a site-specific, flow-related comparison of remodeling behavior, saphenous vein bypass grafts were simultaneously implanted in femoral and coronary positions.
Saphenous vein grafts were concomitantly implanted as coronary and femoral bypass grafts using a senescent nonhuman primate model. Duplex ultrasound-based blood flow velocity profiles and vein graft and target artery dimensions were correlated with dimensional and histomorphologic graft remodeling in large, senescent Chacma baboons (n = 8; 28.1 ± 4.9 kg) during a 24-week period.
At implantation, the cross-sectional quotient (Q(c)) between target arteries and vein grafts was 0.62 ± 0.10 for femoral grafts vs 0.17 ± 0.06 for coronary grafts, resulting in a dimensional graft-to-artery mismatch 3.6 times higher (P < .0001) in coronary grafts. Together with different velocity profiles, these site-specific dimensional discrepancies resulted in a 57.9% ± 19.4% lower maximum flow velocity (P = .0048), 48.1% ± 23.6% lower maximal cycling wall shear stress (P = .012), and 62.2% ± 21.2% lower mean velocity (P = .007) in coronary grafts. After 24 weeks, the luminal diameter of all coronary grafts had contracted by 63%, from an inner diameter of 4.49 ± 0.60 to 1.68 ± 0.63 mm (P < .0001; subintimal diameter: -41.5%; P = .002), whereas 57% of the femoral interposition grafts had dilated by 31%, from 4.21 ± 0.25 to 5.53 ± 1.30 mm (P = .020). Neointimal tissue was 2.3 times thicker in coronary than in femoral grafts (561 ± 73 vs 240 ± 149 μm; P = .001). Overall, the luminal area of coronary grafts was an average of 4.1 times smaller than that of femoral grafts.
Although coronary and infrainguinal bypass surgery uses saphenous veins as conduits, they undergo significantly different remodeling processes in these two anatomic positions.
与股动脉相比，原生冠状动脉中的血流模式和剪切力更能防止内膜增生。然而，由于吻合口处血流速度较慢，壁面切应力降低，其与靶血管的口径不匹配使得冠状动脉旁路移植术更容易发生内膜增生，比其在下肢的对应部位更容易发生。为了实现对重塑行为的特定部位、与血流相关的比较，我们同时在股动脉和冠状动脉部位植入了大隐静脉旁路移植。
我们使用衰老的非人灵长类动物模型，同时将大隐静脉旁路移植作为冠状动脉和股动脉旁路移植。在 28.1 ± 4.9 kg 的衰老喀拉哈里大狒狒中，在 24 周的时间内，通过基于双功能超声的血流速度剖面和静脉移植物和靶动脉的尺寸，对大隐静脉旁路移植在大隐静脉旁路移植中的大小和形态重塑进行了相关分析。
在植入时，股动脉旁路移植的靶动脉与静脉移植物的横截面积比（Q(c)）为 0.62 ± 0.10，而冠状动脉旁路移植的 Q(c)为 0.17 ± 0.06，导致冠状动脉旁路移植的血管到血管的尺寸不匹配高 3.6 倍（P <.0001）。再加上不同的速度剖面，这些特定部位的尺寸差异导致冠状动脉旁路移植的最大流速降低了 57.9% ± 19.4%（P =.0048），最大循环壁面剪切应力降低了 48.1% ± 23.6%（P =.012），平均流速降低了 62.2% ± 21.2%（P =.007）。24 周后，所有冠状动脉旁路移植的管腔直径均收缩了 63%，从 4.49 ± 0.60 毫米缩小至 1.68 ± 0.63 毫米（P <.0001；内膜下直径：-41.5%；P =.002），而 57%的股间置旁路移植的直径扩大了 31%，从 4.21 ± 0.25 毫米扩大至 5.53 ± 1.30 毫米（P =.020）。与股动脉旁路移植相比，冠状动脉旁路移植的新生内膜组织厚 2.3 倍（561 ± 73 与 240 ± 149 μm；P =.001）。总体而言，冠状动脉旁路移植的管腔面积平均比股动脉旁路移植小 4.1 倍。
尽管冠状动脉和下肢旁路手术都使用大隐静脉作为移植物，但在这两个解剖部位，它们经历了显著不同的重塑过程。
