Hokkaido University, 064-0821, Sapporo, Hokkaido N-1W-25, Japan.
Kansai University, Suita, Osaka, Japan.
Adv Exp Med Biol. 2014;812:317-323. doi: 10.1007/978-1-4939-0620-8_42.
Forced retrograde perfusion through the venous system with arterial blood can provide adequate oxygen to peripheral tissues at rest through veno-capillary networks which is the basis for surgical restoration of blood flow by distal vein arterialization (DVA). To be successful such surgery requires disruption of valve leaflets in the veins, which can be accomplished easily in the larger vessels. However, the smallest veins (venules) of less than 100 μm in diameter, also possess valves, are distributed widely throughout all tissues and are too fine for any effective surgical interference. Thus venular valves cannot be disrupted or dissected with presently available technology. Nevertheless, clinical observations suggest that retrograde peripheral blood flow is rapidly established after DVA surgery. There is as yet no rational explanation for this phenomenon. In the present study, using Laplace's law, we attempt to elucidate the mechanical properties of venules and their valves. We speculate that the remarkably thin venular walls (and especially those of the smaller vessels which have the thinnest walls), are capable of considerable, rapid distension when subjected to increased hemostatic pressure. The increase in diameter of venules in response to the increased blood pressure renders their valve leaflets incompetent, so that the valves themselves cannot close the vessel lumen. In addition, the thin bicuspid leaflets may also be forced open retrogradely by the increased blood pressure.
通过静脉系统进行强制性逆行灌注，动脉血液可以通过静脉-毛细血管网络为休息时的外周组织提供足够的氧气，这是通过远端静脉动脉化（DVA）恢复血流的手术基础。为了使此类手术成功，需要破坏静脉中的瓣膜小叶，这在较大的血管中很容易实现。然而，直径小于 100μm 的最小静脉（小静脉）也具有瓣膜，广泛分布于所有组织中，并且过于精细，无法进行任何有效的手术干预。因此，目前可用的技术无法破坏或解剖小静脉瓣膜。尽管如此，临床观察表明，DVA 手术后逆行外周血流迅速建立。对于这种现象，目前还没有合理的解释。在本研究中，我们使用拉普拉斯定律尝试阐明小静脉及其瓣膜的力学特性。我们推测，当受到更高的止血压力时，非常薄的小静脉壁（尤其是那些壁最薄的较小血管）能够迅速扩张。小静脉对血压升高的反应导致其瓣膜小叶功能不全，从而使瓣膜本身无法关闭血管腔。此外，增加的血压也可能使薄的二尖瓣叶逆行性被迫打开。
