Heyligers Jan M M, Verhagen Hence J M, Rotmans Joris I, Weeterings Cees, de Groot Philip G, Moll Frans L, Lisman Ton
Department of Vascular Surgery, University Medical Center, Utrecht, The Netherlands.
J Vasc Surg. 2006 Mar;43(3):587-91. doi: 10.1016/j.jvs.2005.10.038.
The patency of small-diameter expanded polytetrafluoroethylene (ePTFE) grafts for vascular reconstruction is impaired by acute thrombotic occlusion. Prosthetic materials are thrombogenic and cause platelet adhesion and activation of the coagulation cascade. Heparin is a potent anticoagulant drug widely used to prevent and treat thrombosis. A new ePTFE graft with long-term bonding of heparin is now commercially available in several European countries, but a basic analysis of its mechanism of action in humans has never been performed. This study was performed to evaluate the thrombogenicity of heparin-bonded ePTFE grafts compared with standard ePTFE in a newly developed human ex vivo model.
Nonanticoagulated blood was drawn from antecubital veins of 10 healthy donors with a 19-gauge needle. The proximal end of a 60-cm ePTFE vascular graft with a diameter of 3 mm was connected to the needle while the distal end was connected to a syringe, which was placed in a syringe pump. Every volunteer served as his or her own control by using a heparin-bonded ePTFE graft on one arm and a standard ePTFE graft on the other arm. The perfusions were performed over 6 minutes with a flow rate of 20 mL/min, corresponding to a shear rate of 74/s. Serial samples were taken at the distal end of the graft for determination of prothrombin fragment 1 + 2, fibrinopeptide A, and P-selectin expression on perfused platelets. Fibrin deposition and platelet deposition were studied by using scanning electronic microscopy.
Fibrinopeptide A production over time was significantly reduced on the heparin-bonded ePTFE grafts compared with standard ePTFE grafts (P < .05). There was no increase in the production of prothrombin fragment 1 + 2 or P selectin over time on either type of graft. Scanning electronic microscopy scanning showed platelet deposition and fibrin formation on standard ePTFE grafts, whereas no platelets or fibrin were observed on heparin-bonded ePTFE grafts.
Heparin immobilization substantially reduces the thrombogenicity of small-diameter ePTFE in a newly developed human ex vivo model. In this study, we provide evidence that the mechanism of action of the heparin bonding is due not only to anticoagulant but also to antiplatelet effects. Heparin bonding may be an important improvement of ePTFE, resulting in better patency rates for vascular reconstructions.
小口径膨体聚四氟乙烯（ePTFE）移植物用于血管重建时，其通畅性会因急性血栓闭塞而受损。人工合成材料具有血栓形成性，会导致血小板黏附并激活凝血级联反应。肝素是一种广泛用于预防和治疗血栓形成的强效抗凝药物。一种新型的肝素长期结合的ePTFE移植物目前在几个欧洲国家已上市，但尚未对其在人体中的作用机制进行基础分析。本研究旨在通过一种新开发的人体体外模型，评估肝素结合的ePTFE移植物与标准ePTFE相比的血栓形成性。
用19号针头从10名健康供者的肘前静脉抽取未抗凝血液。将一根直径3mm、长60cm的ePTFE血管移植物的近端连接到针头上，而远端连接到一个置于注射泵中的注射器上。每位志愿者均以一只手臂使用肝素结合的ePTFE移植物，另一只手臂使用标准ePTFE移植物，以此作为自身对照。以20mL/min的流速进行6分钟的灌注，相应的剪切速率为74/s。在移植物远端采集系列样本，用于测定凝血酶原片段1 + 2、纤维蛋白肽A以及灌注血小板上P选择素的表达。通过扫描电子显微镜研究纤维蛋白沉积和血小板沉积情况。
与标准ePTFE移植物相比，肝素结合的ePTFE移植物上纤维蛋白肽A随时间的产生量显著降低（P < 0.05）。两种类型的移植物上，凝血酶原片段1 + 2或P选择素的产生量均未随时间增加。扫描电子显微镜扫描显示标准ePTFE移植物上有血小板沉积和纤维蛋白形成，而肝素结合的ePTFE移植物上未观察到血小板或纤维蛋白。
在新开发的人体体外模型中，肝素固定化可显著降低小口径ePTFE的血栓形成性。在本研究中，我们提供证据表明肝素结合的作用机制不仅归因于抗凝作用，还归因于抗血小板作用。肝素结合可能是ePTFE的一项重要改进，可使血管重建的通畅率更高。
