Based on the experimental experiences in more than 180 implantations of different materials as venous substitutes segments of the inferior vena cava have been replaced in 34 dogs by Polyurethane (low microporosity) and modified e-PTFE prostheses (increased microporosity of 60 microns and 90 microns fibril length). The 12 months patency rate didn't differ between both tested optimized materials and ranged from 43 to 50%. After a follow-up of 12 months the grafts were taken out and analysed by light, immunofluorescence microscopy, scanning and transmission electron microscopy. In addition a new technique of microcorrosion casts was used for SEM-analyses. As a result a transmural microvessel system in the microporous meshwork of the prostheses with multiple orifices at the inner surface of the grafts could be demonstrated. Complete endothelialization was only observed in e-PTFE prostheses of high microporosity (greater than 60 microns fiber length). There is strong evidence that a full tissue incorporation of microporous artificial grafts mainly depends on a sufficient primary intramural deposit of blood components (fibrin, platelets, leucocytes), which initiates cell invasion from the surrounding tissue, accompanied by a highly developed microvessel network. A multifocal endothelialization takes place from the numerous microvascular orifices on the inner surface of the prostheses. Other sources such as pannus invasion or adhesion of multipotent cells from the blood stream play probably a very limited role.
In reconstructive vascular surgery several intraoperative investigations are in use to check-up and secure full blood flow restoration (angiography, ultra-sound, electro-magnetic flowmeter etc.). In the last years endoscopical lumen control, introduced 1969 in clinical praxis, could be remarkably simplified and improved. For vascular endoscopy three technical prerequisites are necessary: a) temporary interruption of blood flow using clamps or balloon catheters, b) replacement of the blood by a transparent medium via pressure controlled saline perfusion, c) availability of suitable special endoscopes. The main application of vascular endoscopy includes: a) semi-closed thromboendarterectomy (aorto-iliac or femoropopliteal), b) arterial embolectomy, c) lumen control of inserted grafts including the anastomosis and the distal run-off vessels, d) venous thrombectomy. The availability of small-calibre endoscopes (external diameter: 1.7-2.7 mm) enables the extension of lumen control to small vessel areas such as the tibial and coronary arteries. Compared with angiography vascular endoscopy offers several convincing advantages such as a more reliable three dimensional lumen control, easy performance, saving time and the avoidance of any additional X-ray exposure. Technical faults or overlooked concomitant vascular lesions can be diagnosed and corrected immediately.
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