Haemodynamics in axillobifemoral bypass grafts

This thesis is based on four publications on the subject of graft configuration and haemodynamics in axillobifemoral bypass grafts: 1. A clinical evaluation of 17 patients with axillobifemoral bypass graft operations, performed for various indications. Two important observations were made: an asymmetrical blood flow distribution between the two distal branches, in favour of the ipsilateral branch, and turbulent flow at the site of the bifurcation, as observed with duplex scanning. These observations, described in chapter 2, led to the development of a new design for an axillobifemoral bypass graft. 2. The second publication is a report of the results of an in-vitro study, performed to analyse the haemodynamical properties of three currently used axillobifemoral bypass graft configurations (with contralateral branches at angles of 30°,90° and 150° ) and the newly designed axillobifemoral bypass graft. The pressure drops across the four different axillobifemoral bypass bifurcation configurations under sinusoidal flow of a Newtonian fluid were analysed at four different flow rates at three different systemic mean pressures. This invitro experiment is described in chapter 3. 3. The third publication reports on the haemodynamical in-vivo properties of two different axillobifemoral bypass graft configurations (one with a contralateral branch at an angle of 90° and one with a symmetrical bifurcation and flowsplitter). This in-vivo study was conducted, because the in-vitro study was performed with a sinusoidal pulsatile flow of a Newtonian fluid, which has a different impact on flow profi1es and flow disturbances than the in-vivo physiological pulsatile flow of a non-Newtonian fluid, namely blood. All pressure losses across the bifurcation, ipsilateral and contralateral, were measured at different flow rates. The results are discussed in chapter 4. 4. In order to evaluate the clinical relevance of these findings, an international multicenter prospective randomized trial was conducted. The patency rates and clinical behaviour of the two different axillobifemoral bypass grafts, differing only in configuration of the bifurcation (one with a contralateral branch at an angle of 90° and one with a flowsplitter), were analysed in this trial. In 19 centers in Germany, Belgium, France and the Netherlands 117 patients were randomized, 59 receiving a prosthesis with a flowsplitter and 58 a prosthesis with a 90° bifurcation. Analysis of the results after 3 years with a mean follow up of 12 months is discussed in chapter 5.

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