Dilatation of the Ileo-Femoral Artery Following the Opening of an Experimental Arterio-Venous Fistula in the Dog

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Abstract
Vascular calibre was measured along the ileo-femoral artery in dogs proximal to a fistula established between the femoral artery and vein. Two methods were employed for arterial diameter recording: 1) ultrasonic technique, and 2) radiographic studies. In the series of animals examined by ultrasonic technique a maximum increase of 19% was found in the diameter of the external iliac artery immediately after opening the fistula. Radiographic studies were started 70 min after opening the fistula and continued in 14 experiments at various stages up to 9 months after establishment of the fistula. The initial dilatation of the external iliac artery corresponded to an increase of 18 ± 3.4% (mean ± S.E.M.) in the radiographic series and 12.3 ± 5.5 % measured by the ultrasound technique. The difference is not significant. The radiographic series demonstrated an additional dilatation of the femoral artery proximal to the fistula, increasing with time. Radiographic and ultrasound measurements provide comparable results. It is concluded that there is a smooth transition from an immediate dilatation response to a chronic enlargement of the artery proximal to an arterio-venous fistula. We propose that the sudden increase in velocity and blood flow following a local fall in peripheral resistance is the cause of the immediate dilatation of the ileo-femoral artery. The additional, later dilatation of the femoral artery proximal to the fistula may be related to vortices in the fistula and its vicinity and to vibrations of the arterial wall.