Types of anastomosis creation in AVF
Despite the generally low rate of complications of native AVF, early failure within 1 month has been observed in some patients.
Early failure, defined as non-function of the AVF, is mostly caused by early thrombosis secondary to errors in the surgical technique. Analysis of the surgical techniques for the creation of an arteriovenous anastomosis has identified a number of potential errors which may contribute to such early failure.
Haemodynamics of the arteriovenous fistula
Blood-flow rates in a well-functioning AVF can exceed 1000 ml/min or more—a dramatic increase when compared with a blood flow rate of 20-30 ml/min in a normal peripheral artery and the immediate post-operative flow rate of 200-300 ml/min after the opening of the fistula. This is accompanied by a decrease in peripheral resistance.
In the past, venous dilatation has been the focus of attention, but today we understand that the entire vascular bed (arterial and venous behaviour) must undergo dramatic remodelling in order to accommodate the extremely high blood-flow rates.
The arteriovenous anastomosis
The first step is to select a suitable “healthy” artery and vein. This can be done by clinical and ultrasonographic investigation. Most procedures creating a primary vascular access can be carried out under local anaesthesia.
There are three basic types of arteriovenous anastomosis:
Side-to-side anastomosis lets blood flow in both directions.
With vessels in good condition and functioning venous valves, it is less likely to develop complications; however, it has proved to have more disadvantages and complications than other techniques.
End-to-end anastomosis also lets blood flow in both directions. It was fashionable in the past but has several disadvantages: (1) the diameters of the artery and the vein differ, and this has to be overcome by inserting a rhombus-like vein patch into the suture; (2) the suture itself is performed in three independent sections without any connection between the closing knots.
This procedure is dangerous in diabetic and elderly patients who constitute the majority of patients currently seen.
End-to-side anastomosis is the preferred technique today. With this technique the vein is isolated and has to be approximated to the artery across a certain distance. The angle between artery and vein at the site of the anastomosis differs from case to case. Each angle requires an individual length of arteriotomy and venotomy and requires close attention. The correct angle allows for preserved patency rates and reduces future complications.
How can VasQ device help with an end-to-side anastomosis?
The surgeon must be aware of the anatomical, physiological, haemodynamic, and mechanical principles underlying the procedure, and this must be combined with manual skill, experience, and creativity.
The VasQ device was designed to regulate anastomosis geometry and resulting flow patterns. It provides external support and thereby:
(1) regulates flow by constraining and shaping optimal geometrical parameters of the fistula;
(2) reinforces and shields the vulnerable perianastomotic vein against high pressure, wall tension, and flow levels. Read more >>>>
- Arteriovenous Access Surgery by Hans Schultz