Estimating the "Pull" on a Pullthrough Wire: A Pilot Study

Pullthrough/body floss wires are used to track endovascular devices across tortuous aorto-iliac anatomy encountered during endovascular repair of abdominal or thoracic aortic aneurysms. The tension imparted on such wires is arbitrary and has never been quantified. This pilot study attempted to quantify the tension used to stiffen the floppy hydrophilic wires typically used in such a scenario.

Two linked experiments were undertaken, the first by tasking 13 blinded vascular surgeons (eight male, five female; mean age 36 ± 11 years, including nine trainees) with pulling a long floppy hydrophilic wire (Radifocus Guidewire M Stiff, Terumo UK, Bagshot, Surrey, UK) attached at the other end to a horizontally configured industrial scale (HDN-N Hanging Scale, Kern & Sohn GmbH, Balingen, Germany), to simulate what they individually felt was an "appropriate" tension; the second by using the derived average tensioning force to set up a pullthrough wire within a rigid life like aorto-iliac model to assess whether a test device (16F Sentrant Introducer Sheath, Medtronic Limited, Watford, UK) could be delivered over such a tensioned wire in both brachiofemoral and femorofemoral configurations.

The mean tension exerted by the group on the wire was 38.3 ± 14.8 N (equivalent to 3.9 kgf). Pullthrough wire tensioning was undertaken by fixing one end and applying a 3.9 kg weight at the other. The test device was successfully deployed into the infrarenal aortic position and also across the aortic bifurcation, via brachiofemoral and femorofemoral pullthrough configurations, respectively.

Successful test device deliveries suggest that a minimum tension equivalent to almost 4 kgf applied to a floppy wire can provide "stiffeningˮ to allow device tracking across tortuous aorto-iliac anatomy. More studies are needed to ascertain whether lower tensions can be applied; these results may help provide a platform for other such studies depending on configuration, aortic geometry, and device or wire/tension characteristics.