Quantifying the Functional Stiffness of Pullthrough Wires Used for Endovascular Aneurysm Repairs Using Comparative Tension Dynamometry

OBJECTIVE: There are only few studies on the stiffness of guidewires used to deliver devices during endovascular procedures, particularly abdominal/thoracic endovascular aneurysm repair. In certain situations, tensioned pullthrough wires are also used, but no studies have examined their effective/functional stiffness. The objective of this study was to assess the radial stiffness characteristics of pullthrough wires compared with standard stiff wires. METHODS: Two types of stiff guidewires (Lunderquist Extra-Stiff and Amplatz Super Stiff; 0.035″ × 260 cm), were compared with a floppy guidewire (Radifocus Stiff M; 0.035″ × 260 cm) in two configurations: standard (non-tensioned) and pullthrough (tensioned). Radial stiffness was defined as the peak deformation force (PDF; newtons [N]) needed to deform the wires on an electromechanical dynamometer; data were logged on proprietary dynamometric software and peak load values assessed per wire. Three experimental runs were performed on three fresh sets of each wire per configuration. PDFs from straight configuration to midwire deformation at 15 mm were translated into Microsoft Excel for statistical analysis in Minitab 19 for Windows. RESULTS: Mean ± SD PDFs were 7.83 ± 0.23 N for the Lunderquist and 9.87 ± 0.92 N for the Amplatz. This was 7.84 ± 0.52 N for the Radifocus wire in standard configuration, which increased to 15.48 ± 0.33 N when the Radifocus wire was in pullthrough configuration. This was significantly higher than both the Lunderquist and Amplatz Super Stiff wires (p < .001, one way analysis of variance). CONCLUSION: This study affirmed that a pullthrough wire becomes functionally more rigid than typical stiff wires used for endovascular procedures, and it is this stiffness that allows device delivery.