STENT LONGITUDINAL FLEXIBILITY BEFORE AND AFTER EXPANSION: A COMPARISON OF 13 COIL, HYBRID OR SLOTTED TUBE DESIGNS
J.A. Ormiston*, M.W.I. Webster, P.N. Ruygrok, I. Minchington, J.T. Stewart, B.J. O'Shaughnessy.
Mercy and Green Lane Hospitals, Auckland, and Industrial Research Ltd, Wellington, New Zealand.
Background: An ideal stent should be highly flexible when unexpanded to negotiate tortuous anatomy. When expanded it must be sufficiently flexible to conform to vessel contour minimising stent/vessel junction distortion, but still have adequate radial strength and vessel coverage. In vitro testing of unexpanded and expanded stent flexibility/stiffness may aid the interventionalist in clinical stent selection.
Methods: A 3 point bend test was performed using an Instron to measure the force needed to bend stents 1.5mm. Stent stiffness (slope of the force/displacement plot), was determined for 13 designs in the unexpanded state (internal diameter 1.64mm) and after expansion with a 3.5mm balloon.
Results: Stents are depicted according to stiffness in the unexpanded state.
Conclusions: All stents became stiffer when expanded. There is a wide range of flexibility with coil stents (Wiktor-I, Crossflex) being more flexible than the hybrid designs (AVE GFX, BARD XT) which are in turn more flexible than the "slotted tube" type stents.
