Stent longitudinal flexibility: A comparison of 13 stent designs before and after balloon expansion

Longitudinal flexibility is an important property of coronary stents, facil itating delivery and allowing the expanded stent to conform to vessel conto ur. Subjective descriptions of flexibility abound, but there are few indepe ndent quantitative data to aid stent selection. A three-point bend test was employed to measure stiffness, the reciprocal of flexibility, for 13 stent designs in the unexpanded (bare) state, then after expansion with a 3.5-mm balloon. For eight of the designs, stiffness of the proprietary stent/ball oon delivery system was also measured. In the unexpanded state, there was a wide spread of stiffness, which ranged from 0.5 +/- 0.2 to 91.5 +/- 10.0 g force/mm, depending on design. Stiffness was least for the coil (Wiktor an d Crossflex) and hybrid (AVE GFX and Bard XT) designs. The MultiLink was th e most flexible and the Crown the stiffest of the slotted tube designs. All stents became stiffer upon expansion. For most manufacturer-mounted stents , the delivery balloon was the main determinant of stent/balloon delivery s ystem stiffness. Manufacturer-mounted stent profile ranged from 1.15 +/- 0. 11 mm for the Jostent to 1.53 +/- 0.05 mm for the MultiLink system. Indepen dent quantitative assessment of characteristics such as flexibility and pro file should aid rational comparison of stent designs. (C) 2000 Wiley-Liss, Inc.