[Biophysical study of coronary stents: which factors influence the dilatation and recoil behavior?]

In Europe more than fifty stents are currently available for the therapy of coronary artery disease. Nonetheless it is unknown whether material and design influence the stent's behavior. We have studied the recoil and dilatation behavior of five currently available stainless steel (316L) stents compared to stent prototypes made of pure titanium. Furthermore we have investigated how the behavior is influenced by the process of crimping. The aim of this work was to determine material and design characteristics, which influence the recoil and dilatation behavior. The 316L stents showed a homogeneous behavior (plateau pressure min. 1.15 +/- 0.01 atm, max. 0.26 +/- 0.03 atm, recoil min. 0.15 +/- 0.03%, max. 0.26 +/- 0.03%). The titanium stent showed a linear response to the balloon expansion. This was seen in a significantly lower plateau pressure (0.43 +/- 0.15 atm, p < 0.001). Despite the material characteristics of titanium, there were no significant differences in the recoil behavior (0.28 +/- 0.02%). Crimping leads to stent alterations which result in a significantly higher plateau pressure (1.9 +/- 0.07 atm vs. 2.7 +/- 0.58 atm, p < 0.001) and a reduced end-diameter (3.6 +/- 0.02 mm vs. 3.54 +/- 0.05 mm, p < 0.005). The presented data show that the dilatation behavior is relying on the stent material while the recoil is strongly influenced by the stent design.