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 de sign influence the stent's behavior. We have studied the recoil and dilatat ion behavior of five currently available stainless steel (316L) stents comp ared to stent prototypes made of pure titanium. Furthermore we have investi gated how the behavior is influenced by the process of crimping. The aim of this work was to determine material and design characteristics, which infl uence 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 ballon expansion. Th is 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 sign ificant differences in the recoil behavior (0.28+/-0.02%). Crimping leads t o 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 enddiameter ( 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 sten t material while the recoil is strongly influenced by the stent design.