Stent deformation: an experimental study of coronary ostial stenting

Abstract

To investigate stent deformation by torsional stress after implantation at the ostium of a model coronary artery. Little is known about coronary stent deformation, especially the association between stent design and deformation at the coronary ostium. Recent reports have suggested that mechanical factors are important for stent restenosis. A coronary ostium model was constructed and three different stents (Express(2), Cypher, and Tsunami, n=5 each) were implanted at the aorto-ostial junction. Differences of stent deformation were assessed after exposure to torsional stress. Intravascular ultrasound was used to measure the luminal area along each stent. Then the extent and pattern of plastic deformation were compared between the three stent types. The Express(2) stents and Cypher stents both showed significant deformation (P<.0001 and P=.045, respectively) adjacent to the ostium, whereas only a minimal decrease of luminal area was observed with the Tsunami stent. In the central and distal parts of each stent, the decrease of luminal area was minimal and no differences were noted among the three types. Sudden fracture of a Cypher stent strut occurred during the experiment. Differences of structural characteristics influence permanent plastic deformation at sites where continuous stress occurs, such as the coronary ostium. A more elastic design may show better resistance to such stress.