Conformability of balloon-expandable stents to the carotid siphon: an in vitro study

Abstract

Background and purpose: Endovascular placement of coronary balloon-expandable stents in patients with recurrent cerebral ischemia has emerged as a treatment option for intracranial arterial occlusive disease. We have developed an in vitro model matching the tortuous curve of the carotid siphon that allows the assessment of apposition of stents to a curved vessel wall.

Methods: Six types of balloon-expandable coronary stents were implanted in a silicone model of the carotid siphon. Digital radiographs and 3D rotational angiograms were obtained. Stent morphology was evaluated and the degree of apposition between stent and wall of the model was measured on a digital workstation.

Results: All 6 stents showed lack of apposition between stent and the wall at the convexity of the anterior segment of the carotid siphon and the wall at the concavity at both extremities of the stent. In and around the curve, the modules of the stents did not expand completely to their nominal diameter and were distorted to an oval shape.

Conclusion: The tested coronary balloon-expandable stents did not completely conform to the vessel wall of the model of the carotid siphon and further development is needed to approach the goal of an "ideal intracranial stent."

Fig 1.

Measurement of apposition of the stent to the carotid siphon shaded in gray. A, Area between stent and the wall at the convexity of the anterior segment of the siphon. B, Area within the stent. C, Area between stent and wall at the concavity at both extremities of the stent.

Fig 2.

Digital images (1) and 3D rotational images (volume rendering) (2) of the 6 balloon-expandable stents after implantation in the silicone model of the carotid siphon (A) Cordis Bx Sonic, (B) Medtronic RX Driver, (C) Biotronik Lekton Motion, (D) Guidant Multi-Link Vision, (E) Boston Scientific TAXUS Express2, and (F) Terumo Tsunami Gold. Note the limited conformability especially to the outer curve.

Fig 3.

A, Measurements of the area within the stent (first bar). The summation of the area between stent and the wall at the convexity of the anterior segment of the siphon and the wall at the concavity at both extremeties of the stent (second bar) for all tested stents. B, Apposition ratio: area between stent and vessel wall in relationship to the area within the stent.