Carotid artery dynamics during head movements: a reason for concern with regard to carotid stenting?

PURPOSE

To evaluate carotid artery mobility patterns during head movements following carotid angioplasty/stenting (CAS).

METHODS

In 7 patients (all men; mean age 69 years, range 65-76) who had undergone unilateral CAS, 3D time-of-flight magnetic resonance angiography was performed, visualizing both carotid arteries in 5 different head positions (neutral, turned left and right, and bent forward and backward). Maximum intensity projection reconstructions were obtained to measure angulation at the proximal and distal stent junction. Configuration changes of the stented section of the carotid artery and the unstented contralateral artery were judged. Secondly, transverse sections at the level of the carotid bifurcation and at the skull base were used to calculate torsion shear in the common and internal carotid arteries (CCA, ICA) during left and right head position. Results were expressed as median (range).

RESULTS

In neutral head position, maximal angulation at the distal stent junction was 34.3 degrees (32.3 degrees-55.6 degrees). With the head bent forward, this angulation changed to 47.6 degrees (42.6 degrees-85.2 degrees, p=0.028) and when bent backward to 26.5 degrees (25.0 degrees-48.7 degrees, p=0.027). In all patients, configuration changes of the stented sections were absent. The contralateral unstented side showed diffuse configuration changes without specific angulation at one location. With the head turned left and right, the CCA on the stented side was subjected to 28.6 degrees (13.6 degrees-53.7 degrees) and 24.9 degrees (2.0 degrees-50.6 degrees) of torsion shear, respectively. Torsion of the ICA was subsequently 18.1 degrees (12.7 degrees-40.5 degrees) and 15.2 degrees (2.9 degrees-69.4 degrees).

CONCLUSIONS

Following carotid stenting, sharp ICA angulation that are aggravated by forward bending of the head occur at the distal stent junction. The stented section of the carotid artery shows complete lack of flexibility despite highly flexible features of hte stents ex vivo. Both the CCA and ICA are subjected to considerable torsion shear with the head turned left and right. This shear is not accommodated by the current stent designs.