Background and purpose During carotid artery stenting (CAS) with the use of closed cell design stents for unstable plaques, tissue prolapse between stent struts was evaluated by optical coherence tomography (OCT).

Methods 14 carotid stenosis lesions diagnosed as unstable plaques by MRI were evaluated by OCT imaging during CAS using closed cell stents. Cross sectional OCT images within the stented segment were evaluated at 1 mm intervals. The slice rate for the presence of tissue prolapse between the struts was calculated.

Results No intra-procedural complications occurred. After single stent placement, plaque prolapse was observed in all cases. Slices with any and >500 µm tissue prolapse were seen in 30% and 7.8% of cases, respectively. In 5 of 7 lesions with tissue prolapse >500 µm, additional stents were overlapped. In cases with overlapping stents, slices with any tissue prolapse were significantly decreased from 26% to 16% (p=0.008); in particular, the occurrence of tissue prolapse >500 µm was significantly decreased from 15% to 2.3% (p<0.001). In one case of >500 µm tissue prolapse without an overlapping stent, delayed embolization due to an in-stent thrombus occurred 9 months after the procedure.

Conclusions OCT during CAS using closed cell stent for unstable plaques frequently revealed tissue prolapse between struts. Placement of overlapping stents significantly reduced tissue prolapse, particularly tissue prolapse >500 µm. However, closed cell stents used for unstable plaques may not solve the problem of tissue prolapse.