The residual risk of cerebral embolism after carotid stenting: the complex interplay between stent coverage and aortic arch atherosclerosis.

ABSTRACT

AIM: This study investigated the fate of the stent inner surface in carotid artery stenting (CAS). In addition, the occurrence of late cerebral micro-embolism after CAS has been studied in order to identify predictors and correlate it with a possible neo-intimal layer. METHODS: A series of patients were evaluated before CAS through aortic arch trans-oesophageal echocardiography. Six months after CAS, the stent coverage by neo-intima and the possible presence of uncovered plaques were determined by high-resolution duplex scanning (5-17-Hz probe and 3D reconstruction). Possible micro-embolic signals (MESs) were evaluated through transcranial duplex scanning (30-min analysis of ipsilateral middle cerebral artery with a 1-4-Hz probe) and correlated with patients' characteristics, intimal media thickness (IMT) (>0.9mm vs. <0.9mm) and uncovered proximal plaques, type of stent (closed vs. open cells) and aortic arch complicated plaques (>4mm). Fisher's and Wilcoxon tests were used to evaluate differences across groups for categorical and continuous variables, respectively. RESULTS: In the 68 CASs examined (40 closed cells and 28 open cells), the stent was completely covered by neo-intima in 52 cases (76.4%). Complete coverage was significantly correlated with IMT<0.9mm and the absence of a proximal plaque uncovered by the stent (100% vs. 0%, p<0.001). Hypertension was an independent predictor of complete intimal coverage (p=0.002), while the stent type did not influence this process. The MESs were significantly more frequent in patients with complicated aortic arch plaques (62.5% vs. 23.8%, p<0.012), independently from all other factors. CONCLUSIONS: The extent of the stent neo-intimal formation is independent of stent type, but it is correlated with proximal plaque coverage. Six months after CAS, MESs are still possible and are not prevented by complete neo-intimal stent coverage. Complicated aortic arch atherosclerosis is an independent predictor of late MES, thus underlying its importance in cerebral ischaemia onset.