Ultrasound Criteria for Severe In-Stent Restenosis Following Carotid Artery Stenting

Purpose: In-stent restenosis (ISR) is a known complication following carotid artery stenting (CAS). However, ultrasound criteria determining ISR are not well established. We evaluated alternative ultrasound velocity criteria for >70% ISR in our institution.
Methods: Clinical records of 256 patients undergoing 282 consecutive CAS procedures over a 42-month period were reviewed. Follow-up ultrasounds were available for analysis in 237 patients. Selective angiograms and repeat interventions were performed for >70% ISR. Ultrasound criteria including peak systolic velocity (PSV), end diastolic velocity (EDV), and internal carotid to common carotid artery ratio (ICA/CCA) were examined.
Results: Eighteen carotid angiograms were performed and 15 angiograms confirmed >70% ISR on 10 patients including prior CEA in five patients and neck irradiation in two. PSV at 200cm/s, 250cm/s, 300cm/s were evaluated and EDV at 70cm/s, 80cm/s, 90cm/s, and 100cm/s were analyzed. Additionally, ICA/CCA at 3, 4, and 5 were assessed. For 70% or greater angiographic ISR, PSV > 300cm/s correlated to 93% sensitivity, 67% specificity, 93% positive predictive value (PPV), and 67% negative predictive value (NPV); EDV >80cm/s correlated to 93% sensitivity, 100% specificity, 100% PPV, and 75% NPV; and ICA/CCA >4 had 100% sensitivity, 67% specificity, 94% PPV, and 100% NPV. Significant color flow disturbance was detected in one patient who did not meet aforementioned criteria.
Conclusion: Our study demonstrated that PSV>300cm/s, EDV>80cm/s, and ICA/CCA>4 correlated well with >70% ISR. These velocity criteria combined with color flow pattern can reliably predict severe ISR. However, further study is warranted to establish standard post-CAS ultrasound surveillance criteria.