Grading Carotid Intrastent Restenosis: A Six-Year Follow-Up Study

Abstract

Conclusion: Duplex ultrasound imaging can accurately predict intrastent restenosis of stented carotid arteries. Summary: The authors sought to establish duplex criteria for intrastent restenosis after carotid artery stenting (CAS). Duplex velocity parameters were compared with angiography. This was a 6-year study with data obtained prospectively. After CAS, patients underwent angiography for suspected intrastent restenosis. Stenosis was calculated according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method. Angiographic stenosis was then compared with peak systolic velocity (PSV), end diastolic velocity (EDV), and the ratio between the peak systolic velocity of the internal carotid artery and common carotid artery (ICA/CCA). The initial duplex study was done ≤48 hours after angioplasty and served as a baseline result. Follow-up duplex examinations were performed at 30 days, 3,6, 9, and 12 months, and then yearly. If the PSV increased greater than three times the baseline value, or if a PSV >200 cm/s was detected in the stented carotid artery, the patients underwent angiography. There were 814 carotid stent procedures performed. There were 6427 ultrasound examinations and 1123 angiographic studies performed in follow-up. Angiographic intrastent restenosis >70% was detected in 22 and intrastent restenosis >50% in 73. On the basis of comparisons of duplex values and angiograms, velocity criteria for grading carotid intrastent restenosis were <30% stenosis, PSV ≤104 cm/s; 30% to 50% stenosis, PSV 105 to 174 cm/s; 50% to 70% stenosis, PSV ≥175 to 299 cm/s; ≥70% stenosis, PSV ≥300 cm/s, EDV ≥140 cm/s, and an ICA/CCA ratio ≥3.8. Comment: This is arguably, to date, the best article in the literature correlating angiographic findings with duplex findings in patients with intrastent carotid stenosis. It certainly has the largest numbers. It is interesting that the criteria for very-high-grade stenosis (>70%) differ very little from those reasonably well accepted for native artery stenosis. More moderate lesions in stented carotid arteries, however, appear to be associated with higher PSVs than would be anticipated from comparisons of angiograms and native internal carotid artery stenoses. One relative weakness of the current study, and all studies on this subject, is the small number of patients with >70% angiographic restenosis, 11.7% of a total of 814 patients.