2007 Abstracts: Duplex Scan Surveillance After Carotid Stent-Angioplasty - A Rational Definition of Stent Stenosis.

Background: Criteria for interpreting duplex-detected stenosis after carotid artery stenting (CAS) are in evolution. An algorithm for surveillance after carotid endarterectomy was applied to patients after CAS to determine the frequency and progression to high-grade stenosis and ipsilateral neruologic events.
Methods: In 111 patients who underwent 114 CAS procedures for symptomatic (n=62) or asymptomatic (n=52) atherosclerotic carotid bifurcation stenosis, duplex surveillance was performed within 30 days and every 6 months after the procedure. High-grade stenosis involving the stent or ICA (PSV>300 cm/s, diastolic velocity>125 cm/s, ICA stent/proximal CCA ratio >4) prompted the recommendation for reintervention. CAS stenosis ≥50% diameter reduction (DR) was defined a PSV>150 cm/s with ICA/CCA ratio>2.
Results: No perioperative strokes, deaths, or stent occlusions occurred. The results of duplex surveillance of the 114 CAS sites during a mean follow-up interval of 24 months were:

NA, not applicable
^* mean time to progression of CAS stenosis 14±10 mo.
⁺ mean time to regression of CAS stenosis 9±7 mo.
During follow-up, three patients developed non-disabling reversible neurologic events (30, 45, and 120 days) and duplex testing detected no CAS stenosis in two and >50% DR in one patient. The yield of duplex surveillance for high-grade CAS stenosis was 5% (6 of 114 CAS sites) - no stent occluded. Angiography confirmed >75% DR CAS stenosis in all 6 patients; resulting in balloon angioplasty (n=3), stent angioplasty (n=2), and in one patient stent removal with endarterectomy. After 30-days, no patient with >50% CAS stenosis on initial testing or who demonstrated stenosis progression to >50% DR developed ipsilateral neurologic symptoms. No CAS or stroke-related deaths were observed.
Conclusion: Routine duplex surveillance after CAS yielded a 5% rate of failure due to high-grade in-stent stenosis. Serial duplex testing identified both progression and regression of in-stent stenosis with the majority (70%) of CAS sites demonstrating velocity spectra of <50% DR. A policy of surveillance and re-intervention for high-grade stenosis was associated with CAS patency and absence of disabling stroke for asymptomatic high-grade stenosis.