Abstract 2419: Ultrasound Velocity Criteria for Carotid In-Stent Restenosis
Background: Carotid artery stenting is an alternative to surgery in the treatment of carotid stenosis, and as a result, in-stent restenosis (ISR) will be encountered more frequently. Duplex ultrasound, using velocity information, is the primary means to follow carotid stents. Deployment of a stent may alter velocity measurements by causing changes in the mechanical properties of the vessel. We present our single center experience on ultrasound velocity criteria in carotid stent ISR.
Method: Two hundred patients underwent carotid stenting at Ochsner Clinic with follow-up duplex studies in our ICAVL accredited laboratory. The velocity criteria for native carotid stenosis >70% (peak systolic velocity [PSV] ≥240 cm/s or internal carotid to common carotid PSV ratio ≥ 2.0) was used to screen for ISR. Patients with duplex ISR > 70% underwent quantitative angiography. We also analyzed patients with native (without stent) carotid stenosis who had an angiographic correlation.
Result: Ten patients had ISR >70% by duplex with an overall restenosis rate of 5%. Compared to patients with native (without stent) carotid artery > 70% narrowing on US, the ISR patients had a lower mean angiographic stenosis (76% ±9%) than the patients with native carotid stenosis (84% ± 9%; P< .01) despite having a higher PSV (416 ± 140 cm/s vs 353 ± 74 cm/s; P< .01).
Conclusion: Our data suggest that the presence of a metal stent alters the compliance of the carotid artery, falsely elevating PSVs. This suggests that the current criteria for native (without stent) carotid arteries may overestimate the incidence of ISR and as a result could increase the frequency of unnecessary carotid angiograms.