Determining In-Stent Stenosis of Carotid Arteries by Duplex Ultrasound Criteria

Abstract

Purpose: To develop customized duplex ultrasound criteria for assessment of in-stent restenosis in the carotid arteries. Methods: A retrospective review was conducted of 605 patients who underwent carotid artery stenting (CAS) from July 1996 to August 2004 at a single institution. Data on the stented carotid artery were accumulated from patients who had carotid angiography and duplex ultrasound (US) within 30 days of each other. Preliminary review found 118 pairs of ultrasound scans and angiograms in stented carotid arteries. Peak systolic velocity (PSV), end-diastolic velocity (EDV), and internal carotid artery to common carotid artery ratio (ICA/CCA) were examined. Angiographic stenosis was graded by NASCET criteria and compared to velocity parameters at clinically relevant levels of stenosis. The Student t test was used to compare similarly obtained data from 41 nonstented carotid arteries. Results: PSV, ICA/CCA ratio, and EDV increased to a greater degree in stented arteries with stenosis. In 50% to 69% stenotic arteries, mean ICA/CCA ratio was 4.74±0.61 in stented versus 3.68±0.24 in nonstented carotid arteries (p=0.043). In arteries with ≥0% stenosis, there were increases in PSV (475±22 versus 337±26 cm/s, p=0.001), EDV (172±23 versus 122±8 cm/s, p = 0.043), and the ICA/CCA ratio (8.18±2.19 versus 5.11 ±0.66, p=0.063) in stented versus nonstented arteries, respectively. To detect ≥70% angiographic stenosis, PSV≥350 cm/s had 100% sensitivity, 96% specificity, 55% positive predictive value (PPV), and 100% negative predictive value (NPV); an ICA/CCA ratio ≥4.75 had 100% sensitivity, 95% specificity, 50% PPV, and 100% NPV. To predict >50% stenosis, combining PSV≥225 cm/s and ICA/PCA ratio ≥2.5 increased sensitivity (95%), specificity (99%), PPV (95%), NPV (99%), and accuracy (98%). Conclusions: PSV and ICA/CCA increase with stenosis to a greater extent in stented carotid arteries, necessitating revision of existing US criteria to follow CAS patients. To determine ≥70% in-stent stenosis, PSV≥350 cm/s and ICA/CCA ratio ≥4.75 are sensitive criteria. To determine ≥50% stenosis, combining PSV≥225 cm/s and ICA/PCA ratio ≥2.5 is optimal.