Optimal cut-off criteria for duplex ultrasound compared with computed tomography angiography for the diagnosis of restenosis in stented carotid arteries in the international carotid stenting study

Abstract

Introduction: Previous studies that reported duplex-ultrasound cut-off criteria, based on blood velocity parameters, for the degree of stenosis in a stented carotid artery were either retrospective, or the reference test was carried out only when a patient was suspected of having restenosis at duplex ultrasound, which is likely to have resulted in verification bias. We performed a prospective study of diagnostic accuracy to find new blood velocity cut-offs in duplex ultrasound for in-stent restenosis.

Patients and methods: Stented patients within the international carotid stenting study were eligible. Patients had a carotid computed tomography angiography in addition to routine duplex ultrasound performed at a yearly follow-up. Duplex-ultrasound bloodflow velocity parameters were compared to the degree of stenosis on computed tomography angiography. The results were analysed using receiver-operating-characteristic curves.

Results: We included 103 patients in this study. On computed tomography angiography, 30 (29.1%) patients had a 30%-49% in-stent restenosis, 21 (20.4%) patients had 50%-69% in-stent restenosis and 5 (4.9%) patients a ≥70% in-stent restenosis. The cut-off value ≥50% stenosis was a peak systolic velocity of 125 cm/s (sensitivity: 63% (95% CI: 41-79), specificity: 83% (95% CI: 72-90)).

Discussion: This study provides a level 2b evidence for new cut-off values for in-stent restenosis. Unfortunately, we could not say anything about severe stenosis because of the low number of severe stenosis after one year.

Conclusions: The 125 cm/s cut-off value on duplex ultrasound is lower than found in previous studies and equal to unstented arteries. Duplex-ultrasound measurements made in stented carotid arteries should not be corrected for the presence of a stent when determining the degree of stenosis.

Keywords: Stroke; computed tomography angiography; duplex ultrasound; restenosis; stenting.

Figure 1.

Flow chart. ICSS: international carotid stenting study; CTA: computed tomography angiography; DUS: duplex ultrasound; PSV: peak systolic velocity.

Figure 2.

Scatter plot of the degree of stenosis found on CTA (x-axis) correlated with the PSV in the ICA (a) and the PSV ICA/CCA ratio (b) (y-axis). ICA: internal carotid artery; CCA: common carotid artery; PSV: peak systolic velocity; CTA: computed tomography angiography.

Figure 3.

ROC curves for the cut-off values for PSV in, respectively, (a) ≥30% stenosis (AUC 0.78; p-value ˂0.001; 95% CI 0.69–0.87); (b) ≥50% stenosis (AUC 0.73; p-value ˂0.001; 95% CI 0.61–0.85); and for the ICA/CCA ratio in (c) ≥30% stenosis (AUC 0.73; p-value ˂0.001; 0.63–0.83) and (d) ≥50 stenosis (AUC 0.73; p-value 0.001; 95% CI 0.61–0.86).