Utility and accuracy of duplex ultrasonography in evaluating in-stent restenosis after carotid stenting

Role of carotid duplex in the assessment of carotid artery restenosis after endarterectomy or stenting

Introduction

Redo carotid endarterectomy (CEA) and carotid stenting (CAS) are often performed when there is evidence of post-procedural restenosis. The incidence of restenosis after carotid reconstruction is not negligible, ranging from 5 to 33%. The diagnosis of significant internal carotid artery (ICA) restenosis is usually based on duplex ultrasound (US) criteria, mostly on peak-systolic flow velocity (PSV). However, there have been no generally accepted duplex US criteria for carotid restenosis after CAS or CEA.

Methods

In this systematic review, the PubMed/ Medline and Scopus databases were screened to find trials that reported duplex US criteria for significant restenosis after CEA and/or CAS. Only those reports were analyzed in which the restenoses were also assessed by CT/MR or digital subtraction angiography as comparators for duplex US.

Results

Fourteen studies met the predetermined search criteria and were included in this review. In most studies, PSV thresholds for significant in-stent ICA restenosis after CAS were higher than those for significant stenosis in non-procedurally treated (native) ICA. Many fewer studies investigated the US criteria for ICA restenosis after CEA. Despite the heterogeneous data, there is a consensus to use higher flow velocity thresholds for assessment of stenosis in stented ICA than in native ICA; however, there have been insufficient data about the flow velocity criteria for significant restenosis after CEA. Although the flow velocity thresholds for restenosis after CAS and CEA seem to be different, the large studies used the same duplex criteria to define restenosis after the two procedures. Moreover, different studies used different flow velocity thresholds to define ICA restenosis, leading to variable restenosis rates.

Discussion

We conclude that (1) further examinations are warranted to determine appropriate duplex US criteria for restenosis after CAS and CEA, (2) single duplex US parameter cannot be used to reliably determine the degree of ICA restenosis, (3) inappropriate US criteria used in large studies may have led to false restenosis rates, and (4) studies are required to determine if there is a benefit from redo carotid artery procedure, such as redo-CEA or redo-CAS, starting with prospective risk stratification studies using current best practice non-invasive care alone.

Ultrasound Criteria for Assessment of Vertebral Artery Origins

BACKGROUND AND PURPOSE

We sought to validate ultrasound as a reliable means of assessing vessel stenosis of vertebral artery origins.

METHODS

We reviewed 1,135 patient charts with ultrasound of the posterior circulation performed in 2008-2015 in a single hospital. Inclusion criteria for native vessels consisted of ultrasound and digital subtraction angiography (DSA) performed within 3 months. Patients with indwelling stents were analyzed separately from native vessels. Using DSA as the gold standard, we determined sensitivity and specificity of ultrasound in detecting occlusion at vertebral artery origin. All patients with nonoccluded native vertebral artery origins were evaluated for degree of stenosis on DSA, and compared to mean flow velocity (MFV), peak systolic velocity (PSV), and end-diastolic velocity (EDV) on ultrasound.

RESULTS

Among 218 vertebral artery origins in 139 patients evaluated, ultrasound showed sensitivity of 85.7% (95% confidence interval (CI): 69.7-95.2%) for occlusion and specificity of 99.5% (95%CI: 96.9-99.9%). Among 126 arteries without occlusion, <50% stenosis had average MFV (39 ± 19 cm/s), 50-69% stenosis had average MFV (68 ± 35 cm/s), and severe (70-99%) stenosis had average MFV (120 ± 93 cm/s) (P < .001). MFV cutoff value of 44 cm/s corresponded to 77% sensitivity and 70% specificity to detect vertebral artery origin stenosis >50% (C-statistic: .81). PSV value of 97 cm/s corresponded with 72% sensitivity and 70% specificity to detect >50% stenosis (C-statistic: .77). MFV cutoff value of 60 cm/s corresponded with 70% sensitivity and 82% specificity to predict 70-99% stenosis (C-statistic: .83). PSV cutoff value of 110 cm/s corresponded with 80% sensitivity and 72% specificity to predict 70-99% stenosis (C-statistic: .84).

CONCLUSION

Ultrasound has good sensitivity and excellent specificity for detecting vertebral origin occlusion. Flow velocity can be used to screen for severe stenosis of vertebral artery at origin.

In-Stent Restenosis After Carotid Artery Stenting: From Diagnosis to Treatment

Although carotid artery stenting is a safe and effective treatment for preventing ischaemic stroke in significant carotid atherosclerotic disease, it can be complicated by in-stent restenosis (ISR). Factors involved in the ISR process are both mechanical and patient-related, but the most important is the neointimal thickening within stent struts, leading to lumen reduction. Overall incidence of carotid ISR is low and related embolic risk seems to be lower than native disease. Digital subtraction angiography is the gold standard for diagnosis. Nowadays, Doppler ultrasound should be considered the first-line investigation, due to its non-invasiveness and reproducibility. Computed tomography angiography remains useful when Doppler ultrasound is inconclusive. Indication and modality of treatment of ISR are still debated: both surgery (carotid endarterectomy with stent removal in most cases) or interventional procedures such as percutaneous transluminal angioplasty with simple balloon, cutting-balloon, drug-eluting balloon, and stenting, showed safety and efficacy in follow-up. Surgery is currently reserved for selected cases. Carotid ISR is an overall rare complication which can be easily identified at routine follow-up. This paper is a literature review and state-of-the-art assessment of ISR, clinical features, diagnosis, and treatment.

Neurosonology and noninvasive imaging of the carotid arteries

In this chapter, we review imaging of the extracranial carotid arteries and the indications for noninvasive carotid artery evaluation, measuring the degree of arterial stenosis and plaque morphology. We also analyze the types of noninvasive imaging, including carotid duplex ultrasound, transcranial Doppler, magnetic resonance angiography, and computer tomography angiography. We look at each of these modalities, briefly discussing techniques, benefits, limitations, and sources of error. Furthermore, we discuss the apparent accuracy and the need for multimodality imaging. Finally, an imaging algorithm for the evaluation of the extracranial carotid arteries is proposed, which is in routine use at our hospital.

Optimal ultrasound criteria for defining the severity of vertebral artery in-stent restenosis

The aim of the study described here was to establish ultrasound criteria for defining the severity of vertebral artery in-stent restenosis. A total of 197 patients with vertebral artery stents were enrolled in this study. Color Doppler ultrasonography was performed after stenting. Peak systolic velocity and end-diastolic velocity within the stent (PSV(stent), EDV(stent)) and at the intervertebral segments were recorded. The ratio of the PSV at the origin to that at the intervertebral segment was calculated. With digital subtraction angiography as the reference standard, the optimal cutoff values of hemodynamic parameters identifying 50%-69% and 70%-99% restenosis were determined by receiver operating characteristic analysis. The optimal cutoff values of hemodynamic parameters identifying 50%-69% restenosis were PSV(stent) ≥ 170 cm/s, EDV(stent) ≥45 cm/s and PSV ratio ≥2.7, and those for 70%-99% restenosis were PSV(stent) ≥220 cm/s, EDV(stent) ≥55 cm/s and PSV ratio ≥4.2. In conclusion, color Doppler ultrasonography is a reliable method for monitoring patients with avertebral artery stents.

The role of contrast-enhanced ultrasound in imaging carotid arterial diseases

The standard of care for the initial diagnosis of carotid artery bifurcation diseases is carotid duplex ultrasound. Carotid abnormalities or difficult examinations may represent a diagnostic challenge in patients with clinical symptoms as well as in the follow-up after carotid endarterectomy, carotid artery stenting or other interventions. A promising new method in the diagnosis and follow-up of pathologic carotid diseases is contrast-enhanced ultrasound (CEUS). In comparison with magnetic resonance imaging or computed tomography, the contrast agents used for CEUS remain within the vascular space and hence can be used to study vascular disease and could provide additional information on carotid arterial diseases. This review describes the current carotid duplex ultrasound examination and compares the pathologic findings with CEUS.

Stent effects on duplex velocity estimates

BACKGROUND

Doppler-derived velocity criteria used to define the presence and severity of in-stent restenosis after percutaneous angioplasty and endoluminal stenting have been called into question. This study uses an in vitro flow model to examine Doppler-derived velocities after placement of balloon-expandable and self-expanding endoluminal stents (BES and SES).

METHODS

An in vitro vascular circuit model consisting of a pulsatile pump, tubing, and a conduit was created. The pump was programmed to replicate the Doppler spectral waveform pattern of the renal and carotid arteries. Peak systolic velocity (PSV) and end diastolic velocity (EDV) were estimated at five distinct conduit locations. Three replicate velocity measurements were made at each location. After initial velocity estimates, a BES or an SES was deployed within the conduit.

RESULTS

Mean ± standard error PSV was 95.8 ± 2.6 cm/s, 97.0 ± 2.7 cm/s, and 101.4 ± 2.7 cm/s for unstented, BES and SES, respectively. PSV estimates were increased between unstented and stented conduits when SESs were present. The increase in mean systolic velocity of 6.4% observed with SES was statistically significant (P < 0.05). EDV values did not differ significantly across conditions. Mean ± standard error EDV was 36.2 ± 1.0 cm/s, 37.3 ± 1.1 cm/s, and 37.2 ± 1.1 cm/s for unstented, BES, and SES, respectively.

CONCLUSION

The presence of an SES was associated with a less than 7% change in estimated PSV. These results suggest that Doppler velocity estimates for renal and carotid arteries are not materially affected by either BES or SES.

Relations between plasma von Willebrand factor or endothelin-1 and restenosis following carotid artery stenting

OBJECTIVE

This study was designed to investigate the relation between plasma von Willebrand factor (VWF) or endothelin-1 (ET-1) and post-carotid artery stenting (CAS) restenosis.

MATERIALS AND METHODS

Plasma levels of VWF and ET-1 were measured in 61 patients (36 males, mean age 64.4 ± 6.8 years) before and after CAS. The mean follow-up time was 13.8 ± 1.7 months (range, 6-63). In-stent restenosis was defined as a >10% narrowing of the vascular lumen with or without ischemic symptoms following CAS.

RESULTS

In-stent restenosis was identified in 14 (23%) patients, including 3 with >50% restenosis. In the restenosis group, mean VWF and ET-1 levels at 2 weeks, 1 and 6 months after CAS were higher than the baseline levels (p < 0.05 or p < 0.01). Mean levels of VWF and ET-1 in the restenosis group were higher than in the non-restenosis group within 6 months after CAS (p < 0.05 or p < 0.01).

CONCLUSION

Persistent elevation in plasma VWF and ET-1 within the first 6 months of CAS was found in patients with in-stent restenosis.

Comparison of carotid artery stenting in patients with single versus bilateral carotid artery disease and factors affecting midterm outcome

BACKGROUND

Carotid artery stenting (CAS) is the method of choice for carotid artery revascularization of patients at high risk for carotid endarterectomy. In this study, we compared the midterm results of CAS in patients with unilateral versus bilateral carotid artery disease.

METHODS AND RESULTS

This is a retrospective analysis of 1-year outcome of 273 consecutive patients in whom 342 CAS procedures were performed. The incidence of periprocedural transient ischemic attacks (TIAs) differed significantly (8% vs. 1%; p = 0.01) among patients with and without bilateral internal carotid disease, and a tendency to a lower occurrence of early adverse events (death, stroke, periprocedural TIA, periprocedural myocardial infarction) was subsequently shown (11% vs. 5%; p = 0.12). At 1-year follow-up, there was a high incidence of adverse events (death, stroke, periprocedural TIA, periprocedural myocardial infarction, restenosis) in patients with bilateral carotid artery disease (40% vs. 14%; p < 0.01), which was mainly driven by a higher incidence of death, periprocedural TIA, and restenosis (p ≤ 0.02 for all). According to multivariate analysis, the independent predictors of midterm adverse events were left ventricular dysfunction, male gender, bilateral carotid artery disease, renal insufficiency, cerebral symptoms within the last 6 months before the intervention, and low-density lipoprotein cholesterol level.

CONCLUSIONS

At midterm follow-up, patients with bilateral carotid artery disease treated by CAS have significantly more adverse events than those with unilateral disease.

Imaging of carotid arterial diseases with contrast-enhanced ultrasound (CEUS)

Carotid duplex ultrasound is the standard of care for the initial diagnosis of carotid artery bifurcation diseases. But in difficult examinations, carotid abnormalities are commonly encountered and may represent a diagnostic challenge in patients with clinical symptoms as well as in the follow up after carotid endarterectomy or carotid artery stenting. Contrast enhanced ultrasound (CEUS) with low mechanical index (low MI) is a promising new method in the diagnosis and follow up of pathological carotid diseases. Unlike most contrast agents used for magnetic resonance imaging or computed tomography, the microbubbles used in CEUS with SonoVue(®) remain within the vascular space and hence can be used to study vascular disease. In addition to improving current carotid structural scans, CEUS has potential to improve or add extra information on carotid arterial diseases. This review describes the current carotid duplex ultrasound examination and compares the pathological findings with CEUS.

Carotid artery interventions for restenosis after prior stenting: is it different from interventions of de novo lesions? Results from the carotid artery stent (CAS)--registry of the Arbeitsgemeinschaft Leitende Kardiologische Krankenhausärzte (ALKK)

OBJECTIVE

To compare characteristics and outcome of patients with re-stenoses after prior carotid artery stenting (CAS) treated with repeat carotid interventions (Re-CI) with CAS for de novo lesions.

BACKGROUND

The treatment of re-stenosis is a major problem in vascular interventions. Patients with re-stenoses after prior CAS treated with Re-CI are not well defined.

METHODS

We analyzed data from the prospective ALKK CAS Registry.

RESULTS

Out of 3,817 CAS procedures 95 were intended in 93 patients (2.5%) for a restenosis after prior CAS and 3,722 CAS in 3,655 patients (97.5%) for a de novo stenosis. There was no difference in age (p = 0.302) or distribution of gender (p = 0.545) between the two groups. Patients treated for a restenosis after CAS were less likely to be treated for a symptomatic lesion (22.7 vs. 40.1%, p = 0.001). Coronary heart disease (p = 0.017), peripheral arterial disease (p < 0.001) as well as diabetes mellitus (p = 0.004) were more prevalent in the restenosis group. Lesions were less complicated in restenosis patients, with less ulcers (7.4 vs. 19.9%, p = 0.003) and less severe calcifications (7.4 vs. 23.6%, p < 0.001). The intended interventions were more often not performed in the Re-CI group (9.5 vs. 3.3%; p = 0.001). In-hospital, the stroke or death rate was 0% in the Re-CI group as compared to 3.1% in the de novo group (p = 0.115).

CONCLUSIONS

Patients treated with Re-CI for repeat stenoses after prior CAS represent 2.5% of current CAS patients. Although representing a subgroup with more concomitant diseases, Re-CI seems to be associated with lower event rates as compared to CAS for de novo lesions.