Duplex Ultrasound Verified by Angiography in Patients with Severe Primary and Restenosis of Internal Carotid Artery

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.

Color duplex sonography in the detection of internal carotid artery restenosis after carotid endarterectomy: comparison with computed tomographic angiography

OBJECTIVES

Internal carotid artery restenosis after carotid endarterectomy is a major postoperative event, but the clinically best suited means for diagnosis of restenosis are still debated. The objective of this study was to evaluate the sensitivity and specificity of color duplex sonography for detection of substantial internal carotid artery restenosis, verified by computed tomographic (CT) angiography.

METHODS

The study group consisted of 210 consecutive patients with internal carotid artery restenosis, defined as restenosis of 50% or greater, verified by color duplex sonography. The degree of restenosis was calculated according to the European Carotid Surgery Trial guidelines. All patients underwent CT angiography. The specificity, sensitivity, positive predictive value, and negative predictive value of color duplex sonography were calculated.

RESULTS

In 85 patients, internal carotid artery restenosis on color duplex sonography was 50% to 69%, whereas in 125 patients it was 70% or greater. When color duplex sonography was compared with CT angiography, only 2 patients in the group with restenosis of 50% to 69% were misclassified by color duplex sonography, in whom CT angiography showed stenosis of 70% or greater. No patient with stenosis of 70% or greater on color duplex sonography was shown to have a lesser degree of restenosis on CT angiography. When compared with CT angiography, color duplex sonography had specificity of 97.7%, sensitivity of 100%, a positive predictive value of 98.4%, and a negative predictive value of 100% for the detection of internal carotid artery restenosis.

CONCLUSIONS

Color duplex sonography can be effectively used as a primary diagnostic tool for evaluation of patients with suspected internal carotid artery restenosis after carotid endarterectomy.

Results of the Stent-Protected Angioplasty versus Carotid Endarterectomy (SPACE) study to treat symptomatic stenoses at 2 years: a multinational, prospective, randomised trial

BACKGROUND

The SPACE trial is a multinational, prospective, randomised study to test the hypothesis that carotid artery stenting is not inferior to carotid endarterectomy for treating patients with severe symptomatic carotid artery stenosis. We did not prove non-inferiority of carotid artery stenting compared with carotid endarterectomy for the 30-day complication rate, and we now report the results at 2 years.

METHODS

Between March, 2001, and February, 2006, patients with symptomatic, severe (>or=70%) carotid artery stenosis were recruited to this non-inferiority trial and randomly assigned with a block randomisation design to have carotid artery angioplasty with stenting or carotid artery endarterectomy. 2-year endpoints include several clinical endpoints and the incidence of recurrent carotid stenosis of at least 70%. Clinical and vascular follow-up was done by a certified neurologist. Analyses were by intention to treat and per protocol. This trial is registered with ISRCTN, number 57874028.12.

FINDINGS

1 214 patients were randomly assigned (613 were randomly assigned to carotid angioplasty with stenting and 601 were randomly assigned to carotid endarterectomy). In both the intention-to-treat and per-protocol analyses the Kaplan-Meier estimates of ipsilateral ischaemic strokes up to 2 years after the procedure and any periprocedural stroke or death do not differ between the carotid artery stenting and the carotid endarterectomy groups (intention to treat 9.5%vs 8.8%; hazard ratio (HR) 1.10, 95%CI 0.75 to 1.61; log-rank p=0.62; per protocol 9.4%vs 7.8%; HR 1.23, 95%CI 0.82 to 1.83; log-rank p=0.31). In both the intention-to-treat and per-protocol populations, recurrent stenosis of 70% or more is significantly more frequent in the carotid artery stenting group compared with the carotid endarterectomy group, with a life-table estimate of 10.7% versus 4.6% (p=0.0009) and 11.1% versus 4.6% (p=0.0007), respectively. Only two incidences of recurrent stenoses after carotid artery stenting led to neurological symptoms.

INTERPRETATION

After 2 years' follow-up, the rate of recurrent ipsilateral ischaemic strokes reported in the SPACE trial is similar for both treatment groups. The incidence of recurrent carotid stenosis at 2 years, as defined by ultrasound, is significantly higher after carotid artery stenting. However, it cannot be excluded that the degree of in-stent stenosis is slightly overestimated by conventional ultrasound criteria.

Characteristic sonographic findings of early restenosis after carotid endarterectomy

OBJECTIVE

Restenosis of the carotid artery after carotid endarterectomy (CEA) is a major complication. The frequency, time of occurrence, and tissue characteristics of carotid restenosis were assessed with sonography.

METHODS

Two hundred sixteen patients who had CEA for carotid stenosis were studied; follow-up sonography and magnetic resonance angiography were done 2 weeks, 3 months, and then every year after CEA. On sonography, restenosis was defined as an internal carotid artery (ICA) with a peak systolic velocity of 170 cm/s or greater or a maximum area of stenosis of 90% or greater.

RESULTS

During 605 artery-years of follow-up, 18 patients (7.5%) were found to have restenosis on sonography: 4 at 3 months, 11 at 1 year, and 3 at 2 years after CEA. At the time that restenosis was detected, in all 18 ICAs the peak systolic velocity exceeded 200 cm/s and had more than doubled since the last measurement (mean +/- SD, 103 +/- 27 to 321 +/-107 cm/s), whereas the area of stenosis exceeded 90% in 6 patients, and magnetic resonance angiography revealed stenosis of 60% or greater in 8 patients. On sonography, all of the restenotic plaques were isoechoic and concentric. The restenosis was asymptomatic in 17 patients. Vascular risk factors or the severity of initial carotid stenosis before CEA were not associated with development of restenosis. Eleven patients had successful endovascular therapy, and the others received medical treatment.

CONCLUSIONS

A marked increase in the flow velocity through an operated ICA is a good indication of restenosis. The isoechogenicity and concentricity of the restenotic plaques suggest that the restenosis is primarily the result of intimal hyperplasia.

Advances in vascular imaging

Advances in vascular surgery have mirrored advances in diagnostic imaging. Indeed, the endovascular revolution has been made possible largely by advances in computed tomography, magnetic resonance imaging, and vascular ultrasound. As technology allows better noninvasive vascular diagnosis, conventional angiography, once the gold standard for the diagnosis of vascular disease, is now reserved largely for intervention. This article discusses the current state of vascular imaging. Specific emphasis is placed on the comparative clinical utility of different imaging modalities in the detection and management of vascular disease.

Blood-borne tissue factor activity predicts major cerebrovascular events in patients undergoing carotid endarterectomy: results from a 1-year follow-up study

BACKGROUND

Tissue factor (TF) expression is increased in inflammatory atherosclerotic plaques and has been related to plaque thrombogenicity. Blood-borne TF activity seems to contribute to a procoagulant state in patients with vascular risk factors. The aim of this study was to assess whether the expression of TF in carotid plaques from patients undergoing carotid endarterectomy (CEA) or/and blood-borne ('circulating') TF activity could predict future vascular complications.

METHODS

A total of 105 consecutive patients (85 male and 20 female aged 61-77 years)undergoing CEA for high-grade internal carotid artery were included in the study. Carotid artery specimens were classified into active (n = 52; rich in inflammatory cells) and nonactive plaques (n = 53; poor in inflammatory cells or fibrous). TF mRNA levels in carotid plaques were assessed by real-time PCR (TaqMan Low-Density Arrays) and TF protein levels by Western blot. Blood-borne TF activity and other biochemical parameters, including low-density lipoprotein cholesterol (LDLc) levels and high-sensitivity C-reactive protein, were measured prior to surgery. Patients were followed up for 1 year and vascular and nonvascular complications were scored.

RESULTS

TF expression was higher in active CEA plaques. Patients with active CEA plaques exhibited higher plasma LDLc levels (3.6 +/- 0.7 vs. 2.1 +/- 1 mM, p < 0.05) that positively correlated with plaque TF mRNA levels (p = 0.0125; r = 0.9). Blood-borne TF activity did not correlate with plasma LDLc levels and was unrelated to the anatomo-pathological characteristic of the CEA plaques (thrombosis, rupture, inflammation, lipid core, necrosis or calcification). Circulating TF activity predicted vascular complications at 1 year, including fatal (OR, 1.18; 95% CI, 0.6-2.2, p < 0.01) and nonfatal ischemic stroke (OR, 1.22; 95% CI, 0.5-2.0, p < 0.05) and symptomatic peripheral vascular disease (OR, 1.48; 95% CI, 0.4-2.6, p < 0.005).

CONCLUSIONS

Blood-borne TF activity prior to CEA but not local TF expression or plasma LDLc levels predict cerebrovascular and peripheral vascular disease events at 1 year in elderly patients subjected to CEA for high-grade carotid stenosis.

Carotid artery velocity characteristics after carotid artery angioplasty and stenting

OBJECTIVE

Correlation of carotid duplex ultrasound (DUS) flow velocities with carotid artery stenosis before and after carotid endarterectomy is well established. With the evolution of catheter-based techniques, carotid stenosis increasingly is being treated with angioplasty and stenting (CAS). CAS changes the physical properties of the arterial wall, which may alter blood flow velocities compared with the nonstented carotid. Opinions differ about whether DUS is a reliable tool to assess technical outcome and recurrent stenosis after CAS. This study correlated carotid DUS flow velocity findings with carotid arteriography after CAS.

METHODS

Data from 77 pairs of carotid arteriograms with corresponding DUS after CAS in 68 patients were reviewed. Preintervention and postintervention DUS and carotid arteriogram data were evaluated for each patient. Peak systolic velocities (PSV), end-diastolic velocities (EDV), and internal carotid artery/common carotid artery ratios (ICA/CCA) were correlated with the post-CAS arteriogram.

RESULTS

The mean preintervention PSV was 390 +/- 110 cm/s (range, 216 to 691 cm/s), and the average EDV was 134 +/- 51 cm/s (range, 35 to 314 cm/s). Postintervention DUS was obtained a mean of 5 days after CAS (range, 1 to 30 days). Sixty (81%) post-CAS arteriograms were normal, and each corresponded to a normal postintervention DUS (PSV range, 30 to 118 cm/s; EDV range, 18 to 60 cm/s). In 14 arteries (19%), completion arteriograms revealed residual stenoses of 20% to 40% in 13, and 50% in one. The mean PSV was 175 cm/s (range, 137 to 195 cm/s), and the mean EDV was 44 cm/s (range, 20 to 62 cm/s). All velocities exceeded the threshold of a 50% stenosis by DUS criteria for a nonstented carotid artery. In three arteries (2 patients), high-grade recurrent stenoses detected by DUS developed that required reintervention during follow-up. This high-grade restenosis was confirmed by arteriography in each patient, providing an additional three correlations.

CONCLUSIONS

Normal DUS imaging reliably identifies arteriographically normal carotid arteries after CAS. Carotid velocities are disproportionately elevated with mild and moderate degrees of stenoses, and velocity criteria for quantitating stenoses in these patients require modification. However, DUS appropriately identifies severe recurrent stenoses after CAS.