Surveillance imaging for carotid in-stent restenosis

The management of carotid restenosis: a comprehensive review

Carotid artery stenosis (CS) is a major medical problem affecting approximately 10% of the general population 80 years or older and causes stroke in approximately 10% of all ischemic events. In patients with symptomatic, moderate-to-severe CS, carotid endarterectomy (CEA) and carotid angioplasty and stenting (CAS), has been used to lower the risk of stroke. In primary CS, CEA was found to be superior to best medical therapy (BMT) according to 3 large randomized controlled trials (RCT). Following CEA and CAS, restenosis remains an unsolved problem involving a large number of patients as the current treatment recommendations are not as clear as those for primary stenosis. Several studies have evaluated the risk of restenosis, reporting an incidence ranging from 5% to 22% after CEA and an in-stent restenosis (ISR) rate ranging from 2.7% to 33%. Treatment and optimal management of this disease process, however, is a matter of ongoing debate, and, given the dearth of level 1evidence for the management of these conditions, the relevant guidelines lack clarity. Moreover, the incidence rates of stroke and complications in patients with carotid stenosis are derived from studies that did not use contemporary techniques and materials. Rapidly changing guidelines, updated techniques, and materials, and modern medical treatments make actual incidence rates barely comparable to previous ones. For these reasons, RCTs are critical for determining whether these patients should be treated with more aggressive treatments additional to BMT and identifying those patients indicated for surgical or endovascular treatments. This review summarizes the current evidence and controversies concerning the risks, causes, current treatment options, and prognoses in patients with restenosis after CEA or CAS.

Restenosis after carotid artery stenting

As a common etiology for ischemic stroke, atherosclerotic carotid stenosis has been targeted by vascular surgery since 1950s. Compared with carotid endarterectomy, carotid angioplasty and stenting (CAS) is almost similarly efficacious and less invasive. These advantages make CAS an alternative in treating carotid stenosis. However, accumulative evidences suggested that the long-term benefit-risk ratio of CAS may be decreased or even neutralized by the complications related to in-stent restenosis (ISR). Therefore, investigating the mechanisms and identifying the influential factors of ISR are of vital importance for improving the long-term outcomes of CAS. As responses to intrinsic and extrinsic injuries, intimal hyperplasia and vascular smooth muscle cell proliferation have been regarded as the principle mechanisms for ISR development. Due to the lack of consensus-based definition and consistent follow-up protocol, the reported incidences of ISR after CAS varied widely among studies. These variations made the inter-study comparisons of ISR largely illogical. To eliminate restenosis after CAS, both surgery and endovascular procedures have been attempted with promising results. For preventing ISR, drug-eluting stents and antiplatelets have been proposed as potential solutions.

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.

State of the art in carotid artery stenting: trial data, technical aspects, and limitations

The volume of carotid artery stenting (CAS) safety and efficacy data has grown exponentially over the last decade. Recent comparative data with carotid endarterectomy, the utility of embolic protection devices, peri-procedural medications, basic technical aspects of CAS, developments in carotid stent design, potential complications of CAS, and complication risk factors are discussed in this review.

Frequency and consequences of early in-stent lesions after carotid artery stent placement

PURPOSE

To examine the prevalence of in-stent lesions 1 month after carotid artery stent placement with multidetector computed tomography (CT) angiography and to evaluate their possible causes and their consequences during 1-year follow-up.

MATERIALS AND METHODS

Sixty-nine patients with symptomatic carotid artery stenosis underwent multidetector CT angiography of the carotid arteries 1 month after carotid artery stent placement. Patients were followed-up until 1 year after stent placement, when duplex ultrasonography (US) was performed. In-stent lesions were defined as hypo- or hyperattenuating lesions at the stent wall found with multidetector CT. Significant restenosis (70%) at 1 year was defined as a peak systolic velocity of more than 300 cm/sec at duplex US. The Fisher exact test was used to assess the relationship between early in-stent lesions and ischemic events and restenosis.

RESULTS

At 1 month, 14 of the 69 patients (20%) were found to have in-stent lesions. In one patient, the stent was occluded. The other 13 in-stent lesions did not result in significant lumen reduction. In the year following stent placement, no difference in ischemic events was found between patients with (14%) and those without (13%) early in-stent lesions (P = .99). There was no difference in the occurrence of restenosis at 1 year (7% vs 4%, P = .59).

CONCLUSIONS

At 1 month after carotid artery stent placement, in-stent lesions are found in about one-fifth of patients. These lesions do not appear to be related to recurrent ischemic events or to restenosis at 1 year.

Cutting balloon angioplasty for carotid in-stent restenosis: case reports and review of the literature

Percutaneous stenting techniques are becoming more commonly used for treatment of carotid artery disease. One outcome of particular concern is in-stent restenosis. Indications for treatment of in-stent restenosis are not clearly defined. Use of traditional balloon angioplasty with or without stent placement is still considered the first option. Cutting balloon angioplasty has recently been used as an alternative treatment option for revascularization of in-stent restenosis with higher procedural success rates and without the use of additional stents. We report our experience with cutting balloon angioplasty in treating 2 patients with carotid in-stent restonosis, and review previous cases reported in the literature. A total of 16 patients have been treated with cutting balloon angioplasty. Among 11 patients for whom the clinical and angiographic information were available, 63% of patients were asymptomatic at the time of treatment, and more than 90% of patients showed either complete angiographic resolution or residual stenosis of less than 30%. Additional stent placement or angioplasty was required in only half of the patients, and 1 patient had recurrent stenosis. The review suggests that the procedure is safe and effective.

Carotid artery stent type influences duplex ultrasonography derived peak systolic velocity: findings of an in-vitro model

OBJECTIVE

The goal of this study is to evaluate the effect of stenting on Doppler ultrasonography (DU) [velocity] signals in an in-vitro carotid model.

BACKGROUND

Considerable debate exists about whether DU overestimates velocity signals and thus the degree of stenosis in previously stented carotid arteries.

METHODS

Constant, pulsatile flow was simulated with an experimental circulatory system containing a nonstenotic ovine internal carotid artery segment. Peak systolic velocity (PSV) and peak diastolic velocity were measured with an intravascular flow wire (FW) and DU. Velocities were evaluated at five predetermined locations within the vessel immediately prior to and following stent placement.

RESULTS

Eleven stents were implanted. DU-derived PSV increased significantly following placement of the X-Act stent (80+/-26 cm/sec [pre] vs. 102+/-29 cm/sec [post], P=0.02), while FW-derived PSV (65+/-23 cm/sec [pre] vs. 66+/-9 cm/sec [post], P=0.93) did not change. The Precise stent did not influence PSV with either method (DU: 76+/-28 cm/sec [pre] vs. 72+/-35 cm/sec [post], P=0.95;), while the Acculink stent showed a trend towards a reduction in DU (69+/-37 cm/sec [pre] vs. 51+/-10 cm/sec [post], P=0.075) and FW (50+/-27 cm/sec [pre] vs. 40+/-12 cm/sec [post], P=0.14) derived PSV. Peak diastolic velocity revealed similar trends as PSV signals depending on the type of stent used.

CONCLUSIONS

Stent type may have significant impact on DU derived velocity signals. DU seems to overestimate PSV in carotid arteries treated with the X-Act stent, but not with the Precise or Acculink stent. Larger scale clinical comparison of various stent types and their impact on DU are needed in order to clarify the value of DU surveillance following carotid artery stenting.

Covered stent-graft treatment of traumatic internal carotid artery pseudoaneurysms: a review

OBJECTIVE

To review the literature concerning the management with placement of covered stent-grafts of traumatic pseudoaneurysms of the extracranial internal carotid artery (ICA) resulting from penetrating craniocervical injuries or skull base fractures.

METHOD

We have reviewed, from the Medline database, all the published cases in the English literature since 1990 and we have added a new case.

RESULTS

We identified 20 patients with traumatic extracranial ICA pseudoaneurysms due to penetrating craniocervical injuries or skull base fractures who had been treated with covered stent-graft implantation. Many discrepancies have been ascertained regarding the anticoagulation therapy. In 3 patients the ICA was totally occluded in the follow-up period, giving an overall occlusion rate 15%. No serious complication was reported as a result of the endovascular procedure.

CONCLUSION

Preliminary results suggest that placement of stent-grafts is a safe and effective method of treating ICA traumatic pseudoaneurysms resulting from penetrating craniocervical injuries or skull base fractures. The immediate results are satisfactory when the procedure takes place with appropriate anticoagulation therapy. The periprocedural morbidity and mortality and the early patency are also acceptable. A surveillance program with appropriate interventions to manage restenosis may improve the long-term patency.

Predictors of carotid stent restenosis

OBJECTIVES

We sought to determine the predictors of restenosis after carotid artery stenting and report alternatives for its management.

BACKGROUND

Carotid artery stenting has been increasingly accepted as an alternative to carotid endarterectomy (CEA). Predictors of carotid stent restenosis have not been firmly established, and management of restenotic lesions can be challenging.

METHODS

A retrospective, single-center review was conducted of 399 carotid stent procedures in 363 patients over 9 years, with a mean follow-up of 24 months (range 6-99 months). Clinical variables included age, gender, symptoms, hypertension, diabetes, tobacco use, renal insufficiency, coronary artery disease, hyperlipidemia, peripheral vascular disease, history of CEA, and history of neck radiation (XRT). Angiographic variables included reference vessel diameter, lesion length, post-stenting residual stenosis, stent diameter, type of stent, and number of stents.

RESULTS

Overall, restenosis occurred in 15 patients (3.8%). However, the restenosis occurred in 7 of 35 (20%) patients who had previous XRT, 6 of 57 (10.5%) patients who had previous CEA, and 2 of 9 (22%) patients who previously had both CEA and XRT. The only analyzed variables that were significantly associated with an increased risk of restenosis were previous CEA (OR 4.28, P = 0.008) or XRT (OR 11.3, P <or=<or= 0.0001). Restenosis was most often asymptomatic and detected at routine ultrasound follow-up. Restenotic lesions were successfully treated in 11/11 cases with angioplasty (27%) or stenting (73%). Four patients that are asymptomatic are being monitored closely with ultrasound. No patients required surgical therapy for restenosis.

CONCLUSIONS

Restenosis after carotid stenting is uncommon; however, patients with previous CEA or XRT are at increased risk. Restenotic lesions may be safely treated with further percutaneous interventions.