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Haneen Habib Al Aali1

Author affiliations
1RCSI – Medical University of Bahrain medical student

Royal College of Surgeons in Ireland Student Medical Journal 2012;5: 28-32.

Abstract
Background: Carotid angioplasty with stenting is becoming a more popular treatment option for severe carotid occlusive disease. It is accepted as a less invasive technique than carotid endarterectomy and may provide an alternative for select patients, particularly those with significant comorbidities. Carotid artery stenting has been performed in Bahrain since 2006, but no studies have been conducted to evaluate its safety and effectiveness. This study aims to evaluate the feasibility, safety and efficacy of carotid artery stenting in Bahrain.
Methods: We conducted a retrospective case series to review patients who underwent carotid artery angioplasty with stenting at the Sheikh Mohammed Bin Khalifa Bin Salman Al Khalifa Cardiac Centre in the Bahrain Defense Hospital. We studied the demographic, lesion and procedural characteristics of patients and followed the patients for six months. Procedural success was defined as residual diameter stenosis of less than 30% in stented patients. The end points were death, stroke, myocardial infarction or transient ischaemic attack within 30 days or after six months of treatment.
Results: We performed 57 carotid angioplasty and stenting procedures in 47 patients (32 men and 15 women). The mean stenosis before stenting was 83.7% (σ=11.3%) and after stenting was 4.5% (σ=7%). Procedural success was achieved in 55 (96.5%) of the 57 interventions, with two unsuccessful procedures. The end points occurred in two out of the 57 cases within 30 days and in seven cases at six months. In the 30-day post-procedural period, there was one case of myocardial infarction (1.8%) and one case of transient ischaemic attack (1.8%). At six months of clinical follow-up, two patients (3.7%) had passed away and five (9.3%) myocardial infarctions had occurred. In all cases of myocardial infarction, the patients had a history of coronary artery disease before undergoing the carotid stenting. There were no complications with any of the procedures and the restenosis rate at six months for the lesion was 0%. Procedural failure due to inability to cross the lesion was reported in only one case.
Conclusions: Carotid artery stenting is a feasible, safe and effective treatment of carotid occlusive disease among patients with severe carotid artery stenosis. Long-term follow-up is recommended to determine whether the outcomes of this procedure are sustained.
Key words: stroke; carotid artery stenting; percutaneous transluminal angioplasty; transient ischaemic attack; myocardial infarction.


Introduction

The incidence of stroke in Bahrain is 57 per 100,000 individuals.1 Large artery atherosclerosis is the most common cause of stroke in the Arabian peninsula.2 The incidence of asymptomatic atherosclerotic carotid artery stenosis increases with age. Carotid artery atherosclerosis is a potentially preventable and treatable process – an important fact given that it is a significant risk factor for the development of ischaemic stroke. Carotid endarterectomy (CEA) is considered the gold standard treatment for carotid artery occlusive disease.3 However, the approach carries significant complications that make it applicable only to treatment of surgically accessible stenoses of the bifurcation of the common or internal carotid arteries.4 These complications include cranial nerve injury, wound haematoma, hypotension, hyperperfusion syndrome, intracranial haemorrhage, seizures and recurrent stenosis. During the past decade, carotid angioplasty with stenting (CAS) has been used as an alternative to CEA in patients of high surgical risk. The treatment goal of CAS is to eliminate carotid artery stenosis and to prevent embolism and stroke. CAS was introduced in Bahrain in February 2006 at the Sheikh Mohammed Bin Khalifa Bin Salman Al Khalifa Cardiac Centre in the Bahrain Defense Hospital (BDF-MKCC).

A femoral approach is used for CAS, where a flexible sheath (6-7 French) or, less commonly, a guiding catheter (8-9 French) is inserted into the common carotid artery using an Amplatz SuperStiffTM guidewire that has been placed in the external carotid artery (Figure 1a). The lesion is crossed and a distal embolic device is positioned. Predilatation is performed only if it is felt that the filter or the stent cannot be advanced without it. One or more dedicated self-expanding stents are then deployed across the lesion and dilated to a diameter equal to that of the artery. The stent acts as scaffolding to prevent the artery from collapsing or being occluded by plaque after the procedure is completed. Following stent deployment, contrast is injected to confirm patency and assess proper positioning. The angiogram is repeated for final confirmation of a satisfactory result and the filter sequestering the captured emboli is collapsed and removed.5

FIGURE 1: (a) Amplatz Super StiffTM Guide Wire; (b) FilterWire EZTM Embolic Protection Device (Boston Scientific; Natick, MA, USA).11

The patient is fully awake during the procedure with little or no sedation, as constant neurologic monitoring is essential.6 The common femoral vein is accessed in order to facilitate prompt infusion of atropine, norepinephrine and fluid as required if the carotid sinus barorecepter reflex is activated.7 The incidence of the haemodynamic instability is lower if the balloon does not stretch the carotid sinus.8 Factors that increase the risk of complications during CAS include: hypertension; an allergy to contrast dye; dense calcifications and severe stenosis of the carotid artery; sharp bends or other difficult anatomy of the carotid arteries; irregular-looking plaque, significant plaque or atherosclerosis of the aorta near the beginning of the carotid artery; increasing age (80+ years); extensive blockages in the femoral or brachial arteries; and, poor kidney function.9

Despite being less invasive, CAS has more than eight times the intraprocedural risk of microemboli of CEA when evaluated with transcranial Doppler.10 For this reason, devices must be used to decrease the incidence of intracranial particulate debris embolisation during CAS. There are three different classes of distal embolic devices: balloon occluders; filters; and, circulatory control devices (Figure 1b), all of which are designed to prevent intraprocedural microembolisation.11 Several randomised trials have been conducted worldwide to study the efficacy of CAS and CEA in asymptomatic and symptomatic patients with the goal to help define the role of both interventions and inform best practice guidelines.12-14 However, more studies with reliable data are required to determine the relative efficacy, restenosis rate and suitability of CAS as compared to CEA.15

We conducted this retrospective case series to analyse the outcomes of CAS at BDF-MKCC, and to evaluate the safety and effectiveness of CAS in a series of patients with carotid artery stenosis.

Methods

Patient eligibility and inclusion criteria
We retrospectively reviewed the medical charts of patients who underwent CAS in BDF-MKCC from February 2006 to February 2010. Patient eligibility for CAS required at least a 70% stenosis of the carotid artery documented by intracranial angiography and fulfilment of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria.16 All patients who presented with symptomatic carotid artery disease and who were considered to be at high surgical risk were approved for CAS. High-risk characteristics for CEA include: contralateral carotid occlusion; ostial common carotid lesions (i.e., in close proximity to artery bifurcation); severe cardiac or pulmonary disease; prior CEA; prior neck radiation; prior radical neck dissection; and, stenosis involving the ipsilateral siphon (tandem lesions).17 Patients with asymptomatic carotid artery disease – that is, the presence of significant atherosclerotic build-up (>80%) without accompanying symptoms – were considered high-risk.18

Radiological evaluation
Diagnostic studies included Doppler ultrasonography and magnetic resonance imaging (MRI) of the brain, which were performed to determine the extent of any previous infarctions and to rule out structural abnormalities and intracranial haemorrhage. The status of carotid and vertebral arteries was studied bilaterally before conducting the procedure. Patients’ demographic characteristics, factors predisposing to neurological complications, previous history of stroke or transient ischaemic attack (TIA), previous medications and secondary prevention therapies were documented.

Pharmacological considerations
Patients received 325mg aspirin and 75mg clopidogrel daily, starting at least one week and five days before their scheduled procedure, respectively. Clopidogrel was administered for four to six weeks after the procedure, and low-dose aspirin was continued indefinitely.19 Heparin (100U/kg) was administered during the procedure to maintain an activated clotting time of 200-250 seconds.

Patient outcomes
On day one post procedure, patients underwent a Doppler echocardiographic study and neurological examination, including administration of the National Institutes of Health Stroke Scale (NIHSS) and a full physical assessment. This full assessment was repeated on day 30 and six months post procedure. Procedural success was defined as residual diameter stenosis <30% in stented patients. The end points studied were death, stroke, myocardial infarction (MI) or TIA after the CAS. Stroke was defined as an ischaemic neurologic deficit that persisted for more than 24 hours. MI was defined as a creatine kinase level higher than two times the upper limit of normal with a positive MB fraction. TIA was defined as a focal deficit lasting less than 24 hours, from which there is complete neurological recovery.

Results

Patient demographics and clinical characteristics
We performed 57 carotid angioplasty and stenting procedures in 47 patients (32 male, 15 female) at BDF-MKCC. All 47 patients were followed and the baseline clinical characteristics of the patients were compared (Table 1). The mean age was 68 years (σ=9.9), ranging from 45 to 87 years. Ten patients underwent bilateral interventions as planned by the consultant physician.


Table 1. (Click to enlarge.)

The major risk factors in these patients were hypertension (n=49; 86.0%), diabetes (n=40; 70.2%) and hypercholesterolaemia (n=43; 75.4%). Thirteen patients (22.8%) were smokers at the time of intervention. Thirty-nine (68.4%) had coronary artery disease (CAD) and 19 (33.35%) had a history of TIA. Eight patients (14%) had a history of stroke. Ten patients (17.5%) had undergone previous percutaneous coronary intervention, and ten (17.5%) had previously undergone coronary artery bypass surgery.

Procedural and angiographic data
Twenty patients had obstructions in the right carotid, all of which involved the right internal carotid artery (RICA). Twenty-seven patients had stenosis of the left carotid artery – 25 in the left internal carotid artery (LICA) and two in the left common carotid artery (Table 2). The mean stenosis before stenting was 83.7% (σ=11.3%). Two arteries were sub-totally occluded. Among the stented patients, procedural success was achieved in 55 (96.5%), with the mean residual stenosis of 4.5% (σ=7%) (Table 3). Of the 57 procedures followed, two interventions were unsuccessful. In one case, stenting of the LICA was aborted after the patient developed acute chest pain, and the procedure was repeated two months later with successful angiographic results (Figure 2). The second unsuccessful case was due to the inability to cross the lesion with the guidewire due to tortuous and ulcerated stenosis of the RICA; the patient eventually required CEA.


Table 2. (Click to enlarge.)


Table 3. (Click to enlarge.)

FIGURE 2: Angiographic evidence of success before and after carotid artery angioplasty with stenting of the left internal carotid artery in an asymptomatic patient whose occlusion was believed to be secondary to radiation.

End points
End points were observed in two of the 57 cases within 30 days and in seven cases at six months. We were not able to locate follow-up reports on three patients at six months, and thus they were excluded from the results. Within 30 days, there was one MI in a 79-year-old patient whose medical history was positive for diabetes mellitus, hypertension, dyslipidaemia and smoking. One TIA was documented within the 30-day period in an 84-year-old male who subsequently underwent CEA one month later. At six months, there were five documented cases of MI and two deaths due to unrelated causes. All six patients who suffered MIs during the observation period had previously presented to hospital with CAD before the intervention (Table 4).


Table 4. (Click to enlarge.)

Discussion

Historically, the primary treatment modality for occlusive carotid artery disease has been medical management with or without CEA. Medical therapy includes strict risk factor modification, including antihypertensive therapy, lipid management, smoking cessation, exercise, weight control and anti-platelet therapy.20 However, CEA continues to be the treatment of choice in symptomatic patients with more than 70% carotid artery stenosis. Several major randomised trials concerning the surgical treatment of carotid artery stenosis have shown that CEA is superior to medical treatment in reducing the overall risk of stroke in symptomatic and asymptomatic patients.3,21,22 Technological advances have allowed for the evolution of treatment through less invasive therapeutic modalities using balloon angioplasty and stents. Additionally, the use of mechanical cerebral protection devices in conjunction with CAS demonstrably reduces embolisation risk and is considered the standard of care when performing these procedures.23,24

Angioplasty with stenting has many advantages over CEA. Stenting is performed under local anaesthesia, thus permitting continuous neurological monitoring and increasing patient safety. It is minimally invasive, involving a small opening that is less than 3mm in diameter in the femoral artery. Direct surgical exposure of the neck vessels, as required in CEA, increases the risk of wound infection, cranial nerve deficit, vocal cord paralysis, hoarseness and dysphagia. The complete recovery time in CAS averages two to four days, whereas CEA recovery time requires up to four weeks.25

Several clinical trials have studied the outcome of CAS with the use of a distal protection device compared to traditional CEA.26-30 The Carotid And Vertebral Artery Transluminal Angioplasty Study (CAVATAS) randomly assigned 504 patients to either angioplasty, angioplasty with stenting or surgery. Only 26% of participants received a stent. The 30-day risk of stroke or death was 10% in all groups. Of note, the patient group that underwent CEA experienced a higher incidence of cranial nerve palsies (8.7% in the CEA group vs. 0% in the angioplasty group) and haematomas requiring treatment.26

Roubin et al. published a series of 528 consecutive patients treated with stent-supported carotid artery angioplasty between 1994 and 1999 – before cerebral protection devices were readily available. Three-year follow-up data were available for 518 patients. Technical success was achieved in 98% of cases, with a 30-day post-procedure incidence of death, non-fatal major strokes and minor strokes of 1.6%, 1.0% and 4.8%, respectively.27

The Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial demonstrated a significant advantage for CAS with emboli-deterring devices. The primary end point (cumulative incidence of death, stroke or MI within 30 days post intervention, or death or ipsilateral stroke between 31 days and one year post intervention) occurred in 20 CAS patients (12.2%) and 32 CEA patients (20.1%) (p<0.05). Most of the benefit was detected in the lower risk of MI with CAS compared to CEA.28 Conversely, the EVA-3S trial found that patients with symptomatic carotid artery stenosis of 60% or more who underwent CEA had lower rates of death and stroke at one and six months than those who underwent CAS.29 The NIH-funded Carotid Revascularisation Endarterectomy versus Stenting Trial (CREST) is the largest prospective randomised trial to date that compares CEA and CAS, enrolling 2,502 patients from 117 US and Canadian centres.30 The overall safety and efficacy of CAS and CEA was largely the same, with equal benefits for men and women, and for patients with or without a history of stroke. No significant difference was seen between CAS and CEA in the composite primary endpoint of stroke, MI or death in the peri-procedural period or ipsilateral stroke on follow-up. However, it was found that more MIs occurred with CEA (2.3%) than with CAS (1.1%) (p<0.05). Conversely, there were more strokes in CAS patients (4.1%) than with CEA patients (2.3%) (p<0.05). The study also found that the age of the patient significantly impacted on outcome. In patients aged 69 or younger, CAS results were slightly better, and the benefit of CAS increased the younger the patient was. For patients aged 70 or older, CEA results were slightly superior to those of CAS, and the superiority of CEA outcomes increased with age. In this retrospective case series, the results of CAS with a cerebral protection device in BDF-MKCC indicate a low incidence of adverse events at 30 days and six months post procedure. Procedural failure due to inability to cross the lesion was reported in only one of 57 cases. There were no complications encountered otherwise, and no restenosis was witnessed by six months. Based on these findings, CAS is a feasible, safe and effective treatment of carotid occlusive disease in patients who have a high surgical risk or have inoperable lesions. Limitations of this study include a small sample size and the inclusion of data from a single centre. The sample size limits the power of the study, and reduces the ability to detect subtle trends in the group. Another limitation of this study is that it was a retrospective analysis performed in a single medical centre. Thus, the findings cannot be generalised due to referral and selection bias, variable physician expertise and multidisciplinary care. Furthermore, there was no control group of CEA patients to compare outcomes. Finally, long-term follow-up is necessary to further investigate restenosis and outcome sustainability.

Conclusion

CAS is a feasible and safe treatment for carotid artery disease, and is a good alternative to CEA in patients with inoperable lesions or those with high surgical risk. Several large, high-quality studies have demonstrated that CAS is at least as safe as CEA. Further studies are needed to conclusively evaluate factors that are predictive of carotid stent restenosis and to determine whether different stent designs, sizes or deployment techniques might affect the outcome of CAS interventions.

Acknowledgements

The author is indebted to Dr Husam Noor, interventional cardiologist, for his advice and support of this study.

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