ACST-2
HTA/BUPA Foundation/University of Oxford

ACST-2

Asymptomatic Carotid Surgery Trial (ACST)

Asymptomatic Carotid

Surgery Trial (ACST-2)

A large, simple randomised trial to compare
carotid endarterectomy versus carotid artery stenting to prevent stroke

If a patient needs a procedural intervention for asymptomatic carotid stenosis, there may be substantial uncertainty whether to opt for carotid endarterectomy (CEA) or carotid artery stenting (CAS). ACST-2 seeks to randomise such individuals between CEA and CAS to compare both the immediate hazards of the two procedures when done by experienced doctors, and the subsequent stroke rates over the next 5 to 10 years. ACST-1 (1993-2003) was a trial of CEA versus no immediate procedure (showing CEA could be effective), and involved 3000 patients. Its successor, ACST-2, can succeed only if many thousands of patients are randomised. Hence, the workload per patient is minimised, so that the study can be integrated easily into routine health care. The protocol and all forms are available on www.acst.org.uk

Eligibility:  Patient has asymptomatic carotid artery stenosis that is thought to need some procedural intervention; angiography shows CEA and CAS are both anatomically practicable; but, both doctor and patient are substantially uncertain whether CEA or CAS is preferable.

Information and consent:  If (perhaps even before any magnetic resonance, CT or other angiography) you think a patient might well be eligible, then mention the study to the patient and give the information leaflet for the patient to take away for consideration. The consent section of the information leaflet requires contact details of the patient (for an annual letter from the trial centre) and of the family doctor and 1 or 2 friends or relatives (in case contact is lost).

Randomisation:  After consent has been signed, complete at least the first half of the 1-page randomisation form before calling the 24-hour randomisation number +44 (0)18 65 76 56 15 to obtain the treatment allocation (CEA or CAS) and the 6-digit patient ID. This call takes about 2 minutes. Plan for the allocated procedure (CEA or CAS) to be done soon.

Treatment and 1-month post-procedural follow-up:  The allocated procedure must be done by a collaborator whose Track Record for that procedure has been approved. Review the patient 1 month afterwards and complete a short form to describe carotid patency and any peri- or post-procedural events.

Long-term follow-up:  Annual follow-up for at least 5 years (to monitor any strokes) will be by the ACST office writing to the patient.  After the 1-month post-procedural form, no further follow-up by the doctor is required (unless fuller details of a self-reported stroke need to be provided).

As the study is so easy, many hundreds of doctors and many thousands of patients can take part, and uniquely reliable evidence will then emerge comparing the immediate and the long-term safety of CEA and CAS. If a few thousand patients are randomised the results will be useful; if several thousand are randomised the results will be more useful; and if really large numbers are randomised then the results could affect the treatment of millions of patients in future decades.

Asymptomatic carotid artery stenosis?

Substantially uncertain whether to treat with
carotid endarterectomy or carotid artery stenting?

CONSIDER FOR ACST-2

ACST-2 Protocol: Version 4.2, December 2007 (UK MREC approval no. 05Q0201/66) ISRCTN21144362 

ACST-2: NIHR HTA/BUPA Foundation/University of Oxford
Asymptomatic Carotid Surgery Trial

To enquire about the trial,

contact the ACST office:

ACST, Dept. of Cardiac & Vascular Sciences

St George’s University of London, SW17 0RE, UK

email: acst@sgul.ac.uk

tel: +44 (0) 20 87 25 37 46

fax: +44 (0) 20 87 25 37 82

To RANDOMISE a patient, telephone
+44 (0) 18 65 76 56 15

ACST-2 PROTOCOL

Contents

Appendices

Protocol Summary

ACST-2

Background

Atherosclerotic narrowing of the carotid arteries can cause stroke, and about 100,000 people in the UK and at least one million people in Europe alone have severe stenosis (narrowing) in one or both of the carotid arteries in their neck1, 2. 

Treatments for patients with carotid artery stenosis

Medical treatment: Appropriate medical treatment with anti-platelet, anti-hypertensive and cholesterol-lowering medicines helps to prevent both heart attack and stroke. In addition, if there is carotid stenosis then non-pharmacological interventional procedures (surgery or stenting) can be used to reduce still further the risk that it will cause a stroke over the next few years.

Carotid endarterectomy (CEA):  In 1991 two large trials of surgery (CEA) to remove carotid artery stenosis in ‘symptomatic’ patients (ie, those who had had a stroke or stroke-like symptoms within the last few months, irrespective of whether any symptoms still persisted) showed that CEA reduced the risk of future stroke from that stenosis3,4.  CEA is now widely used for stroke prevention in symptomatic patients.  The first Asymptomatic Carotid Surgery Trial (ACST-1)5 and a parallel trial in North America6 then investigated the role of CEA in a total of 5000 patients with carotid stenosis, but with no stroke or stroke-like symptoms during the previous 6 months.  In ACST-1 3000 patients were randomised between medical treatment only or medical treatment and ‘immediate’ surgery.  CEA involved a small (~3%) but definite peri-procedural risk of stroke or death, a substantial (~3% vs ~12%) reduction in the subsequent stroke rate over the next 5 years and hence a net reduction (~6% vs ~12%) in the overall 5-year risk of stroke or peri-procedural death.  The 5-year findings of ACST-1 are already changing surgical practice, and long-term follow-up of stroke rates continues7. 

Carotid artery stenting (CAS):  CAS is a newer method of treating carotid stenosis, usually via a distant artery, without carotid surgery. If the procedure starts from the groin then a catheter is passed from there up the femoral artery, up the aorta and then into the narrowed carotid artery, and a wire mesh stent is passed up the catheter and placed across the narrowed portion of the carotid artery. A balloon can then be inflated inside the stent to widen it and keep the artery open. The catheter and balloon are then removed.  During stent placement some of the diseased artery may crumble, blocking the blood supply to some large or small part of the brain and causing a major or minor stroke. Compared with CEA, CAS avoids surgical wound discomfort, is usually performed under local anaesthetic, could shorten hospital stay, might reduce the risk of peri-procedural heart attack or stroke and may be more acceptable to the patient than surgery. There is, however,  substantial uncertainty about the immediate hazards and long-term reliability of CAS, compared to CEA, when both are done by experienced doctors.

The need for a large-scale randomised trial comparing CEA vs CAS: A Cochrane meta-analysis of CEA vs CAS trials (mainly in symptomatic patients) stated that ‘the current evidence does not support a widespread change in clinical practice away from recommending CEA as the treatment of choice for suitable carotid artery stenosis. There is a strong case to continue recruitment in the current randomised trials comparing carotid stenting with [versus] endarterectomy’8.  Multicentre trials, undertaken mainly in symptomatic patients (eg, ICSS, SPACE, EVA-3S, CREST & SAPPHIRE9-13), have not yet resolved this uncertainty, and will probably be of limited size. Much larger trials are now needed, particularly in asymptomatic patients.  The European Stroke Initiative recommendations for stroke management supported this, and stated that ‘carotid angioplasty (balloon dilatation), with or without stenting, is not routinely recommended for patients with asymptomatic carotid stenosis. It may be considered in the context of randomised clinical trials’14.

Design and objectives

ACST-2 is a large, simple, randomised trial of CEA versus CAS for stroke prevention, and is designed to maximise recruitment by minimising each collaborator’s workload. It can be integrated easily into routine health care, as minimal information is required at randomisation and at the 1-month follow-up after the procedure (CEA or CAS). Annual follow-up will then be organised by the ACST office. The randomisation form and 1-month post-procedural form are the ONLY forms that routinely need completion by the doctor.  The trial will be international and will randomise patients with asymptomatic carotid artery stenosis in whom prompt physical intervention is thought to be needed, but where (even after magnetic resonance [MRA], computerised tomography [CTA] or some other type of angiography has shown both CEA and CAS to be anatomically practicable) there is still substantial uncertainty shared by patient and doctor about whether CEA or CAS is the more appropriate choice. Half of the patients will be randomised to CEA and half to CAS, then all are to be followed up for at least 5 years (mainly by post) and analysed on an intention-to-treat basis. Basing eligibility on uncertainty should ensure large-scale  recruitment of an appropriately heterogeneous group. This increases the medical value of the study, perhaps making it possible to determine whether the net effects of CEA/CAS are influenced by certain patient characteristics recorded at entry.

Primary objectives: To compare 1) peri-procedural risks (myocardial infarction [MI], stroke and death within the first month after the allocated CEA or CAS is attempted by an experienced practitioner), and 2) long-term (up to 5 or more years) prevention of stroke, particularly disabling or fatal stroke, in subsequent years.

Secondary objectives: Depending on numbers eventually randomised, the data may enable some types of patients to be identified in which one or other procedure is clearly preferable. As part of a health economic evaluation, procedural costs and stroke-related healthcare costs and quality of life will be assessed.

Starting at a centre: approving procedural Track Records

Local collaborators: Each centre must have a collaborating neurologist (or stroke physician), vascular surgeon and stenting interventionalist. They will be jointly responsible for patient recruitment, treatment and follow-up. The stenting interventionalist can be a radiologist, cardiologist, surgeon or physician with specialist training in carotid stenting. A ‘centre’ can be organised between colleagues in neighbouring hospitals, as long as locally practicable arrangements can be made to ensure that the information leaflet (Appendix 1) will be offered to many potentially eligible patients in good time for randomisation to be properly considered (ie, before one or the other procedure has already been effectively selected). For this, collaboration could be sought with all local centres that do carotid ultrasound, so that the trial information leaflet can be offered as soon as possible after stenosis has been found.

Approval of Track Records: Vascular surgeons who may perform CEA in the trial should already have had a reasonable amount of successful experience with the procedure. Likewise, interventionalists who may perform CAS in the trial should already have had a reasonable amount of experience with up-to-date techniques of stenting. Hence, before the trial is started at a centre, each collaborator who may perform trial procedures should send a ‘Track Record’ of their previous experience with CEA or CAS (as appropriate) to the ACST office (perhaps using the downloadable form on www.acst.org.uk). This record should be countersigned (as having been seen) by the local collaborating stroke physician or neurologist.  It will document details of the last 25, 50 or 100 procedures attempted (depending upon experience): range of dates when attempted (which, for CAS, should include at least 25 patients done using modern materials within the last few years); description of (and comments on any special reasons for) any technical failures; numbers of symptomatic and of asymptomatic patients; and, for both, number of strokes (fatal or non-fatal) and non-stroke deaths within 1 month of the procedure.

These records will be anonymised and then reviewed by the technical management committee. If there is not yet enough successful experience by the surgeon or by the stenting interventionalist at the centre then the start of the trial at that centre will be postponed until there is. In general (except for any cases where there were special reasons for technical failure), collaborators should have 8% stroke and death risk for symptomatic patients and 4% stroke and death risk for asymptomatic patients, as in previous major trials,3-6 or some appropriate combination of these percentages.

Ethical approval is required for each centre using this protocol, and the ACST office will help prospective collaborators with the process of obtaining this (to minimise the time taken). In parallel with this, a ‘Memorandum of intent’ to collaborate (a standard version of which is on page 23 and is also on the website) has to be signed at each centre, and  countersigned by the University of Oxford. Once this has been done, ethical approval has been obtained and both Track Records (for CEA and for CAS) approved centrally, eligible patients can be enrolled.

Identifying potentially eligible patients

Potential eligibility (and information leaflet)

•     Carotid artery stenosis detectable by duplex ultrasound, with no ipsilateral carotid territory symptoms
(or none for some months) and no previous procedure done on it, which might well need procedural treatment now with CEA or CAS. The information leaflet can be offered even before this is certain

•     Already started any appropriate medical treatment (eg, statin, aspirin etc), and already recovered from any necessary coronary procedures (eg, CABG)

•     Patient seems fit and willing for follow-up in person (at 1 month) and by annual letter (for at least 5 years)

Investigations show that both procedures (CEA and CAS) appear to be practicable and appropriate

•     Some type of angiography (eg, MRA or CTA) has already been done that has shown that CEA and CAS would both be anatomically practicable. The information leaflet can then be offered (or re-offered)

•     Doctor and (after information) patient both substantially uncertain about whether to treat with CEA or CAS, and the doctor sees no clear indication/contra-indication for either procedure

Contra-indications are specified not by the protocol but by the doctor, and might include:

•     Small likelihood of worthwhile benefit (eg, very low risk of stroke because stenosis is very minor, or major co-morbidity or life-threatening disease, such as advanced cancer)

•     Unsuitable for one or other procedure (eg, stenosis at carotid siphon that is inaccessible for CEA, or complex vasculature below the stenosis that would hinder CAS, or patient unfit for major surgery)

Offering information leaflet and consent form

•    As soon as possible after stenosis has been diagnosed, the possibility of joining the trial should be mentioned to the patient, who can then be given the information leaflet (Appendix 1) to consider. This can be done even before any angiography has been undertaken, when it is still not clear whether the patient will be eligible. Patients may wish to take the information leaflet away before deciding whether they are likely to join the study

•    The information leaflet can also be offered (or re-offered) later, without pressure. If the patient is found to be eligible and does decide to join, then written informed consent will be needed, and the patient should understand that they will be contacted annually by an ACST office (probably by post) for at least 5 years

•     When signing the consent section of the information leaflet, the patient will be asked to give contact details of the family doctor, and of 1 or 2 friends or relatives (with their agreement), any of whom could be contacted if the patient cannot be traced by the ACST office. (Patients who take the information leaflet away are asked to bring these contact details to the next clinic visit, to avoid delay, but clinic staff may still need to help get them completed)

Randomising by telephone

•    Complete at least part 1 of the randomisation form (Appendix 2) before telephoning to enter the patient, as these details are needed in the phone call. (The rest can be done later.)

•     Telephone the randomisation service on +44 (0)18 65 76 56 15. The randomising collaborator will be asked to confirm that the consent section of the information leaflet (with contact details) has already been signed, and to answer the questions on the first half of the randomisation notepad

•     The collaborator will then be given a unique 6-digit patient identification number and the treatment allocation to CEA or CAS. The patient is now in ACST-2. The ID number and allocation should be written onto the randomisation form and onto the foot of the consent form

•     Arrange for the allocated procedure (CEA or CAS) to be done as soon as possible (by a collaborator whose Track Record for that procedure has been approved), and send off completed randomisation & consent forms

•     Complete remainder of Randomisation Form and send, with signed Consent Form, to the study office

Treating (performing the allocated procedure)

•    The CEA or CAS should be done as soon as possible (ideally within the first month after randomisation) by a collaborator whose Track Record for that procedure has been approved. It is the responsibility of this collaborator to use techniques and equipment that are appropriate for routine clinical practice (eg, in Europe, CE-marked stents). Cerebral protection devices are optional (ie, at the collaborator’s discretion)

•     Before discharge

  • Schedule duplex ultrasound and a 1-month clinical follow-up visit
  • Schedule assessment by a neurologist/stroke physician (perhaps at a return visit within one month of the procedure) of whether or not the patient had a peri-procedural stroke or MI

•     All other care remains the responsibility of the patient’s doctor, and not the trial. Patients do not need to undergo any other tests or examinations beyond those provided as part of their routine care

1-month post-procedural follow-up

•    The 1-month post-procedural form (Appendix 3) should be completed and sent to the ACST office

•    If the 1-month post-procedural follow-up visit is missed, seek another appointment until contact is made (or the information is obtained otherwise). Even if the patient undergoes another procedure instead of the allocated procedure, the 1-month post-procedural form should still be completed

•    If it is decided that no procedure will be undertaken, please write to the trial office and explain why

Long-term annual follow-up (organised by the ACST office)

•    Patients will be contacted annually for at least 5 years by a letter originating from the international ACST office asking if they remain well, and  enclosing a brief questionnaire (Appendix 4). Both will be in the patient’s own language, with a prepaid envelope for return to an ACST office

•    If the patient replies that they have had a stroke, an appropriate doctor will be contacted to seek details of the stroke

•    If the patient does not reply, a similar letter (Appendix 5) will be sent to the family doctor, or to any friends or relatives whose contact details were given when the patient joined the study

•    If the patient is too disabled to complete the questionnaire, someone else (eg, the patient’s carer) can complete it with answers provided by the patient, or can complete it based on their own assessment of the patient

•    In the few cases where the patient and the contacts they gave do not provide the annual information, the local collaborator or country collaborator office may be asked to help trace the patient. UK patients will be flagged with the Office For National Statistics upon entry into the trial and, where available, national data repositories in other countries will likewise be used to facilitate data collection during the study

Although long-term follow-up will be organised by the ACST office, if a collaborator happens to know that a trial patient has had a stroke or has died, please write to the ACST office, describing if possible the nature and severity of the stroke or stating whether death was due to stroke.

Strokes and other major events

Strokes (within the first post-procedural month or during long-term postal follow-up)

Stroke outcome will be classified using the modified Rankin disability scale:

0  No symptoms at all from the stroke

1  No significant disability, despite any symptoms from the stroke: able to carry out usual activities

2  Slight disability because of the stroke: unable to carry out all previous activities but able to look after own affairs without assistance

3 Moderate disability from the stroke: requiring some help, but able to walk without assistance

4  Moderately severe disability from the stroke: unable to walk without assistance and unable to attend to own bodily needs without assistance

5  Severe disability from it: bedridden, incontinent and requiring constant nursing care and attention

6  Died directly or indirectly from the stroke

Peri- or post-procedural myocardial infarction (only within the first month)

It is necessary to report MI only if this occurs during the peri- or post-procedural (1 month) period. If more than one MI occurs in this month, each should be reported.  A definite diagnosis of MI can be made only if 2 of the following criteria are fulfilled:

1  Symptoms consistent with MI

2  Positive enzyme or biomarker (eg, troponin-T) changes consistent with MI

3  ECG changes consistent with MI

Death (within the first month, or later)

If the patient dies within one month of the trial procedure (CEA/CAS), the cause and circumstances should be described on the 1-month post-procedural form. Otherwise, follow-up will be by post from the ACST office, and the only information that is required on the death of a patient is the date of death and whether or not the cause of death was related to stroke. (This will, in general, be obtainable by the ACST office without any involvement of the local collaborators.)

Economic evaluation

The costs of the trial interventions and of any stroke-related impairment of quality of life will be evaluated, but this will not involve the local participating doctors. For all UK patients, direct access will be sought to the NHS electronic records of hospital activity. (These give, for each NHS hospital admission during the years of follow-up, the main reasons for the admission, the procedures undertaken, the duration of stay and the discharge diagnosis.) This allows NHS resource use during the entire follow-up period to be calculated, and the proportion attributed to stroke to be estimated. In addition, for all UK patients who have a peri-procedural MI or stroke (plus a matched sample of those who do not) a self-completion quality of life questionnaire (EuroQOL EQ-5D) will be sent directly from the trial office. Finally, every patient who has a stroke at any time during the study will be asked annually how it is affecting them.

Resource use during the treatment and follow-up periods will be estimated. The main components will be (a) the initial procedural costs; (b) further short-term re-treatment costs (ie, repeat or further procedures within a month); (c) the costs of any MIs within the first month and any stroke costs (both for strokes caused by the trial procedures and for those considered not to have been). The length of stay in hospital will be collected for these events. Annual follow-up questionnaires sent by the central trial office directly to the patient will collect data on the level of care currently required for a particular stroke patient (modified Rankin score), as well as information on how long the patient has had to have hospital or nursing home care for it. It will also seek information about strokes or carotid procedures after the first month. (Standard costs will be assumed for these procedures.) The economic analyses will evaluate the stroke-related quality of life at one month after the trial procedures as well as short and longer-term stroke outcome and costs.

Sample size, data analysis and safety monitoring

As the study is so easy, many hundreds of doctors and many thousands of patients can take part, and uniquely reliable evidence will then emerge comparing the immediate and the long-term safety of CEA and CAS. If a few thousand patients are randomised the results will be useful; if several thousand are randomised the results will be more useful; and if really large numbers are randomised then the results could affect the treatment of millions of patients in future decades.

The main outcomes will be MI, stroke or death 1 month after the allocated procedure (CEA or CAS), and long-term (up to 5 or more years) stroke rates. With 5000 randomised, a decrease of about 60% in the peri-procedural myocardial infarction rate with stenting versus surgery (eg, 2% CEA vs 0.8% CAS) and an increase of about 60% in the 5-year stroke rate (eg, 3% CEA vs 5% CAS) could both be detected at P<0.001 with 80% probability (ie, with 80% statistical power), or at 2P<0.05 with 95% power. The exact magnitude of any effect is currently not known, hence the need for the trial, but, taking into account existing information from other trials of CAS vs CEA, effects of this size might be realistic, meaningful and worthwhile.  Even smaller effects could be of substantial interest, but might require much larger numbers to be studied.

The results will be displayed using Kaplan-Meier graphs. Logrank analyses will compare stroke rates between those allocated CEA and those allocated CAS in specific time periods.  All patients should be followed up (unless they choose to withdraw from follow-up) whether the trial procedure is carried out or not, since the main trial analyses will be on an ‘intention-to-treat’ basis.  By the end of the recruitment period, data will be available to consider the peri-procedural outcomes, and with (by then) about 2 years follow-up on average, analyses will be possible of the early effects of CEA vs CAS on the annual incidence of various types of stroke, disabling stroke and fatal stroke.  Continued follow-up will allow more powerful analyses of these longer-term outcomes.

Subgroup analyses will be undertaken, where appropriate, to assess the relevance of prognostic factors.  In ACST-15, the 5-year risk of non-peri-procedural carotid territory ischaemic stroke was analysed in a number of categories, defined by: stroke severity; age; sex; pre-randomisation cholesterol; pre-randomisation blood pressure; ipsilateral and contralateral carotid artery diameter reduction – ie, degree of stenosis; plaque echolucency; ipsilateral and contralateral carotid territory status at entry; and diabetes and other problems, as recorded at entry.  Similar analyses are planned in ACST-2.

Data monitoring committee: During the study, interim analyses of major events will be supplied at least annually to an independent Data Monitoring Committee (DMC). The DMC will advise the Trial Steering Committee (TSC) whether there is an unacceptably high morbidity associated with CEA or CAS (either overall, or in particular centres, or in the centres with more limited prior experience), or if there is clear evidence that, for all patients or some particular types of patient, there is proof beyond reasonable doubt that one or the other procedure is preferable.  Until then, the TSC and collaborators will otherwise remain ignorant of interim results. 

Appropriate criteria of proof beyond reasonable doubt cannot be specified precisely, but a difference of at least 3 standard deviations in an interim analysis of a major endpoint may be needed to justify halting or modifying such a study prematurely. If this criterion were to be adopted, it would have the practical advantage that the exact number of interim analyses would be of little importance, so no fixed schedule is proposed.

At any point, anyone associated with the study may write through the ACST office to the DMC Chair drawing attention to any concerns they may have about the possibility of particular side-effects, or of particular categories of patient requiring special study, or indeed about any other matters thought relevant.

Patient withdrawal

A few of those who originally agreed to join the study may later change their minds and withdraw, but this should not materially affect the scientific integrity of the study. Some such patients may still be willing for information about their health to be collected according to the trial protocol but may prefer not to be contacted directly. Others may wish to withdraw entirely. In either case, if, after agreeing to join, the patient subsequently changes his or her mind, (s)he is free to do so without this adversely affecting his/her medical care.  Similarly, the patient’s doctor is free to give any other treatment that is considered to be in the patient’s best interest.

Trial organisation

The study will be managed on a day-to-day basis by the ACST office based at St George’s University of London.  All enquiries about the study should be directed to this office. Randomisation will be through the Clinical Trial Service Unit (CTSU), Oxford. Data will be stored on secure UK University computers, with identifiers held separately. The trial will be governed by a project management group that is responsible to the mainly independent Trial Steering Committee (TSC). A Technical Management Committee will be responsible for approving interventionalists/surgeons wishing to participate, after reviewing their procedural Track Records. An Endpoint Review Committee will classify strokes, and any other relevant outcomes. An Economic Evaluation Committee will guide the principal investigators on the UK and other health economic implications. Finally, the independent Data Monitoring Committee (DMC) will undertake interim analyses of trial data.

Funding

The UK National Institute of Health Research (NIHR) Health Technology Assessment programme has contributed towards the first 5 years of the trial and the BUPA Foundation, a UK medical research charity, is contributing towards at least the first 3 years. In addition the University of Oxford’s Clinical Trial Service Unit (CTSU) has provided some assistance free of charge. Doctors and patients who participate in the study are not paid to do so, and the final results will be freely available on the website and in journals.

Protocol modifications

This protocol, originally prepared by the ACST Office and CTSU, has been extensively reviewed and approved (MREC approval no. 05Q0201/66). It should not be modified unless this is essential. If any modification appears to be needed to comply with national or local regulations, it must be discussed in advance with the ACST office.

Publication

Results of the study will be prepared by a writing committee and circulated to all collaborators for comments prior to publication, Results will be published in the name of the ACST collaborative group.  The chief acknowledgement will be to the patients who participate in the study.

References

1.    Lopez AD, Mathers CD, Ezzati M, Jamison DT, Murray CJL (Eds). Global Burden of Disease & Risk Factors.
Oxford  University Press and The World Bank, Washington DC, 2006.

2.    Berry E, Kelly S, Westwood ME, Davies LM, Gough MJ et al. The cost-effectiveness of magnetic resonance angiography for carotid artery stenosis and peripheral vascular disease: a systematic review. Health Technology Assessment  2002; 6: no. 7.

3.    European Carotid Surgery Trialists’ Collaborative Group. MRC European Carotid Surgery Trial: interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis. Lancet 1991; 337: 1235-43.

4.    North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade stenosis. N Engl J Med 1991; 325: 445-53.

5.    MRC Asymptomatic Carotid Surgery Trial (ACST) Collaborative Group. Prevention of disabling and fatal strokes by successful carotid endarterectomy in patients without recent neurological symptoms: randomised controlled trial. Lancet 2004; 363: 1491-502.

6.    Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid stenosis. JAMA 1995; 273: 1421-28.

7.    Halliday A.  The Asymptomatic Carotid Surgery Trial has changed clinical practice. Pages 56-60 in: Vascular and Endovascular Controversies. Biba Publishing, 2006.

8.    Coward LJ, Featherstone RL, Brown MM. Percutaneous transluminal angioplasty and stenting for carotid artery stenosis (Cochrane Review). In: The Cochrane Library, Issue 3, 2004. Chichester, UK: Wiley & Sons.

9.    Featherstone RL, Brown MM, Coward LJ, on behalf of the ICSS Investigators. International Carotid Stenting Study: Protocol for a randomised clinical trial comparing carotid stenting with endarterectomy in symptomatic carotid artery stenosis. Cereb Dis 2004; 18: 69-74.

10.  The SPACE Collaborative Group. 30 day results from the SPACE trial of stent-protected angioplasty versus carotid endarterectomy in symptomatic patients: a randomised non-inferiority trial. Lancet 2006; 368: 1239-47

11.  Mas J-L, Chatellier G, Beyssen B, Branchereau A et al. Endarterectomy versus stenting in patients with symptomatic severe carotid stenosis N Engl J Med 2006; 355: 1660-71.

12.  Hobson RW. Carotid artery stenting. Surg Clin North Am 2004; 84: 1281-94.

13.  Yadav JS, Wholey MH, Kuntz RE, Fayad P, Katzen BT, Mishkel GJ, Bajwa TK, et al. Protected carotid-artery stenting versus endarterectomy in high-risk patients. N Engl J Med 2004; 351: 1493-501.

14.  The European Stroke Initiative Executive Committee and Writing Committee. European Stroke Initiative recommendations for stroke management - update 2003. Cereb Dis 2003; 16: 311-37. 

Appendix 1 to 4 – Trial forms: see separate pdf files.