port to improve the regional quality of carotid imaging over two years. It has also involved the local delivery of four study days to support practica

Transcription

1 Meeting standards in the carotid imaging pathway can we achieve the vision? RAD Magazine, 38, 440, by Borsha Sarker Lead clinical specialist (vascular ultrasound), Gateshead Health NHS Foundation Trust, Queen Elizabeth Hospital Stroke is the third leading cause of death and the leading cause of severe disability. The National Audit Office 1 published a report in 2005 identifying that stroke care was poor, patchy and fragmented, with inefficient use of resources and a low priority within the NHS. This report was the main driver for the National Stroke Strategy (NSS) 2 that was launched in 2007, setting actions and progress measures to achieve its vision over 10 years. This was supplemented by the Imaging Guide for the NSS 3 and followed by guidance from the National Institute for Clinical Excellence (NICE) 4 in July To implement the NSS, England was divided into 28 stroke networks, including my own North of England CardioVascular Network (NECVN). This was in turn supported by the NHS Stroke Improvement Program (SIP) in December This posed the challenge for patients with transient ischaemic attack of symptom to surgery within 48 hours.. H H G Eastcott performed the first carotid endarterectomy (CEA) in 1954, 5 thereby being the first to show that an operation could prevent a stroke. This involved removing the plaque and part of the vessel wall causing a stenosis in the internal carotid artery. From current National Audit Office statistics, there are approximately 110,000 strokes and 20,000 transient ischaemic attacks a year in England alone. I became interested in carotid ultrasound as a student in 1990 and watched my first carotid endarterectomy in 1992, performed by Averil Mansfield (since President of the Vascular Surgical Society and Chairwoman of the Stroke Association) who succeeded Eastcott. I was lucky to meet the then-retired Felix Eastcott 6 (nicknamed after the cartoon cat) who still came along to our early morning multidisciplinary team meetings at St Mary s Hospital, London, and gaining his wealth of experience, history and interesting anecdotes. Multicentre trials later followed to validate his findings in symptomatic patients and have continued to be conducted and re-analysed, the two largest and most significant being the North American (NASCET) 7,9 and European (ECST) 8 trials. In 1992, based on a BMJ article about the importance of imaging to identify patients with >70% stenosis, I responded by carrying out an early survey of radiology departments. This was to investigate the capacity of imaging departments to respond to the need for non-invasive carotid imaging with Doppler ultrasound, sampled across five regions. 10 I was then based at St Mary s Hospital academic surgical unit under Professor Andrew Nicolaides, who was responsible for much of the early research around imaging for carotid stenosis Now 20 years later, it seems we are examining our capacity again and I have found myself reviewing the same issues at our local stroke network meetings. However, since then we have been issued with some major national guidance documents to help. 2-4 I first learnt to use the Blackshear and Strandness criteria from Seattle to diagnose and calculate internal carotid stenosis, divided into five categories (A, B, C, D and D+). These were developed in the 1980s when the degree of stenosis to gain surgical benefit in symptomatic patients had not then been defined. When this was set at 70%, 7,9 it became important to define this more precisely using ultrasound. 11,12 The so-called St Mary s Ratio was then being used and developed at my workplace to calculate stenosis within the internal carotid artery. Therefore it was easier to understand the original research behind it, how it had been derived and some of the pitfalls when using it. 11,12 Crucially, it could determine the 70% cut-off, but also stratify stenosis in bands, both above and below this level. It is difficult to choose just one duplex criterion to calculate ICA stenosis, from the multiplicity of validated criteria available. Using two or three can leave the operator more confident when there is a match across various methods. However, it can also cause the dilemma of a variety of results to rationalise against other imaging modalities at the MDTM. This can lead one to rely on that unvalidated tool, the eyeball of the experienced operator! Provided any disease is not too calcified, power Doppler can help greatly here as the image, when appropriately adjusted with good use of low scale and high dynamic range, provides a close anatomical match to MRA reconstructed images. This enables images from both modalities to be compared on an equivalent basis, despite the sometimes variable quantitative calculations from each modality, both of which suffer from varying degrees of intra- and inter-observer variability (figure 1). As plaque ulceration has a strong correlation with embolic symptoms, this has become increasingly as important as the degree of stenosis. The nature of the plaque and its morphology has generated much research, 13 especially in relation to embolic symptoms. Soft or predominantly anechoic/echolucent plaques are regarded as more associated with embolic symptoms. Power Doppler also helps greatly in defining the normal calibre distal vessel required for effective surgery and demonstrating any plaque surface ulceration, although recent developments in multidetector CT angiography (MDCTA) have shown its has a superior sensitivity in detecting plaque ulceration 14 (figure 2). Since 1997, I have also been using area reduction measurements in cross section (a calculation available using Philips equipment, but as yet unvalidated to my knowledge). Interestingly, in my own practice, I have found a very good correlation against the percentage stenosis using St Mary s Ratio and good intra- and inter-observer variability (figure 3). In 2008, to overcome the clinical governance problems experienced by operators using differing diagnostic criteria that caused wide variations across the country, a joint working party from the Vascular Surgical Society and Society for Vascular Technology published a paper giving recommendations for reporting of carotid ultrasound. 15 This paper was also endorsed by most relevant UK representative bodies. The adoption of this guidance, however, was not initially universal. The uptake anecdotally has been increasing, but some of the barriers within my own region were identified as training and support issues. In April 2010, a partnership project from Newcastle was given an award from the Strategic Health Authority (SHA) Workforce Development Innovation Fund (WDIF) to improve quality and productivity. This was a web-based programme of education and sup-

2 port to improve the regional quality of carotid imaging over two years. It has also involved the local delivery of four study days to support practical skills and quality standards embedded within the Joint Recommendations, for staff already trained in carotid ultrasound. It does not seek to replace the training element from university for staff new to the technique. To summarise, the main points in the UK reporting recommendations for carotid ultrasound are: a, calculations and results should refer to the NASCET method b, four key velocities to be measured and recorded in the ICA and CCA at standardised points c, All velocities to be measured at an angle between 45 and 60 degrees d, Three key calculations to grade the ICA stenosis (PSV, PSVR and St Mary s ratio to stratify in decile bands) e, Record the presence or otherwise of a clear distal lumen f, Note other factors, eg diagnostic reliability, plaque type, atypical anatomy etc. Since then, these have been locally incorporated into the Minimum Core Standards for Stroke and TIA care, created by the North of England Cardiovascular Network (NECVN). 16 These were completed in October 2010 and take a combination of standards from the NSS, 2 the imaging guide 3 and NICE guidance 4 as well as the joint recommendations. 15 This combined document was created using local working parties from May 2008 until its local publication to debate the differences in the published documents, reaching a consensus view and a pragmatic approach to implementation. It has been used on an operational level to compare performance across the region, to guide local policy and for the commissioning of services. The core standards have also been used to improve quality, eg by MDTM attendance, to influence managers and as funding leverage locally. In practice these new reporting recommendations have lengthened the time taken to write our reports. We now have to type the velocities onto the report and the criteria and calculations have been in some cases unfamiliar initially. We have been reluctant to completely dispense with our previous methods, so now compare the new against the old and still there is not always universal agreement with the new criteria. I have included a couple of recent conflicting examples, both >90% (figures 4 and 5). We have noticed some mismatch at the lower degrees of stenosis using the decile banding of the St Mary s ratio in the 50-60% range (placing them at <50%, when previously we would have calculated 50-60%) and I would be interested to find if this is the case elsewhere. At least however, there is now some national standardisation. So what has all this meant for us at shop floor level? I work in a medium-sized DGH, now a Foundation Trust. We see carotids per week with no GP access. Prior to 2006 we rarely scanned carotids as in-patients and most were given the next routine appointment. In Gateshead, this has always been well within six weeks for many years prior to the advent of the 18-week target. However, we are lucky to have ten sessions a week solely dedicated to vascular ultrasound provision. From being investigated, discussed and treated if surgery was required, the timescales for carotids slowly reduced to within six weeks. With the advent of the NSS and NICE guidance they have decreased to two weeks and we now have an aspirational local NECVN target of 48 hours for high-risk patients. This has only been achieved locally in a tiny percentage of cases. Weekly meetings have been crucial to improving timely treatment. We are not a large unit and getting the stroke physicians, radiology staff and surgeons together at the MDTM has facilitated a faster pathway. We implemented ring-fenced daily appointments linked to the daily rapid access TIA clinics for high risk TIAs based on the ABCD 2 score two years ago. Acute in-patients now have access within 24 hours from Monday to Friday. All low risk patients (ABCD 2 score <4) are offered an appointment within a week. The sonographers try to attend at least 50% of weekly MDTMs in rotation, and despite our small unit, we rarely have an inquorate meeting. However, it is still not enough. Targets have been marching ahead of us and one cannot rest on the last standard achieved for long. The first step from primary care through to assessment and first investigation is fast due to FAST (face, arm, speech test) excuse the pun. However, there are still unacceptable delays between referral and surgical treatment (when required) due to several factors, including priority access to the MR scanner. This is forcing us look at a second carotid duplex instead of MRA that we have used as our second modality so far, prior to surgery. However, this can erode ongoing access to other modalities, due to deskilling, and enforce dependence on ultrasound. The other key standard to be achieved by January 2012 locally is weekend carotid imaging. The NSS suggests that ideally all three imaging modalities should be available 24/7. This meets the immediate hurdle of resources, especially in the current financial climate. Skills are also in short supply. Sonographers and MR radiographers when staffing the weekend for a small number of potential cases are then unavailable for the bulk of work, with a wider case mix in the week. The jam is being spread too thinly! Then there is the issue of how far to extend the training. How many carotid ultrasound scans does one need to perform annually to remain competent and how frequently? Does the unit have the number of cases to support the number of staff and to concentrate the numbers into a training session? Larger units have managed to staff weekend sessions and maintain skills due to a larger patient base, but the move towards centralisation is not popular with patients. Locally, when offered faster care further from home, patients have declined and opted to wait. This has brought us to look at alternative solutions. One is a networked solution for smaller units, pooling their patient group and the hyper-acute stroke services they already provide. CTA has become more universally available and our CT is already staffed 24/7. The latest software and technology has marched ahead of the published advice from the DoH in The latest multi-detector CT angiograms are comparable with the gold standard contrast enhanced MRA (CEMRA), but there is still the obstacle of reporting the scans and the impact on workload and training. Also, slightly contentiously, from an imaging point of view the timescales for the implementation of the local stroke network standards appear to have diverged somewhat when considering the provision of weekend care. The local NECVN standard for imaging now demands plans in place by Jan 2012 for an imaging diagnosis within 24 hours of symptoms at the weekend. However, the target for rapid surgery still remains unchanged (within two weeks of symptoms), rather than reducing to match the challenging out-of-hours demands being made on imaging on Saturdays and Sundays. Perhaps those units that have a daily decision-making team may offer the best hope for a way forward. They combine imaging modalities, stroke physician, radiologist and surgeon and a daily virtual MDTM discussion by phone or in person. It is easy to be overwhelmed with the pace of change in this area and disheartened with delays in progress, lack of funding and support. However, we all form part of our ageing population and it is in our own interests to make this work. So much has already changed and, as a colleague pointed out just this week, our targets are much more demanding than the cancer targets, with everything to be completed within 48 hours. Yet, until now stroke and TIA has been given a much lower priority, but has a massive potential cost saving to the public purse. The direct costs in were at least three billion pounds, with a wider economic cost of eight billion pounds annually. 17 Care for people who have had a stroke has significantly improved since the NAO report of 2005 and implementa-

3 tion of the NSS in However, 300,000 people are living with moderate to severe disabilities as a result of stroke. Without preventative action, there is likely to be an increase in strokes as the population ages. 17 So can we achieve the vision of the National Stroke Strategy? I hope I ve given a flavour of our approach to it at Gateshead. Its aim was to achieve the improvements over 10 years. We have still got time, but a long way to go. Thanks to Dr T Cassidy, Mr C P Oates and Miss E Morris for their help and advice. References 1, Department of Health. Reducing brain damage: Faster access to better stroke care. National Audit Office 16 November , Department of Health. National Stroke Strategy. December , Department of Health. Implementing the National Stroke Strategy an imaging guide. June , National Institute for Health and Clinical Excellence. Clinical guidelines stroke: The diagnosis and acute management of stroke and transient ischaemic attacks. July , Eastcott H H G, Pinching G W, Rob C G. Reconstruction of the internal carotid artery in a patient with intermittent attacks of hemiplegia. The Lancet 1954;2: , Felix Eastcott: A eulogy. Mansfield A. Ann R Coll Engl (Suppl) 2010;92. 7, Barnett H J, Taylor D W, Eliasziw M et al. Benefit of carotid endarterectomy in patients with symptomatic, moderate or severe stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators. The New England Journal of Medicine 1998;339(20): , Randomised trial of endarterectomy for recently symptomatic carotid stenosis: final results of the MRC European Carotid Surgery Trial (ECST). The Lancet 1998;351(9113): , Ferguson C G, Eliasziw M, Barr H W et al. The North American Symptomatic Carotid Endarterectomy Trial: Surgical results in 1415 patients. Stroke 1999;30(9) , Sarker A B. Carotid Duplex do we need to know? British Medical Ultrasound Society Annual Scientific Meeting December , Dhanjil S, Jameel M, Nicolaides A et al. Ratio of peak systolic velocity of internal carotid to end diastolic of common carotid; new duplex criteria for grading internal carotid stenosis. J Vasc Technol 1997;21: , Nicolaides A N, Shifrin E G, Bradbury A, Dhanjil S et al. Angiographic and duplex grading of internal carotid stenosis; can we overcome the confusion? J Endovasc Surg 1996;3: , U-King-Im J M, Tang T, Moustafa R R et al. Imaging the cellular biology of the carotid plaque. Int J of Stroke 2007; , Saba L, Caddeo G, Sanfilippo R et al. CT and ultrasound in the study of ulcerated carotid plaque compared with surgical results; potentialities and advantages of multidetector row CT angiography. AJNR 2007;28: , Oates C P et al. Joint recommendations for reporting carotid ultrasound investigations in the United Kingdom. Eur J Vasc Endovasc Surg (2008). 16, North of England Cardiovascular Network (2010). Minimum core standards for the diagnosis and treatment of suspected TIA patients. 17, Department of Health. Progress in improving stroke care. National Audit Office 3 February FIGURE 1 Minimal ICA disease and 99% ICA stenosis. A B FIGURE 2A and 2B Ulcerated plaque within a 60-70% stenosis, using reduced scale colour Doppler (A), again delineated better with high dynamic range and low scale power Doppler (B), also showing the normal caliber distal ICA lumen.

4 FIGURE 3 Example intraobserver variability transverse sections for a 60-70% left ICA stenosis. FIGURES 4 and 5 Two visually very similar high grade lesions from patients recently going for carotid surgery. A C B D FIGURE 4a-4d 90% stenosis by area loss (A), but not supported by usual velocity criteria (B), which are barely abnormal at 158cm/s PSV and 41cm EDV. Ulcerated plaque within same stenosis, using colour Doppler (C), appreciated beautifully with power Doppler (D). Confirmed by second duplex (contrast contraindicated due to renal function).

5 A B C D E FIGURE 5a-5e 92% left ICA stenosis shown with power Doppler (A), with high grade velocities (528cm/s PSV and 186cm EDV (B), by area loss (C), confirmed by axial MDCTA (D), and 3D volume rendered reformat (E).