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Review of Vascular Services
Key Messages from the Literature
(Arterial inpatient procedures)
Author: Dr P Stevenson
Date: 25 January 2012
Version: 1
Publication/ Distribution:

Project Board

North Wales Clinicians
Review Date: Ongoing
Purpose and Summary of Document:
This working draft document has been prepared to support BCUHB in its
review of vascular services. It considers:
Background to the current situation;
Key aspects of safety, quality, and sustainability by which proposed service
model options generated by the review can be assessed;
Guidance and recommendations made by national bodies and authorities.
Work Plan reference: N/A
Public Health Wales
1.
Review of vascular services key messages
from the Literature
Introduction
This paper supports the review of Vascular Services in North Wales. It is
one of a number of reviews undertaken by BCUHB, including a review of
emergency general surgical services.
Currently vascular surgery is a subspecialty of general surgery, though
plans are well advanced to secure vascular surgery as a speciality in its
own right.
In addition to the move towards specialty status for vascular surgery,
there are a number of other drivers for undertaking a separate and
specific review of vascular services, namely:

The introduction in 2012 of a Abdominal Aortic Aneurysm screening
programme for men aged 65;

The need to provide optimum quality care including emergency care
for all vascular surgery;

To enable and inform workforce planning;

To meet the training requirements that are likely to be mandatory
for training locations;

The meet the European Working Time Directive;

To enable workable model(s) of delivery consistent with
recommendations from the other major reviews, particularly
emergency surgery.

To consider the optimal provision of interventional radiology,
specialist anaesthesia and support staff as an integral part of
vascular services.
1.1 Aim of Review
The key strategic question is, “How should vascular services be configured
for North Wales to ensure a sustainable service that addresses national
and local strategic policies and drivers?”
The remit of the review is:
From a population perspective, to:

Review the needs of North Wales residents for vascular services;
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
To review the existing service profile, consider relevant
literature/evidence for models of provision that address safety,
quality and sustainability in the short and long term;

To recommend a future service configuration to the BCU Board.
This review of the literature focuses on the second of these aims, and
specifically to consider relevant evidence for models of provision which are
safe and of high quality. The focus of this report is arterial inpatient
procedures.
1.2 Background
The Vascular Society of Great Britain and Ireland has recently produced a
document on the Provision of Services for Patients with Vascular disease.1
The main thrust of the document is to recommend an overall model of
service provision, and in addition there are recommendations and
statements regarding particular patient groups and procedures, eg carotid
artery intervention.
In summary the model is:
Either a network, or a single fully centralised site but in either case all
elective and emergency arterial intervention to happen on a single site,
thus developing a high volume arterial hospital providing the following:

A 24/7 on-site vascular on call rota for vascular emergencies of 1:6
or greater, covered by vascular surgeons and interventional
radiologists;

A 24/7 critical care facility;

A minimum number of AAA procedures (100 over three years);

Audit mortality and aim for 3.5% elective AAA mortality;

An onsite vascular laboratory;

Dedicated wards and at least one endovascular theatre.
Whether a centralised service or a network, a range of services (excluding
arterial surgery) would be provided in the non-arterial hospitals.
The rationale for this model is the assertion of strong volume outcome
data emerging with particularly good evidence for aortic aneurysm
surgery2, but also for other procedures including carotid endarterectomy3
and aorto-bifemoral bypass4.
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It is also asserted that specialist vascular teams involving surgeons,
interventional radiologists and anaesthetists achieve superior clinical
outcomes.5,6
A further key issue in rural areas are access times. Paras 6.21 and 6.22 of
the Vascular Society document1 assert that patient survival after a
ruptured aneurysm is much higher following arrival in a non-vascular
hospital if the patient is then transferred to the vascular service, and this
advantage persists even with up to 4 hours of hypotension. (unless a
cardiac arrest)
Patients diagnosed with a vascular condition requiring emergency
intervention should be diagnosed and referred within one hour of arrival
and the transfer time should also be less than one hour. In other words
the target time for arrival at spoke hospital to vascular unit is under 2
hours.
There are therefore three key questions, for which the evidence base
needs to be examined in detail, namely:

The evidence for high volume/better outcome;

The evidence for combined teams/better outcome;

The evidence for survivable transfer times to a vascular unit for
definitive assessment and treatment.
1.3 Methods
In view of the short time scales available to produce a summary report of
the evidence, a method drawn from an approach known as rapid appraisal
was used.
The key steps included:

A rapid scope and scan of the literature – key NHS/International
evidence sources (eg NICE, Royal Colleges, Cochrane Reviews and
Health Technology Assessments, NCEPOD reports);

A more detailed search carried out by the Library, Knowledge
Management service of Public Health Wales focussed on the three
questions above;

Identification of a group of key clinicians with expertise in vascular
services, including vascular surgeons, interventional radiologists,
and specialist anaesthetists. (an expert stakeholder group);
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
Key evidence sources discussed with the stakeholder group and
other sources of intelligence identified;

Triangulation to the check the reliability of information gathered;

Feedback of collated findings to the stakeholder group and the
project board to allow checking of drafts and correct
misinterpretations.
This pragmatic approach allows for ongoing review and updating as
further evidence becomes available.
2.
The Evidence
In assessing the evidence of models of vascular care it is imperative to
assess which model(s) of service provision provides the safest outcomes
for patients, specifically the lowest possible operative mortality following
vascular procedures. In addition services should be provided to minimise
other adverse outcomes such as stroke and limb amputation.
The review is in large part driven by the need to respond to screen
detected aneurysms in the new aortic aneurysm screening programme
(although AAA work is but a part of the wide range of vascular
interventions now possible).
In the AAA programme men, who believing themselves to be well are
screened, and then invited to surgery. The only way this can be ethically
acceptable is to ensure that the surgery offered gives the lowest possible
mortality rates which can be achieved with optimal modern techniques,
equipment and training.
2.1 Evidence regarding Volume/Outcome
There are numerous studies looking at the relationship between volume
and outcome for vascular surgical procedures. Three key reports
highlighted below attempt to synthesize the evidence for AAA repair (The
first also looks at CE). The first paper reviews studies which are now
somewhat historical, but it is included as it was a major and thorough
review at the time. All three reports refer to open surgical repair rather
than endovascular procedures which have become more common in recent
years.
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Report 1
A Health Technology Assessment published in 20007 reviewed 36 papers
published between 1986 and 1998 looking at the relationship between
volume and outcome. A recurring theme is the need to minimise bias in
volume-outcome studies, so that account is taken of any other factors
other than volume that are likely to affect patient outcomes.
Of the 36 studies identified in the search, 17 were concerned with carotid
endarterectomy, 16 concerned AAA repair, and four were concerned with
other vascular interventions.
When taken together, the CE studies were supportive of a positive
volume-outcome relationship existing at the physician level for both
mortality and stroke, but the weight of evidence was less conclusive when
consideration was restricted to those studies which made a full adjustment
for case-mix. Indeed there was no clear support either way.
For unruptured AAAs, the evidence supported the existence of a positive
volume-outcome relationship at both hospital and physician level. For
ruptured aneurysms the weight of evidence was against there being a
positive volume relationship at the hospital level, while for physicians
there was no clear support either way.
For “other vascular interventions” there were insufficient studies to draw
conclusions.
The authors of the report acknowledge that all but two of the studies
considered were based on retrospective data. They point out that the
ideal would be randomised trials, but these would be difficult to undertake
in this context, so the best pragmatic option may be detailed prospective
cohort studies with full adjustment for case-mix.
Report 2
A US study published in 2002 looked at the variation in death rate after
aortic abdominal aneurysmectomy in the United States.8
Patients
undergoing repair of intact or ruptured AAAs in the Nationwide Inpatient
Sample for 1996 and 1997 were included in the study (n=13,887). This
was a 20% stratified random sample representative of all US hospitals.
Unadjusted and case mix adjusted analyses were performed.
For repair of intact AAAs, high volume hospitals had a lower death rate
than lower volume hospitals. The death rate after repair of ruptured AAA
was also slightly lower at high volume hospitals. In a multi-variate
analysis adjusting for case-mix, having surgery at a low volume hospital
was associated with a 56% increased risk of in-hospital death.
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Report 3
A study published in 2007 analysed all of the published literature on the
volume-outcome relationship in AAA surgery, using meta-analysis and
systematic review.9 They also analysed HES data for 2000. This review
considered the volume-outcome relationship only at the institutional level,
not at the physician level.
For elective aneurysm repair, after exclusions 32 articles and the HES data
provided information on volume of elective AAA repair and mortality. The
mean mortality rate was 9.5% and the observed mortality rate fell as the
operative volume increased. Most articles showed a statistically significant
reduction in mortality with increasing volume.
For ruptured aneurysms, the mortality rate across all studies was 37.1%.
Analysis unequivocally favoured surgery at higher volume hospitals.
The authors made reference to the importance of minimising bias in
volume-outcome studies and the role of case-mix.
They state that
although some older studies employed no case-mix adjustment, more
recent articles commonly employed the Romano modification of the
Charlson co-morbidity score. They were not specific in the paper as to
which studies had used adjustment.
They state that studies specifically investigating the role of case-mix found
no impact on the observed volume-outcome relationships when using
adjusted or unadjusted data. They also infer that despite referral bias of
high-risk patients to tertiary hospitals, higher-volume hospitals have a
lower actual and risk-adjusted in–hospital death rate.
Holt also quotes evidence to show that for AAA hospital volume and
surgeon volume are independent predictors of mortality with an additive
effect, and that higher volume vascular surgeons operating in higher
volume hospitals achieve the lowest mortality rates.
2.1.1 Other Studies looking at Volume/Outcome
Holt et al published a further study looking at the relationship between
hospital volume and outcome after AAA surgery in the UK from 2000 to
2005.10
They concluded that elective AAA repair undertaken at high-volume
hospitals showed volume related improvements in mortality. They
asserted that the critical threshold was 32 elective AAA repairs per year.
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This conclusion has been challenged by Troeng11, who pointed out that in
the five hospital volume groups Holt looked at, the mortality rate in the
intermediate groups was stable and comparable statistically to the highest
volume group. His own analysis of contemporary (within last ten years)
papers looking at volume and mortality for elective AAA surgery leads him
to conclude that 10-15 procedures annually in at a single site may be
sufficient to secure safe open repair.
However, scrutiny of the Holt paper10 does show that in the highest
volume quintile the death rate is 5.9%, compared to 7.7%, 7.2%, and
7.6% in the next three groups by volume in descending order of
magnitude. This seems an important difference when we are considering
elective surgery (in the future including screen detected). As it is based
on all cases over a five year period in the UK, statistical testing is really
redundant – we need only eyeball the data.
It is also not clear how Troeng reached his conclusions – in scrutinizing
one study of HES data from 1997-200212, he states that the average
mortality of 7.7% was reached in centres performing only 14 elective
repairs or more. However, 7.7% cannot now be regarded as acceptable
for elective repair, and certainly not for screen detected aneurysm.
Holt et al also carried out a meta-analysis and systematic review of the
relationship between hospital volume and outcome following carotid
endarterectomy.13
Twenty-five articles were analysed. Overall, the pooled effect estimate
was odds ratio 0.78 in favour of surgery at higher volume units, with a
critical volume threshold of 79 CEA per annum.
The key factors underlying this relationship between volume and outcome
related to hospital infrastructure. For CEA, lower volume surgeons
achieved results similar to higher volume surgeons when operating in
higher volume hospitals, supporting the concept that hospital
infrastructure was a major component of the volume-outcome
relationship. However, death and stroke rate for CEA are lowest for highvolume vascular specialist surgeons operating in a high volume hospital.
A paper looking at surgeon volume and operative mortality in the USA
across a range of procedures found that for elective AAA repair, the
operative mortality among patients treated by low-volume surgeons at
high-volume hospitals was higher than the overall operative mortality at
low-volume hospitals. Best results, ie lowest operative mortality were
again achieved by high volume surgeons in high volume hospitals14.
Some papers have looked at other procedures – for example Dimick et al
looked at hospital-volume related differences in aorto-bifemoral bypass
operative mortality in the United States.15 The AFB operative mortality
was significantly lower at high-volume hospitals.
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Awopetu et al conducted a systematic review and meta-analysis of the
relationship between hospital volume and outcome for lower limb arterial
surgery16. The systematic review included 452,093 patients form 10
studies, and five studies were included in meta-analyses. They concluded
that higher-volume hospitals were associated with reduced amputation
and mortality rates after lower limb vascular surgery, with OR of 0.81 for
mortality and OR of O.88 for amputation in favour of higher volume
hospitals.
2.1.2 Conclusion
Studies on the volume-mortality relationship for vascular surgical
procedures have a number of methodological problems. Studies use
different definitions of high and low volume, variable groupings by volume
or volume as a continuous variable. Adjustment for case-mix or riskadjustment and referrals is also problematic and variable. Studies often
look at retrospective data – there are no randomised trials. Most studies
use in-hospital death rates, but for some comparisons 30 day mortality
may be a better outcome to use. Many studies are from the USA, and the
conclusions of such trials may not be completely applicable to UK practice.
Nevertheless the accumulated weight of evidence taken as a whole is in
favour of higher volume hospitals for arterial surgery.
Although it is clear that units doing very low numbers of procedures do
not generally produce good results, it is more difficult though to give a
precise figure as to thresholds for a minimum number of procedures per
hospital per annum.
“Reasonable” results may be obtained from say 15 procedures/per
unit/per annum, but Holt does provide persuasive evidence that a
threshold around 30 cases per annum gives optimal results10, and the aim
must surely be to achieve optimal results, not “reasonable”.
With regard to the provision of a model of service for the repair of screen
detected aortic aneurysm it is difficult to disagree with the conclusions of
the National Screening Committee below:
Before a screening programme could be set up, the local NHS would need to agree a
suitable network of screening and vascular units…….the vascular units providing
treatment for AAA would need to agree to conform to the clinical and service
standards agreed for UK wide implementation,. These standards will incorporate the
requirements put forward by the VSGBI for the treatment of AAA.
The evidence is not so clear cut for emergency repair. Holt points out that
there was no reduction in mortality rate with increasing annual volume for
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analysis9. The data for the meta-analysis came from the USA where travel
times may be longer than a UK average.
Patients reaching hospital in the USA may have been a selected group who
had a contained rupture and sufficient physiological reserve to survive the
transfer. Of course travel times in North Wale can also be lengthy, this
issue will be considered further later. (see section 2.3)
There is a significant body of evidence in favour of higher volume units for
other procedures such as carotid endarterectomy.
In addition to higher volume hospitals with the advantages of a better
infrastructure, optimal outcomes are most likely to occur with high volume
surgeons operating within those hospitals.
2.1.3 National Standards
The NCEPOD report of 200517 on AAA stated that there was little to
support surgeons continuing to treat single figure numbers of elective
cases on a regular annual basis.
It also recommended that clinicians, purchasers, Trusts and Strategic
Health Authorities should review whether elective aortic aneurysm surgery
should be concentrated in fewer hospitals.
2.2 Evidence
working
and
recommendations
regarding
team
In 2002 the RCR produced guidance on the provision of vascular radiology
services.18
This document supports the recommendation of the NCEPOD 2000 report,
which stated that vascular radiologists and surgeons should work as a
team both in the decision as to what procedures to undertake and in the
management of any complications.
With the development of both vascular surgical and radiological services,
the RCR document noted the significant development of team working,
with many elective and emergency vascular procedures managed jointly
by surgeons and vascular radiologists, that often worked effectively during
the normal working day, but out of hours is often less effective and less
efficient. The RCR recommended that vascular radiologists and surgeons
should attend regular joint meetings, at which all vascular cases could be
discussed.
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In a draft report, The Provision of Emergency Vascular Services 2007, the
RCR recommends under models for emergency vascular services that
vascular units should include both radiological and surgical expertise.
The same report also highlights that colleagues in anaesthesia and
intensive care are vital members of the multidisciplinary team.
Another RCR report, Standards for providing a 24 hour interventional
radiology service, published in 2008 recommends that out of hours
provision must be subject to a formal rota, stating that it is not
sustainable, safe or timely to rely on ad hoc methods of trying to find a
suitable radiologist who is not officially on call.
The NCEPOD report17 on ruptured AAA showed a 30 day mortality of 27%
for anaesthetists who undertook a higher than median volume of
aneurysm repairs, compared to 40% for those who took a lower than
median volume.
NCEPOD have recommended that anaesthetic
departments should reduce the number of anaesthetists caring for very
small numbers of elective and emergency aortic surgery care.
Another paper, a retrospective cohort study, identified patients undergoing
major vascular surgery (lower limb revascularisation, elective and
ruptured AAA, endovascular aneurysm repair and carotid endarterectomy)
over a five year period 2003-719. For the overall cohort, care from
vascular anaesthetists was independently associated with reduced 30-day
and medium–term mortality. For elective patients vascular anaesthesia
was associated with reduced 2 year mortality though not 30 day mortality,
and for emergency surgery no effect was shown. Some of the negative
findings could be due to under-powering of the study.
Clearly more work and analysis is needed in the areas of specialist
vascular anaesthesia, but it is likely there could be some benefits, and
certainly for elective AAA work on screen detected aneurysm there could
be a case for securing anaesthetists with reasonable experience of
vascular work as an adjunct to driving down post-operative mortality rates
to the lowest possible.
There was complete consensus of our North Wales expert stakeholder
group that vascular surgery and interventional radiology should work
closely together, fitting the recommendations of the RCR.
With regards to anaesthetics, the evidence supports those with greater
experience of vascular procedures giving better outcomes – there will be
some problems in achieving this on rotas, but the aspiration should be
that any anaesthetist providing anaesthesia for vascular procedures at
least has reasonable experience of that type of work.
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Further issues include the necessity for other staff to be available at all
time wherever arterial surgery is provided, for example nursing staff and
radiographers.
A RCR/RCN document20 advises that departments of
clinical radiology carrying out interventional procedures should have and
adequate number of appropriately registered nurses to provide effective
in-hours and out of hours cover.
Departments with a large interventional radiology workload should have
sufficient wte registered radiology nurses to provide at least one in five on
call rota.
2.2.1 Issues regarding treatment of AAA
There are two techniques available to treat unruptured aneurysms.,
conventional open surgery repair (OSR) and endovascular aneurysm
repair (EVAR). EVAR is a minimally invasive procedure commonly done by
interventional radiologists in collaboration with a vascular surgeon21. EVAR
has become a more common intervention in recent years.
Two randomised studies in the UK, the EVAR122 and EVAR223 trials have
investigated the outcomes of AAAs treated electively by EVAR. The EVAR1
trial compared the outcome of EVAR against OSR in patients who were
suitable for OSR and had suitable morphology for the stent-graft (around
50% of patients).
The EVAR1 trial showed a near three-fold reduction in 30 day mortality
with the use of EVAR when compared to OSR. The EVAR2 trial indicated
that for patients unsuitable for OSR there was no overall benefit in those
treated with EVAR compared with no intervention.
There may be some benefit of EVAR over OSR in treating ruptured AAA,
but without randomised data it is unclear whether this is due to real
benefit, publication bias or case selection21.
What does seem clear though that in case selection and collaborative
working, and using the developing evidence to guide decision making, it is
essential that vascular surgeons and interventional radiology work closely
together in determining and carrying out optimal treatment for each and
every patient.
Of course the increased use of EVAR has lead to the same questions being
asked regarding volume and outcome as for open repair. A recent study
aimed to quantify the relationship between the volume and outcome from
elective endovascular or open repair of AAAs in England between 2005
and 200724.
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This study had many of the same limitations as previous work, but the
authors concluded that EVAR did demonstrate an independent volume
effect, that total aneurysm experience (open and endovascular) appeared
to be important in determining outcome, and that the uptake of EVAR in
England is insufficient contributing to operative deaths.
There is a further complicating factor to be considered. The EVAR trial
investigators have recently reported25 that although EVAR is associated
with significantly lower operative mortality than open repair, no
differences were seen in total mortality or aneurysm related mortality in
the long term. The rates converged at 2 years for any cause mortality,
and 6 years for aneurysm related mortality. EVAR was associated with
increased rates of graft-related complications and re-interventions and
was more costly.
This clearly has implications for case selection for EVAR, patient choice,
ongoing surveillance after repair and cost-effectiveness.
2.3 Evidence regarding Travel Times
It is sometimes argued that North Wales has unique geographical and
travel problems but as recent report pointed out this is not the case26.
There are similar travel times in Scotland, West Wales, Cumbria and many
rural communities.
For patients requiring elective vascular surgery the question of travel
times may be felt to be less important – that if a higher quality and safer
service is best delivered from a higher volume single unit then the
accessing such a service is worth the additional travel and inconvenience
incurred.
Interestingly a study in Sheffield27 using a mailed questionnaire found that
patients who responded had a preference for local treatment to the extent
they were willing to incur increased risks of perioperative mortality and
amputation to receive treatment at their local hospital. However, it must
be debatable how ethical it would be to implement a less safe service even
with informed patient/public opinion.
It is for emergency vascular problems that the real issue of access times
arises. Such problems include acutely ischaemic limbs and vascular
trauma, but leaking AAAs are perhaps the major area of debate.
For patients with a ruptured AAA there is good evidence that patient
outcomes are not related to the distance travelled if they reach a centre
where vascular expertise is available28.
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This study in a sparsely populated region of Scotland found that the death
rate from ruptured AAA was almost identical for those living more than or
less than 50 miles away from the operating hospital in Inverness. The
overall mortality from ruptured AAA and the operative mortality rates in
this rural area, where a significant proportion of the patients live more
than 25 miles away from the main hospital, were similar to those in urban
areas reported in the literature.
Another study in West Sussex29 failed to find any association between
travel time and survival after ruptured AAA, though the travel times were
short, with a mean potential travel time to nearest hospital 14.2 minutes.
Many studies have suggested lower mortality for those who had to travel
further to get to the hospital carrying out the operative intervention. This
is likely to be due to selection bias, as they do not include those who died
in the community or pre-operatively29.
The diagnosis of acute limb ischaemia is usually obvious in the
community, and the onset of permanent damage is delayed for several
hours, so there is a window of opportunity for safe transfer30.
3.
Overall Conclusions
Despite a range of methodological weaknesses, the evidence as a whole
tends to support the view that better outcomes result from delivering open
arterial surgery, particularly elective AAA procedures and CE, in higher
volume units. The evidence is perhaps less persuasive with regard to
ruptured AAA.
It is difficult to be precise regarding exactly what higher volume means,
but certainly with regard to AAA elective surgery, although there is some
evidence that units performing around 15 procedures per annum may
produce reasonable outcomes the aim must be to aspire to a model which
produces optimum outcomes.
This is even more necessary when
developing services for screen detected aneurysm. A strong case can be
made for the recommendation in the VSGBI paper namely 100 procedures
over 3 years and it would seem that this standard will in any case be
mandatory for screen detected aneurysm.
However, a recent editorial31, from the St George’s Vascular Institute
(same authors as many of the often quoted papers on volume/outcome)
takes a very measured view on the setting of threshold volumes for safety
in arterial surgery.
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They state – “...the use of these data determine a discrete threshold
numbers of cases at which optimal outcomes are obtained is debatable.
Most studies use historical data based on primarily on open aneurysm
repair; any consideration of threshold volumes for implementation by
health care providers should take into account the improvements in
outcome seen with endovascular aneurysm repair (EVAR)”
They also point out that studies attempting to define a threshold have
heterogeneous results, and that more recent studies including EVAR have
found that mortality continues to improve as operative caseload increases.
They further conclude that both ruptured AAA and urgent AAA repair were
associated with a lower mortality in hospitals performing a greater number
of elective OAR and EVAR. This relationship was again continuous rather
than dichotomous.
In the United Kingdom, improvements in outcome at high-volume centres
of excellence are also conferred by nonsurgical factors such as specialist
anaesthetists and intensive care in addition to increase uptake of EVAR24.
The editorial31 concludes that the quality of vascular surgery cannot be
studied or improved by solely reporting volume-dependent outcomes such
as mortality, but that there must also be a focus on process and structure.
Deficiencies in process include the lack of a specialist vascular and
endovascular training programme for surgeons32.
A further paper33 summarises the volume-outcome relationships in
vascular surgery. Once again the main message is that increased volumes
are likely to give improved outcomes. For some procedures at least eg
elective OAR, incremental improvement may be more modest at very high
volumes.
There is strong clinical support in North Wales for multi-disciplinary
working, and there is evidence from the literature as well as standards
from professional bodies which provide further support.
A population needs assessment, and analysis of current service provision
put alongside this evidence review will further inform optimal best quality
model(s) of service provision for North Wales.
Any proposed model will have to take account not only of the evidence
around volume and outcome, but be safe and of high quality, ensure
reasonable access times, workable rotas in line with EWTD, enable joint
working and rotas between vascular surgery, interventional radiology and
preferably anaesthetics, meet the training requirements of the Royal
Colleges, provide the necessary infrastructure, be able to recruit to
consultant posts following retirements, be compatible with the general
needs and requirements of emergency and trauma surgery, and be costeffective and affordable.
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Importantly consultation and involvement of the local population is also
needed.
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3.1 Summary of Key Messages

Practice within vascular services is changing and developing rapidly,
for example greater use of EVAR for aneurysm repair. This means
the evidence base is constantly evolving.
However, balanced judgements on service provision need to be
made now on the current best available evidence.

Overall the available evidence indicates that higher volume units and
operators are associated with lower mortality, but the methodology
for most studies is weak and often analyses have used data which is
now more than a decade old, and which predates the introduction of
new
practices/techniques
notably
EVAR.
However
the
volume/outcome relationship still holds in the latest studies.

It is not possible to set an absolute threshold for safe practice with
regard to case numbers for vascular procedures.
It seems indisputable that very low numbers of particular vascular
procedures (eg AAA repair) per unit per annum do give a worse
outcome (mortality).
In general mortality rates decrease continuously with increased
volume, though for some procedures at least the incremental
decrease may be much less at higher volumes.

Structure and process are important. Teams should be
multidisciplinary, and include vascular surgeons, interventional
radiologists, specialist anaesthetists and support staff. Facilities
need to be high quality and comprehensive. Both the team and the
facilities need to be available 24/7, with proper rotas for out of
hours cover.

There is no evidence that increased travel time increase mortality
for ruptured AAA. This catastrophic event will be unsurvivable for
many patients no matter how close operative facilities are. Travel
times may need further consideration within the broader category of
trauma involving vascular damage, for example road traffic
accidents and limb threatening disease.

Overall the evidence from the literature would support a move to a
fewer number of units performing vascular procedures in North
Wales. This would facilitate efficient provision of high quality,
modern comprehensive facilities, workable staffing and rotas,
reasonable volumes of activity, compliance with national guidance,
optimal treatment for screen detected AAA, and compliance with
likely future training requirements.
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Abbreviations
AAA
Aortic Abdominal Aneurysm
AFB
Aorto-femoral bypass
CEA
Carotid endarterectomy
EVAR
Endovascular aneurysm repair
EWTD
European working time directive
OSR
Open surgical repair
RCR
Royal College of Radiologists
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