The UK’s National Institute for Health and Care Excellence (NICE) has issued draft guidance on abdominal aortic aneurysm (AAA) diagnosis and management. The most notable recommendation within the guideline is related to repairing unruptured aneurysms where the guideline states that patients should not be offered endovascular repair (EVAR) if open surgical repair is suitable.
This latest draft guideline issued in May is for consultation and will update NICE technology appraisal guidance 167 which was published in February 2009. According to NICE, the guideline aims to improve care by helping people who are at risk to get tested, specifying how often to monitor asymptomatic aneurysms, and identifying when aneurysm repair is needed and which procedure will work best.
On monitoring the risk of rupture, NICE recommends that patients with an asymptomatic AAA be offered surveillance with aortic ultrasound every three months if the AAA is 4.5–5.4cm or every two years if the AAA is 3–4.4cm.
When it comes to repairing unruptured aneurysms, the guideline suggests that physicians should consider aneurysm repair for people with an unruptured AAA if it is symptomatic, asymptomatic and 5.5cm or larger, or asymptomatic, larger than 4cm and has grown by more than 1cm in one year. But add that patients meeting these criteria should be offered surgical repair unless there are anaesthetic or medical contraindications.
As for EVAR for repairing unruptured aneurysms, the instructions in the draft guideline are clear: “Do not offer endovascular repair (EVAR) to people with an unruptured infrarenal AAA if open surgical repair is suitable. Do not offer EVAR to people with an unruptured infrarenal AAA if open surgical repair is unsuitable because of their anaesthetic and medical condition. Do not offer complex EVAR to people with an unruptured AAA if open surgical repair is a suitable option, except as part of a randomised controlled trial comparing complex EVAR with open surgical repair. Do not offer complex EVAR to an unruptured AAA if open surgical repair is unsuitable because of their anaesthetic and medical condition,” they state.
In an effort to explain how NICE comes to these recommendations, the rationale within the document indicates that there is “no evidence that EVAR for people with an unruptured infrarenal AAA provides long-term benefit compared with open surgical repair. While EVAR is associated with fewer perioperative deaths, it has more long-term complications, and these complications mean that people will need further procedures. There is some evidence that EVAR is associated with worse long-term survival than open surgical repair. EVAR also has higher net costs than open surgical repair. The evidence shows that, even if long-term benefits were achievable, they could not plausibly be sufficient to outweigh these costs. Open surgical repair is unsuitable for some people with an unruptured AAA because of their anaesthetic risk and/or medical comorbidities. For these people, the risks of their AAA rupturing, if no repair is attempted, have to be balanced against the perioperative risks and long-term complications associated with EVAR. The evidence shows that the average person receiving EVAR has an uncertain chance of a small net benefit, compared with the large and certain increase in costs. Therefore, the committee agreed that elective EVAR cannot be considered an effective use of NHS resources in this population.”
Additionally, the NICE committee found that the evidence for complex EVAR was limited in quantity and quality. However, they note that complex EVAR grafts are much more expensive than standard devices, so the difference in cost between EVAR and open surgical repair is even greater than in infrarenal AAAs. The committee also noted that the instructions for use of the grafts that are currently available do not cover complex AAAs. “Although there is currently no evidence that complex EVAR has better outcomes than open surgical repair, people with complex AAAs have higher perioperative mortality rates. Because of this, a perioperative survival benefit equivalent to that seen with EVAR for infrarenal AAAs could potentially be more influential in complex AAAs. Therefore, the committee agreed that more information would be helpful, so it recommended that the use of complex EVAR should be restricted to randomised trials.”
According to the guideline document, the committee also discussed complex EVAR for patients for whom open surgical repair is not a suitable option because of their anaesthetic risk and/or medical co-morbidities. They agreed that, in this population, people who need complex EVAR could not plausibly have better outcomes than those who need standard infrarenal EVAR. As they had not recommended standard EVAR in this population, the committee agreed that they could not recommend complex EVAR either. Further, the committee did not recommend using complex EVAR in randomised trials in these circumstances, because it would be unethical to randomise people to a treatment with a high risk of perioperative death when there is no prospect of long-term benefits at reasonable cost.
“For each of these recommendations, the committee considered whether there were any specific groups that would benefit from standard or complex EVAR for unruptured AAAs. They explored groups defined by age, sex, AAA diameter and life expectancy, but there were no groups in which the benefits would outweigh the harm and costs,” the guideline states.
The guideline committee acknowledges that the recommendations on EVAR will have a large impact on practice, as EVAR is a widely performed procedure. “EVAR is currently used more frequently than open surgical repair in some areas, so a diverse group of people both within and outside the national screening programme will need to update their knowledge,” they state. On a more positive outlook, the committee believes that the recommendations will “minimise harm by reducing long-term mortality and the need for reintervention as a result of problems with EVAR. Reductions in EVAR use and subsequent EVAR-related reinterventions will lead to cost savings within the NHS”.
EVAR did not lose out all round, as the NICE draft guideline does allow for the consideration of EVAR for the repair of ruptured aneurysms, at least of the infrarenal kind. The guideline suggests that either EVAR or open surgical repair should be considered for repair of a ruptured infrarenal AAA. They advise that EVAR provides more benefit than open surgical repair for most people, especially for women and for men over the age of 70 years, and open surgical repair is likely to provide a better balance of benefits and harms in men under the age of 70 years.
However, for ruptured complex AAA the guideline instructs that open surgical repair should be considered, but that complex EVAR should not be offered to people with a ruptured AAA if open surgical repair is suitable, except as part of a randomised controlled trial comparing complex EVAR with open surgical repair.
According to the document’s rationale, the evidence considered by the committee showed that, compared with open surgical repair, a strategy that uses EVAR (where anatomically possible) to repair ruptured infrarenal AAAs provides a reasonable balance of benefits and costs. Further, as the average cost-effectiveness results for EVAR were favourable, the committee discussed whether they should recommend EVAR whenever it is possible. They decided not to, for two reasons: “Firstly, there is uncertainty in the evidence for EVAR. People who had EVAR for a ruptured AAA were followed up for at most seven years. People who had EVAR for an unruptured AAA were followed up for 15 years, and the committee noted that these data suggested that EVAR may be worse than open surgical repair in the long run. There are some signs that a similar long-term pattern may develop in trials of ruptured AAA, so it is possible that longer-term data would show EVAR to be worse than open surgical repair for people with ruptured AAA as well.
“Secondly, there was evidence that the balance of benefits and costs of EVAR varies between different groups of people with ruptured AAA. In particular, women clearly have better short-term survival after EVAR, whereas the evidence favours open surgical repair for younger men. Therefore, the committee recommended that either EVAR or open repair can be considered, and provided detail on the groups for which each approach is likely to be best.
“Complex EVAR is only recommended within the context of a randomised controlled trial because there is currently no evidence to support it as an option for people with ruptured complex AAA.”
As for how the recommendations might affect practice, NICE maintains that they will have little impact on current practice, “as both standard EVAR and open surgery are currently offered to people with ruptured infrarenal AAA. In relation to complex EVAR, the recommendation not to use it outside of randomised trials will limit the use of a technically complex and expensive procedure in people for whom open surgery is a safe and suitable option”.
When EVAR is used, the draft guideline suggests that patients should be monitored for complications, and that they should be enrolled into a surveillance imaging programme and the frequency of surveillance imaging should be based on the patient’s risk of graft-related complications. It recommends the use of contrast-enhanced CT angiography to detect postoperative complications and further aneurysm expansion.
Finally, the draft AAA guidelines make some key recommendations for research. Firstly, it encourages research into monitoring frequencies and repair thresholds, noting that more frequent monitoring increases the chances of identifying aneurysms that have grown large enough to need repair. “It is important to establish how often aneurysms should be monitored to keep the risk of rupture as low as possible while making the best use of NHS resources,” they state.
Secondly, the document calls for research into the effectiveness of endovascular aneurysm repair and open surgical repair of unruptured and ruptured abdominal aortic aneurysms, noting that while EVAR is a widely performed non-invasive alternative to open surgical repair, it is more expensive. “Although EVAR has been shown to produce no long-term benefit over open surgical repair in people with unruptured infrarenal aneurysms, it is less clear whether this is the same in people with unruptured or ruptured juxtarenal, suprarenal type IV, and short-necked infrarenal aneurysms. As a result, research is needed to identify how effective complex EVAR is in these populations”.
The committee also recommended research into macrolides for slowing aneurysm growth and reducing risk of rupture, metformin for slowing aneurysm growth and reducing the risk of rupture, tranexamic acid for preventing and treating excessive blood loss during EVAR or open surgical repair and preoperative exercise programmes for improving the outcome of aneurysm repair. Other recommendations for research include the use of direct oral anticoagulants after AAA repair, transfer to specialist vascular units, permissive hypotension, and surveillance after EVAR.
Finally, on surveillance after EVAR, the guideline suggests research should be conducted to determine the risks, benefits and cost implications of different surveillance protocols in patients who have undergone EVAR, as well as which device and patient-related variables can be used in a risk model to inform amendments to surveillance frequencies and modalities. Such research is already underway in the form of prognostic modelling, based on data from the EVAR trials and validated by a contemporary EVAR dataset from Helsinki, Finland.
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