Elective AAA Repair

What is elective infra-renal abdominal aortic aneurysm repair?

An abdominal aortic aneurysm (AAA) is the local expansion of the abdominal aorta, a large artery that takes blood from the heart to the abdomen and lower parts of the body. It is a condition that tends not to produce symptoms until it ruptures. An aneurysm can rupture without warning, causing the sudden collapse or death of the patient. Most abdominal aortic aneurysms occur below the kidneys (i.e., are infra-renal).

A ruptured AAA requires emergency surgery. Screening and intervening to treat larger AAAs reduces the risk of rupture, and the National Abdominal Aortic Aneurysm Screening Programme (NAAASP) was introduced in 2010 to identify and treat at risk aneurysms prior to rupture. Once detected, treatment to repair the AAA before it ruptures can be planned with the patient, and surgery is typically performed as an elective procedure.

Aneurysms may be treated by either open surgery, or by an endovascular repair (EVAR). In open surgery, the AAA is repaired through an incision in the abdomen. An EVAR procedure involves the insertion of a stent graft through the groin. Both are major operations. The risk of death after elective AAA surgery is roughly 4% for open surgery and 1% following endovascular repair. The decision on whether EVAR is preferred over an open repair is made jointly by the patient and the clinical team, taking into account characteristics of the aneurysm, patient age, and fitness.

What information is being published on AAA repair?

The results for AAA repair are broken down into three procedure types – elective infra-renal, ruptured and elective complex. The term complex is used to describe those aneurysms that occur above the level of the renal (kidney) arteries.

For each trust, and for each type of AAA repair, we present the number of procedures they submitted to the NVR in the reporting period. The colour and symbol next to this number indicate the case ascertainment, which is the number of procedures the trust submitted compared to the total they carried out according to national data sources.

The average number of days between assessment and procedure is shown in the second row. The numbers in brackets are the typical number of days a patient will have to wait. This period covers an important component of the referral process that is under the direct control of vascular services. The National AAA Screening Programme has emphasised the importance of the timely scheduling of an elective repair to mitigate the risk of a patient’s AAA rupturing while waiting for treatment. This is a small absolute risk of rupture, but the NAAASP recommends a target of 8 weeks from date of referral from the NAAASP to the date of the repair.

We also publish the average length of stay for patients undergoing an elective infra-renal AAA repair. The numbers in brackets are the typical range that patients will stay in hospital (the typical range is the shortest and longest lengths of stay of the middle 50% of patients. The results for a particular trust can be seen in relation to the overall national length of stay. The length of stay is split into open and endovascular repairs at a trust level only because most consultants do not undertake sufficient numbers of either procedure to produce reliable outcome figures for them individually.

These pages give information on the proportion of patients who were discharged from hospital alive after surgery for those patients who had an elective repair of an infra-renal abdominal aortic aneurysm.

The information on this website for all aortic procedures was updated in November 2018.

Which consultants have their outcomes for elective infra-renal AAA repair published?

These webpages contain information on consultant vascular surgeons and interventional radiologists who are currently undertaking elective AAA repair in English NHS hospitals and who submitted data to the National Vascular Registry. It also contains information on consultants working in Scotland, Wales and Northern Ireland who have consented to have their figures published.

The webpages do not contain the results of any consultant who:

  • was known to have retired from the NHS
  • is active within the NHS but has informed us that he/she is no longer performing these procedures.

Many consultants now perform AAA surgery in pairs, operating together. We are not able to reflect this in this analysis. Cases are reported against the consultant with primary responsibility for the care of the patient.

Why are the figures for some consultants not included?

We have included the names of consultants with five or fewer cases but show their results as an asterisk (*). This is to prevent individual patients from being identified and is in line with guidance on protecting patient confidentiality from the Office for National Statistics.

There are various reasons why consultants may have few procedures in the database. First, they may have only been appointed as a consultant during the last year or two. We have indicated this situation with a symbol “A” beside their name. Their results are only shown as an asterisk (*) if they have fewer than 20 cases in the NVR.

Second, some consultants with a practice that specialises in the treatment of complex AAA may have small numbers of infra-renal AAA repairs. Consultant level information is not available for complex or emergency AAA repairs. Finally, some consultants may have lower numbers than expected because data on some patients were not submitted to the NVR or because the submitted data were incomplete.

What data is being used to produce this outcome information?

The time period for each AAA repair metric is shown next to the metric. The difference is because the results for some types of AAA is not available before 2014 due to changes in the NVR datasets. Also, some procedures are more common than others, and showing results over a small time period may not have a sufficient number to produce reliable outcome figures.

How are the data analysed?

The in-hospital survival rate is calculated by identifying all patients who were discharged from hospital alive after an elective AAA repair and dividing this number by all patients operated on by that particular consultant or at that NHS trust.

The results have been risk adjusted for patient case-mix to ensure that consultants and NHS trusts that take on more difficult cases are not unfairly penalised. The reason for producing risk-adjusted outcomes is because the characteristics of patients treated by consultants and NHS trusts will vary, and the outcome of care will be influenced by these characteristics – on average, outcomes are often worse for sicker patients. Risk adjustment allows us to take account of these factors.
For outcomes after elective AAA repair, we used a risk model that contained the patient factors: age at surgery, sex, AAA diameter, white cell count, serum sodium, serum creatinine, cardiac disease, ASA grade.