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 3% for open surgery and 0.5% 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.

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.

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 2021.

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 NHS trust.

The results have been risk adjusted for patient case-mix to ensure that 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 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: sex, AAA diameter, cardiac disease, renal disease and national COVID-19 admission rates.