The purpose of this trial is to assess whether a strategy of endovascular repair (if aortic morphology is suitable, open repair if not) versus open repair reduces early mortality for patients with suspected ruptured abdominal aortic aneurysm (AAA).

Rupture of the main blood vessel of the body in the abdomen (ruptured abdominal aortic aneurysm) is fatal in over three-quarters of cases. In the past, those that survive have reached hospital alive and undergone emergency open surgery to repair the aneurysm and stop the bleeding: however, after this major emergency surgery only half the patients leave hospital alive. A newer, less-invasive method of aneurysm repair, endovascular repair, is based on repairing the aneurysm by inserting the repair graft up through one of the arteries in the groin. Endovascular repair has been tested in the elective situation and is associated with a 3-fold reduction in operative mortality versus the standard open surgery. Early work with selected patients has suggested that endovascular repair may be associated with up to a 2-fold reduction in operative mortality and more rapid recovery for ruptured abdominal aortic aneurysms. However, only 55-70% patients are anatomically suitable for endovascular repair.

Therefore, this research aims to determine whether a strategy of preferential emergency endovascular repair reduces both the mortality and cost of ruptured abdominal aortic aneurysm.

Critically ill patients with a clinical diagnosis of ruptured aneurysm will be randomised, in the emergency room, to a strategy of endovascular repair if possible (endovascular first) or to current standard care (immediate transfer to the operating theatre for emergency open surgery). Patients randomised to "endovascular first" will require a specialist radiological examination (computed tomography, CT scan) to assess anatomical suitability and plan for endovascular repair. This will cause a short delay before definitive repair can be commenced. Those patients not suitable for endovascular repair, after CT scan, will be taken for standard open surgery. Patients will be randomised at 16-20 specialist centres in the United Kingdom (UK), who have already attained sufficient experience in using endovascular repair for ruptured aneurysms and can offer a routine service.

The primary outcome measure is 30-day operative mortality, which we hope will improve by 14% with the "endovascular first" strategy (from 47% to 33%). Secondary outcome measures include 24h, in-hospital and 1-year and 3-year mortality, re-interventions associated with the two treatment strategies as well as quality of life, costs and cost-effectiveness.

The research team includes specialists in clinical trials, health economics, statistics, pre-hospital & emergency care, interventional radiology, vascular & endovascular surgery, critical care, aneurysm research and a service user.

Inclusion Criteria:

• Clinical suspicion of ruptured abdominal aortic aneurysm after review in Accident and Emergency (or other hospital unit).
• Men and women over the age of 50 years will be recruited.

Exclusion Criteria:

• Patients with known connective tissue disorders (eg Marfan syndrome) where endovascular repair may not be beneficial.
• Patients with known previous repair of an abdominal aortic aneurysm, because procedures either open or endovascular are likely to be very complex and there are no guidelines for anatomical restriction to repair.
• Deeply unconscious and moribund patients since the chances of recovery are minimal.

The datasets generated during and/or analysed during the current study are/will be available upon request from mjs212@medschl.cam.ac.uk after approval by the Trial Management Committee.

The data will become available in December 2017 and for the subsequent 3 years.