Defining Personalised Management Strategies in Patients with Abdominal Aortic Aneurysms

The aorta is the major blood vessel that pumps blood from the heart to the rest of the body. The part of aorta in the belly is called the abdominal aorta, and should be ~20mm in diameter. An abdominal aortic aneurysm (AAA) is an abnormal ballooning of this section to >30mm. AAA mostly affects men in the retirement age (>65 years old), but women are also at risk. Cigarette smoking and genetics are two of the main factors known to cause AAAs. Left untreated, AAA slowly expands and eventually bursts - this results in sudden onset of severe belly pain and internal bleeding. Only 25% of patients will survive a burst AAA - each year about 6,000 people in the UK and 20,000 people worldwide die from burst AAAs.

People with AAAs don't notice symptoms until it bursts. Fortunately, AAAs can be easily detected with an ultrasound scan. In 2009, the NHS established a national AAA screening program (NAAASP) for men over the age of 65. Since the program started, thousands of new AAA patients are diagnosed by the NAAASP each year. In addition, similar numbers of AAAs are detected by chance from scans done for other medical reasons.

There are two types of surgery to treat AAAs: traditional open surgery involves a big cut in the belly to directly repair the AAA and replace it with a synthetic fabric tube; newer "keyhole" surgery involves tiny cuts in the groin to put in stents that cover the AAA from inside.

International guidelines recommend that patients with small AAAs (between 30 to 54mm in diameter) should be monitored by regular ultrasound scans, and for surgery to be considered when an AAA grows larger than 55mm. In combination, these have been shown to decrease the chance of people dying from burst AAAs. To make sure people undergo surgery before the AAA bursts, the NHS spends millions each year to monitor them. This cost will continue to rise as more patients are being monitored. The global market of aneurysm stents is also expanding rapidly (>£3bn by 2024) as more and more stents are being used to treat patients. Alarmingly, many more aortic stent procedures are being done in fee-for-service health care systems (such as Germany and USA) before the AAA reaches the diameter of 55mm.

I recently engaged hundreds of AAA patients at Oxford to see what is most important to them in terms of AAA management. 'Frequency of AAA monitoring' emerged as one of the most important issues during AAA monitoring. I also conducted an online international survey of vascular surgeons, where 'new ways to predict AAA growth' was voted as the top priority for aneurysm research. Such a method did not exist, and would be hugely valuable to the patients and the NHS: It will help clinicians decide how often each patient needs monitoring scans; It will also safeguard patients against unnecessary surgery.

I have developed a method for the prediction of AAA growth with good accuracy. This method involves an additional blood test taken at the same time at the routine AAA monitoring scan. I am also developing a method to predict AAA growth by the analysis of computerised tomography scans.

This proposed project has the primary aim to validate my method of AAA growth prediction. I will assess the accuracy of my prediction method using patient samples collected at different hospitals, internationally. In addition, I will improve the prediction method by doing further analyses on blood samples and CT scans to find additional markers that can be useful. Lastly, I will develop a point of care testing kit (to measure blood) and a medical software (to analyse CT images). These will make our prediction methods accessible to clinical practice.