The purpose of this study is to determine whether Sodium Fluoride imaging (using Positron Emission Tomography-Computed Tomography - PET-CT) is able to predict disease progression in acute aortic syndrome.

Acute Aortic Syndrome encompasses multiple aortopathies, including aortic dissection, intramural haematoma and penetrating aortic ulcers. Acute aortic syndrome has a three year mortality approaching 25%. To date, other than the initial aortic diameter, there are no accurate methods of establishing the risk of disease progression in patients with acute aortic syndrome.

In vascular disease, microcalcification occurs in response to necrotic inflammation. Using computed tomography and positron emission tomography (PET-CT), early microcalcification can be identified using uptake of the radiotracer 18F-sodium fluoride. This can identify high risk-lesions in the aorta, coronary and carotid arteries, and appears to be indicative of necrotic and heavily inflamed tissue. In abdominal aortic aneurysms, 18F-sodium fluoride binding predicts aortic expansion and the risk of aneurysm rupture or requirement for surgical repair.

The study investigators, therefore, propose to evaluate the ability of 18F-sodium fluoride to identify regions of necrotic inflammation in acute aortic syndrome to predict aortic expansion and disease progression.

Control patients with a normal calibre aorta will be recruited from the National Abdominal Aortic Aneurysm Screening Programme and Vascular Out-Patient Clinics. Patients with acute aortic syndrome and chronic aortic disease will undergo clinical assessments and 18F Sodium Fluoride PET/CT scans at baseline and 12-months. Clinical follow-up will continue for up to 3 years from recruitment.

INCLUSION CRITERIA:

Patients with Acute Aortic Syndrome or Chronic Aortic Disease:

• A diagnosis of acute aortic syndrome as defined as per the European Society of Cardiology guidelines on the management of aortic disease a compatible clinical presentation with CT or magnetic resonance imaging confirming acute aortic syndrome.
• Adults over the age of 25 years
• Participants who have had previous open or thoracic endovascular aortic repair (TEVAR) are eligible to participate in the study.

Healthy Controls:

• No previous diagnosis of aortic disease
• Over the age of 55 years

EXCLUSION CRITERIA:

• The inability of patients to undergo PET/CT scanning
• Chronic kidney disease (eGFR ≤ 30 mL/min/1.73 m2)
• Major or untreated cancer
• Pregnancy
• Allergy or contra-indication to iodinated contrast
• Inability or unwillingness to give informed consent

Participants with acute aortic syndrome will be recruited from emergency hospital admissions. Participants with chronic aortic disease will be recruited from out-patient clinics and thoracic aortic surveillance programmes. Healthy volunteers will be recruited from the national abdominal aortic aneurysm screening service and vascular out-patient department clinics.

Individual participant data will not be shared outside the current research group