Abstract 2021: 18 F-Sodium Fluoride Positron Emission Tomography To Assess Thoracic Aortopathy In Bicuspid Aortic Valve Disease

Background: Bicuspid aortic valve is associated with thoracic aortopathy with many patients suffering aortic dissection below the aortic diameter threshold for prophylactic aortic replacement surgery. In aortopathy, the aortic wall media initially undergoes increasing microcalcification due to elastin fibre fragmentation but with disease progression, elastin fibre degradation leads to loss of aortic microcalcification. 18 F-Sodium fluoride positron emission tomography (PET) is a non-invasive method of detecting arterial microcalcification that has been successfully used in cardiovascular disease risk stratification. Aims: To determine if aortic 18 F-sodium fluoride imaging can identify aortopathy and predict subsequent disease progression in patients with bicuspid aortic valve disease. Methods: In this prospective cohort study, 77 patients with bicuspid aortic valve from clinical sites across Scotland and 18 healthy volunteers, underwent 18 F-sodium fluoride PET-computed tomography (PET-CT) followed immediately by PET-magnetic resonance imaging (PET-MRI). Maximum standardised uptake values (SUVmax) were determined in the ascending aorta. Aortic diameters were measured in aortic axial CINE MRI sequences. Patients were followed-up at 24 months with a further PET-MRI. Annualised change in aortic size index (mm/m 2 /year) and annualised change in SUVmax stratified in tertiles were calculated. Results: Patients with bicuspid aortic valve disease had higher SUVmax than control subjects, especially in those with aortic dilatation. Baseline SUVmax was associated with annualised aortic expansion rate independent of baseline aortic size (β=0.45, p=0.001). Patients in tertile 1 (loss of SUVmax over time) exhibited greater aortic growth (0.60±0.50 mm/m 2 /year) than those with stable SUVmax (tertile 2, 0.26±0.36 mm/m 2 /year) or increasing SUVmax (tertile 3, 0.24±0.36 mm/m 2 /year; p=0.01). Conclusion: Aortic microcalcification activity is increased in aortopathy of patients with bicuspid aortic valve. Loss of aortic microcalcification is associated with more rapid disease progression and represents a promising new approach to the identification of patients at higher risk of aortic complications.