18F-Sodium Fluoride Positron Emission Tomography and Computed Tomography in Acute Aortic Syndrome.

BACKGROUND: Acute aortic syndrome is associated with aortic medial degeneration. 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) detects microscopic tissue calcification as a marker of disease activity. OBJECTIVES: In a proof-of-concept study, this investigation aimed to establish whether 18F-NaF PET combined with computed tomography (CT) angiography could identify aortic medial disease activity in patients with acute aortic syndrome. METHODS: Patients with aortic dissection or intramural hematomas and control subjects underwent 18F-NaF PET/CT angiography of the aorta. Aortic 18F-NaF uptake was measured at the most diseased segment, and the maximum value was corrected for background blood pool activity (maximum tissue-to-background ratio [TBRmax]). Radiotracer uptake was compared with change in aortic size and major adverse aortic events (aortic rupture, aorta-related death, or aortic repair) over 45 ± 13 months. RESULTS: Aortic 18F-NaF uptake co-localized with histologically defined regions of microcalcification and elastin disruption. Compared with control subjects, patients with acute aortic syndrome had increased 18F-NaF uptake (TBRmax: 1.36 ± 0.39 [n = 20] vs 2.02 ± 0.42 [n = 47] respectively; P < 0.001) with enhanced uptake at the site of intimal disruption (+27.5%; P < 0.001). 18F-NaF uptake in the false lumen was associated with aortic growth (+7.1 mm/year; P = 0.011), and uptake in the outer aortic wall was associated with major adverse aortic events (HR: 8.5 [95% CI: 1.4-50.4]; P = 0.019). CONCLUSIONS: In patients with acute aortic syndrome, 18F-NaF uptake was enhanced at sites of disease activity and was associated with aortic growth and clinical events. 18F-NaF PET/CT holds promise as a noninvasive marker of disease severity and future risk in patients with acute aortic syndrome. (18F Sodium Fluoride PET/CT in Acute Aortic Syndrome [FAASt]; NCT03647566).