Evaluation of aortic inflammation in marfan syndrome patients with 18-fluorodeoxyglucose positron emission and computed tomography

Abstract Background The role of inflammation in Marfan Syndrome (MS) has been well studied in current research. These studies have investigated the role of serum Interleukin 6 (IL-6), Transforming Growth Factor-b (TGF-b) and Macrophage Colony Stimulating Factor (MCSF) as biomarkers of disease severity and progression. Surgical repair is the recommended treatment of aortic aneurysms when aortic diameter reaches the indication threshold. It has been observed however that dissection may occur even before this threshold is reached. 18-fluorodeoxyglucose (18 F-FDG) positron emission tomography / computed tomography (PET/CT) is the gold standard imaging modality to noninvasively assess vascular inflammation. Purpose Our aim was to investigate whether MS patients have increased aortic wall inflammation as assessed by 18F-FDG PET/CT, and the relationship between aortic wall inflammation with serum levels of IL-6, TGF-b and MCSF. Methods The study population consisted of fifteen MS patients and seventeen sex and age matched controls. In all subjects, serum levels of circulating IL-6, TGF-b and MCSF were measured. In PET/CT, the arterial target-to-background ratio (TBR) was calculated for aortic root (AR), ascending aorta(As), aortic arch (AA) and descending aorta (DA). Also, all patients were assessed with transthoracic echocardiography where the diameters of AR, As, AA, and DA were estimated at baseline and were reexamined at the end of the follow up period. Results TBR for MS vs. controls was 2.17±0.75 vs 2.01±0.36, p=0.75 at AR; 2.15±0.67 vs 1.84±0.35, p=0.040 at As; 2.16±0.64 vs 1.70±0.25, p=0.03 at AA and 1.97±0.52 vs 1.83±0.42, p=0.23 at DA respectively. Additionally, Marfan patients had increased levels of serum biomarkers. However, this difference was statistically significant (SS) only for IL-6 serum levels; 2.17±0.46 vs 1.08±0.12 p=0.011 and IL-6 was SS associated with AR TBR (rho=0.572, p=0.033), As TBR (rho=0.604, p=0.022) and DA TBR (rho=0.714, p=0.004). Two of our patients were operated due to severe dilatation of the aortic root and the surgical specimens showed aortic wall inflammation of moderate severity along with fibrosis. Conclusion MS patients have increased of aortic wall inflammation as assessed by 18F-FDG PET/CT, a finding that highlights the role of inflammation in the pathway of disturbed TGF signaling. Further research is needed to determine its prognostic role and value in identifying patients with an indication for early intervention.