Ab1290 Gca Relapses More Often in the Subclavian Arterial System

Background: Ultrasonography (US) for diagnosis of large vessel vasculitis (LVV) is a recommended first line diagnostic procedure. We have been running an US led diagnostic pathway in our centre since January 2017. This pathway is also used to diagnose relapsing disease including in patients who are present with proximal shoulder girdle pain and stiffness. Objectives: To compare the anatomical distribution of relapsing disease with that at diagnosis. Methods: Patients in whom new and relapsing disease was diagnosed using US were included. Protocolised US examination of the common carotid system of arteries and those of the subclavian system of arteries were carried out at diagnosis and relapse. Halo sign in at least two different arteries was needed for establishing new or relapsing disease. Disease characterisation was classified as being in the carotid system, subclavian system, or both. The nature of the disease at relapse was compared to that at diagnosis. Results: 279 patients were diagnosed with LVV using US since Jan 2017. 57 (20%) were diagnosed as having a relapse using US. 43/57 (75%) and 28/57 (49%) had involvement of the carotid system at baseline and relapse respectively. 22/57 (39%) and 44/57 (77%) had involvement of the subclavian system at baseline and relapse respectively. A Sankey Graph comparing the nature of involvement at diagnosis and relapse is as in Figure 1. Conclusion: The branches of the common carotid artery (external carotid artery) are commonly involved at diagnosis, but relapse tends to occur more frequently in the subclavian artery branches. This is especially true where baseline disease was established in the carotid system. The presentation of patients with subclavian system disease is often with only constitutional symptoms and with shoulder girdle pain and stiffness. This may be mistaken for being a polymyalgia rheumatica relapse. It is essential to examine the subclavian system of arteries before diagnosing polymyalgia rheumatica relapse in individuals with LVV. REFERENCES: [1] Hellmich B, et al. 2018 Update of the EULAR recommendations for the management of large vessel vasculitis. Ann Rheum Dis. 2020 Jan;79(1):19-30. [2] Mukhtyar C, et al. Improving the quality of care for people with giant cell arteritis. Clin Med (Lond). 2021 Jul;21(4):e371-e374. Acknowledgements: NIL. Disclosure of Interests: None declared.