Longitudinal assessment of cardiac involvement in Erdheim-Chester disease using cardiac magnetic resonance imaging

7067 Background: Erdheim-Chester disease (ECD) is a rare multi-systemic non-Langerhans cell histiocytosis that affects the heart in nearly half of patients. Atrial infiltration and pericardial effusion are the hallmarks of cardiac involvement and can lead to clinical complications (conduction disorders, coronary artery stenosis, tamponade, constrictive pericarditis). Evolution under treatment is poorly studied. We aimed to investigate the evolution of cardiac involvement in ECD using cardiac magnetic resonance (CMR) imaging. Methods: All ECD patients with a CMR imaging disclosing a cardiac involvement and who underwent at least one follow-up CMR imaging between 2005 and 2020 at a French tertiary center were retrospectively included. First and last CMR imaging were compared. Multivariable analysis was performed to search for independent predictors of cardiac involvement resolution. Variables were included in the model if their P-value was < 0.1 on univariable analysis. Results: Overall, 46 patients were included. Median age at first imaging was 63 years [53-69]. Median delay between the first and the last imaging was 4 years [2-7]. BRAF V600E mutation was present in 43 patients (94%). Patients received a median of 2 [1-3] treatments. All patients (100%) had cardiac involvement at baseline. Right atrio-ventricular sulcus (RAVS) was infiltrated in 38 patients (83%) and was the main cardiac feature.Overall, complete regression was observed in 6 patients (13%), partial regression in 26 patients (56%), stable imaging in 12 patients (26%), and worsening in 2 patients (5%). In patients with RAVS infiltration, complete regression was observed in 5 patients (16%) and partial regression was seen 22 patients (58%) regression. On univariable analysis, patients with regression of their infiltration had a lower rate of death (16% versus 64%, P= 0.002), a higher rate of atrial infiltration late gadolinium enhancement (LGE) (97% versus 71%, P= 0.01), a higher rate of hydronephrosis (50% versus 14%, P= 0.03) and a lower rate of interferon prescription (69% versus 100%, P= 0.02). A similar rate of vemurafenib use was observed in both groups (69% versus 54%, P= 0.3). On multivariable analysis, death remained significantly associated with follow-up imaging status (ß = -2.3 P= 0.01), while atrial infiltration LGE (ß = 2.7, P= 0.06), hydronephrosis (ß = 1.6, P= 0.1) and treatment with interferon (ß = -16, P= 1) were no longer significantly associated with imaging status. Conclusions: Partial or complete resolution of cardiac involvement was observed in 69% of patients with ECD and was significantly associated with a lower rate of death on multivariable analysis.