P36 Lupus myocarditis: the role of cardiac MRI and endomyocardial biopsy as diagnostic parameters

Abstract

<h3>Background</h3> Lupus myocarditis (LM) is a rare but potentially fatal complication occurring in 5–10% of patients with systemic lupus erythematosus (SLE). Endomyocardial biopsy (EMB) is regarded as the diagnostic gold-standard for myocarditis but is invasive and validated in the context of non-rheumatological myocarditis. 2D-echocardiography and cardiac magnetic resonance (CMR) incorporating T1 and T2-mapping, are non-invasive diagnostic tools used to evaluate myocarditis. Current international guidelines on the use of EMB and CMR in myocarditis are based on research done in predominantly non-SLE populations. <h3>Objectives</h3> To evaluate the diagnostic role of CMR and EMB in patients with LM. <h3>Method</h3> We conducted a cross-sectional study including 13 SLE patients without features of LM and 13 symptomatic LM patients between May 2022 and October 2023. Both cohorts were investigated with 2D-echocardiography (including speckle tracking: global longitudinal strain (GLS) analyses) and CMR (T1/T2-mapping). EMB was performed in all symptomatic LM patients. <h3>Results</h3> All patients were female, with a mean age of 31 (SD±9.3) and 32 (SD±9.7) years in the LM and control groups respectively. Patients with LM had a higher disease activity than those without (median SLEDAI 12 [IQR:9–14] v 8 [IQR:4–15]). On EMB, a lymphocytic infiltrate was demonstrated in 3/13 patients (23.1%) with a CD3⁺/CD45⁺ predominant infiltrate on immunohistochemistry in 46.2%. No patient fulfilled the Dallas Criteria for myocarditis. Of 12 LM patients who underwent CMR, nine (75%) met the 2018 Lake Louise criteria (LLC) for myocarditis. Although no control patient fulfilled the LLC, regional and/or global left ventricular dysfunction (2D-echocardiography) was detected in 7/12 and abnormal T1-relaxation (CMR) in 5/12 asymptomatic patients. <h3>Conclusion</h3> In a cohort of 26 SLE patients, 75% of patients with active LM fulfilled the 2018 CMR Lake Louise Criteria for myocarditis. Evidence of left ventricular dysfunction and abnormal myocardial tissue properties were however also detected in asymptomatic SLE patients. Future research is necessary to delineate the optimal use of CMR in differentiating clinically relevant LM from subclinical disease. Endomyocardial biopsy, even though safe, is invasive and when applying standard histological diagnostic criteria, had limited utility in symptomatic LM patients.