Myocarditis in anti-synthetase syndrome: clinical features and diagnostic modalities

Objectives: Myocarditis is an overlooked manifestation of anti-synthetase syndrome (ASS). Our study describes the clinical and instrumental features of ASS myocarditis and evaluates the performance of cardiac MRI (CMRI) with mapping techniques in assisting diagnosis of ASS myocarditis. Methods: Data from patients with ASS were retrospectively analysed. CMRI data for patients diagnosed with myocarditis, including late gadolinium enhancement (LGE), T2 ratio, T1 mapping, extracellular volume (ECV) and T2 mapping, were reviewed. Myocarditis was defined by the presence of symptoms and/or signs suggestive for heart involvement, including increased high-sensitive troponin T (hs-TnT) and/or N-terminal pro-brain natriuretic peptide (NT-proBNP), and at least an instrumental abnormality. The clinical features of patients with ASS with and without myocarditis were compared. A P-value of <0.05 was considered statistically significant. Results: Among a cohort of 43 patients with ASS [median age 58 (48.0-66.0) years; females 74.4%; anti-Jo1 53.5%], 13 (30%) were diagnosed with myocarditis. In 54% of those 13 patients, myocarditis was diagnosed at clinical onset. All patients with ASS with myocarditis had at least one CMRI abnormality: increased ECV in all cases, presence of LGE in 91%, and increased T1 and T2 mapping in 91%. The 2009 Lake Louise criteria (LLC) were satisfied by 6 patients, and the 2018 LLC by 10 patients. With the updated LLC, the sensitivity for myocarditis improved from 54.6% to 91.0%. Patients with ASS with myocarditis were more frequently males (53% vs 13%; P = 0.009) with fever (69% vs 17%; P = 0.001), and had higher hs-TnT [88.0 (23.55-311.5) vs 9.80 (5.0-23.0) ng/l; P < 0.001], NT-proBNP [525.5 (243.5-1575.25) vs 59.0 (32.0-165.5; P = 0.013) pg/ml; P = 0.013] and CRP [7.0 (1.7-15.75) vs 1.85 (0.5-2.86) mg/l; P = 0.011] compared with those without myocarditis. Conclusion: In ASS, myocarditis is frequent, even at clinical onset. Patients with ASS with myocarditis frequently presented with fever and increased CRP, suggesting the existence of an inflammatory phenotype. The use of novel CMRI mapping techniques may increase diagnostic sensitivity for myocarditis in ASS.