A Prospective Study on Autonomic Functions in Idiopathic Inflammatory Myopathies: The AFIIM Study

Dysautonomia in idiopathic inflammatory myopathies (IIM) is an underrecognized and poorly characterized manifestation, despite its potential implications for disease prognosis and clinical management. In this study, we assessed autonomic dysfunction in patients with IIM and investigated its correlation with cardiac imaging biomarkers based on cardiac magnetic resonance imaging (CMRI).

The study recruited clinically suspected IIM patients aged 10-60 years and age- and sex-matched healthy controls. Evaluations included myositis disease activity assessment tool (MDAAT), autonomic function testing (AFT), tilt table test (TTT), and CMRI with multiparametric mapping.

Among 31 diagnosed cases of IIM, 28 patients underwent AFT and TTT. Of these, 12 had dermatomyositis, 7 had overlap myositis, 7 had immune-mediated necrotizing myopathy, and 2 had anti-synthetase syndrome. The mean age of onset was 33±12.92 years, with an average illness duration of 16.63±19.43 months, and a female predominance (F:M = 2.1:1). The patients exhibited a lower median total autonomic power (563.2, interquartile range [IQR] = 209.6-1964.6 vs 1606.5, IQR = 1048.6-2676; P = 0.003). The TTT was positive in 10.9% cases. The mean standard deviation of normal-to-normal intervals (SDNN) was lower among the patients (31.7 ± 22.3 vs 43.4 ± 13.7; P = 0.023). SDNN and total autonomic power were negatively correlated with native-T1-mapping (ρ = -0.537, P = 0.009; ρ = -0.638, P = 0.007). An SDNN cut-off of ≤28.68 had a sensitivity of 83.3% and specificity of 76.0% (area under the curve [AUC] = 0.773, P = 0.030), whereas a total power of ≤725.81 had a sensitivity of 83.3% and specificity of 74.0% (AUC = 0.760, P = 0.039) in diagnosing cardiac involvement in IIM.

In this first-of-its-kind study integrating AFT and TTT with CMR to evaluate IIM, patients demonstrated significant autonomic dysfunction, with AFT parameters showing a correlation with CMR findings, thus indicating their potential as a simple predictor of cardiac involvement.