AB0652 QTC INTERVAL PROLONGATION IN A SCANDINAVIAN COHORT OF PATIENTS WITH IDIOPATHIC INFLAMMATORY MYOPATHIES AND SYSTEMIC SCLEROSIS: CORRELATIONS WITH CLINICAL VARIABLES
Authors: Sine Søndergaard Korsholm, Maryam Dastmalchi, John Bonde Knudsen, Axel Cosmus Diederichsen, Ingrid E. Lundberg, Daniel C. Andersson, Nanna Witting, Søren Jacobsen, Tina Friis, Markus E. Krogager, Louise Pyndt Diederichsen
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Idiopathic inflammatory myopathies (IIM) are rare devastating diseases characterized by progressive muscle weakness and muscle fatigue. IIM frequently affects other organs pointing to IIM as a systemic inflammatory disease. Cardiac involvement is associated with poor prognosis. The symptoms are often subclinical and therefore overlooked. QTc prolongation has been detected in patients with systemic sclerosis (SSc). Autoantibodies are important diagnostic tools to confirm IIM and are present in approx. 60% of IIM patients. Autoantibodies are increasingly being recognized as markers for specific organ involvement. A biomarker for cardiac involvement has yet to be elucidated. <h3>Objectives</h3> The aim is to generate new knowledge about cardiac involvement in IIM detected by electrocardiography (ECG) and to evaluate possible associations between autoantibodies and cardiac involvement detected on ECG in a cohort of IIM patients compared with ECG changes in a cohort of SSc patients. <h3>Methods</h3> In a Scandinavian cohort, 263 IIM patients (130 polymyositis patients, 77 dermatomyositis patients, and 56 inclusion body myositis patients) and 102 SSc patients were investigated by ECG and basic cardiovascular and disease specific assessments according to international guidelines. IIM patients were tested for myositis specific autoantibodies (MSAs; anti-Jo-1, anti-PL-7, anti-PL-12, anti-OJ, anti-EJ, anti-SRP, anti-Mi-2, anti-MDA5, anti-TIF1 γ, anti-NPX2, anti-SAE1, anti-HMGCR) and myositis associated autoantibodies (MAAs; anti-PM/Scl75, anti-PM/Scl100, anti-Ro52, anti-Ku, anti-cN1A). <h3>Results</h3> Twenty two IIM patients (8.49%) had abnormal QRS duration versus one SSc patient (1.06%) (P = 0.012). SSc patients had significantly longer QTc duration than IIM patients (QTc = 432.7 ms ± 22.2 and 426.4 ms ± 23.6, respectively) (P = 0.03). Multivariate regression analysis revealed that increased C-reactive protein (CRP) (P = 0.008), gender (P = 0.002), and hypertension (P = 0.007) were associated with QTc duration in IIM patients. Likewise, pulmonary arterial hypertension was associated with QTc duration (P &lt; 0.001) in SSc patients. In analysis of pooled data for IIM patients and SSc patients, factors associated with QTc duration were increased CRP (P = 0.005), gender (P = 0.001), and hypertension (P = 0.01). <h3>Conclusion</h3> Both IIM patients and SSc patients had ECG changes though no particular pattern was shown. The findings support our hypothesis on cardiac involvement in IIM patients. No significant association was found between presences of either myositis specific or myositis associated autoantibodies and ECG changes. This could be due to the relatively low number of each autoantibody. There is a need to conduct larger prospective studies to identify a possible autoantibody for cardiac involvement in IIM. <h3>Acknowledgement</h3> The authors would like to thank all participating patients and the study personnel at the including centres. <h3>Disclosure of interests</h3> Sine Søndergaard Korsholm: None declared, Maryam Dastmalchi: None declared, John Bonde Knudsen: None declared, axel Cosmus Diederichsen: None declared, ingrid E. Lundberg Grant/research support from: Dr. Lundberg has received honoraria from Bristol Myers Squibb and MedImmune and is currently receiving a research grant from Bristol Myers Squibb and from astra Zeneca., Consultant for: She is a scientific advisor for Bristol Myers Squibb, and aTyr, Daniel C. Andersson: None declared, Nanna Witting: None declared, Søren Jacobsen: None declared, Tina Friis Grant/research support from: anti cN-1A ELISA kits and EUROLINE autoimmune inflammatory Myopathies 16 aG kits have been provided for a project free of charge from Euroimmun., Markus E. Krogager: None declared, Louise Pyndt Diederichsen: None declared