When stratifying serum muscle damage marker levels according to the type of cardiac involvement identified (as per the MDAAT: myocardial, pericardial, arrhythmia or sinus tachycardia), only myocardial disease was associated with increasing levels of cTnT and cTnI [for cTnT: adjusted OR 1.00 (95% CI 1.00, 1.01), P = 0.006; for cTnI: adjusted OR 1.01 (95% CI 01.00, 1.02), P = 0.015] (supplementary Table S3, available at Rheumatology online). This evidence concerns the gene TNNT2 and cardiac arrhythmia.