Objective To compare systolic cardiac function in patients with juvenile dermatomyositis (JDM) with matched controls and examine associations between systolic and diastolic cardiac function and disease variables.

Methods Fifty-nine patients, examined at follow-up, median 16.8 years (2–38 years) after disease onset, were compared with 59 age-matched and sex-matched controls. Echocardiography was performed and analysed blinded to patient information. We used mitral annulus displacement to assess the relative long-axis shortening of the left ventricle (long-axis strain) and early diastolic tissue velocity (e′), as markers for systolic and diastolic function, respectively. Disease activity and organ damage were assessed at follow-up by clinical examination and retrospectively by chart review.

Results Long-axis strain was reduced in patients compared with controls (16.6% (2.5) vs 17.7% (2.0), mean (SD), p=0.001), whereas no difference was seen between patients with active and inactive disease. Disease duration correlated with systolic and diastolic function (r_sp=−0.50 and r_sp=−0.73, both p<0.001) and so did Myositis Damage Index (MDI) 1 year (r_sp=−0.36 and r_sp=−0.46) and MDI at follow-up (r_sp=−0.33 and r_sp=−0.60), all p<0.01. High early disease activity score (DAS) in skin (DAS skin 1 year), but not in muscle, predicted systolic (standardised β=−0.28, p=0.011, R²=48%) and diastolic dysfunction (β=−0.36, p<0.001, R²=72%) at follow-up.

Conclusions Long-axis strain was reduced in JDM patients compared with controls, suggesting systolic dysfunction. Impaired systolic and diastolic function was predicted by DAS skin 1 year. This indicates a common pathway to two different cardiac manifestations in JDM, perhaps with similar pathogenesis as skin affection.