Background/Purpose: Idiopathic inflammatory myopathies (IIM) are a group of rare disorders that can affect the heart. It is unclear which patients are at higher risk. Anti-signal recognition particle (anti-SRP) antibody has been inconsistently suggested as a risk factor. This work aims to find predictors of heart involvement in IIM.

Methods: Multicenter open cohort study, including patients registered in the IIM module of the Rheumatic Diseases Portuguese Register (Reuma.pt/Myositis) until January 2022. Patients without heart involvement information were excluded. Myo(peri)carditis, dilated cardiomyopathy, conduction abnormalities and/or premature coronary artery disease were considered. Data from continuous variables are presented as mean ± standard deviation. Univariate analysis was performed using chi-square, Fisher’s exact, Mann-Whitney or t-test, as appropriate. Independent predictors of cardiac involvement, adjusted for sex and age at diagnosis, were identified through binomial logistic regression. The linearity of the continuous variables was assessed via the Box-Tidwell procedure. Correlated variables, cases with missing information and outliers were excluded from the multivariate analysis to assure the validity of the regression.

Results: 229 patients were included, 163 (71.2%) females. Patients were classified as having definite [56/115 (48.7%)], likely [23/115 (20.0%)], or possible [2/115 (1.7%)] IIM by 2017 EULAR/ACR classification criteria. Cardiac involvement was present in 11 (4.8%) patients (Figure 1), of whom 42.9% were classified as likely and 57.1% as definite IIM. The mean age at disease onset was 47.1 ± 19.0 years, the mean age at diagnosis was 48.6 ± 18.7 years, and the mean disease duration at the last follow-up was 7.0 ± 6.6 years. Compared to other IIM patients (Table 1), patients with cardiac involvement were older at disease onset (57.6 ± 11.9 vs 46.6 ± 19.2 years, p=0.035) and diagnosis (58.3 ± 12.2 vs 48.0 ± 18.9 years, p=0.049), and had a shorter disease duration at the last follow-up (3.9 ± 4.1 vs 7.2 ± 6.7 years, p=0.019). Clinically, patients with cardiac involvement had a lower manual muscle testing score (MMT), comparing the lowest value throughout follow-up, and more frequently had esophageal [5/10 (50.0%) vs 34/208 (16.3%), p=0.018] and lung involvement [9/11 (81.8%) vs 68/217 (31.3%), p=0.001]. Conversely, this group less frequently had Gottron’s sign [1/10 (10.0%) vs 68/153 (44.4%), p=0.045]. Anti-SRP antibodies were more commonly identified in patients with cardiac involvement [3/9 (33.3%) vs 10/175 (5.7%), p=0.018]. No differences were found between the two groups for other demographical or clinical data or serum biomarkers. In the multivariate analysis, lung involvement (OR 7.064, 95%CI: 1.246-40.057, p=0.027) and positivity of anti-SRP antibodies (OR 7.886, 95%CI: 1.333-46.666, p=0.023) were confirmed as independent predictors of heart involvement in IIM patients, regardless of sex and age at diagnosis.

Conclusion: Lung involvement and anti-SRP antibodies were independent predictors of heart involvement in our cohort of IIM patients. We suggest considering a closer screening for heart involvement in these patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cardiac-involvement-in-idiopathic-inflammatory-myopathies-when-should-we-look-for-it/