IIM-associated myocarditis was consistently associated with Raynaud phenomenon, aPL positivity and anti-Ro52 coexistence, and was associated with higher mortality than ILD, supporting hs-TnI-guided triage to CMR as part of systematic cardiac surveillance in IIM.
Key Findings
Results
Myocarditis confirmed by cardiovascular magnetic resonance was present in 6.3% of patients with idiopathic inflammatory myopathies.
Myocarditis was confirmed in 9 of 142 consecutive adult IIM patients (6.3%) at a single center between 2019 and 2025.
Myocarditis was confirmed by CMR according to the 2018 Lake Louise Criteria, performed at diagnosis and during follow-up.
There was no significant association between myocarditis and IIM class (P = 0.303).
Myocarditis was not significantly associated with the antisynthetase antibody subgroup (anti-Jo-1 + PL-12 + PL-7 + EJ; 5.8% vs. 6.7%, P = 1.000).
Results
Raynaud phenomenon was the strongest independent clinical predictor of myocarditis in IIM.
In univariable analysis, Raynaud phenomenon was associated with myocarditis with OR 13.6 (95% CI 2.3–80.0).
In the event-constrained multivariable model, Raynaud phenomenon remained independently associated with myocarditis (adjusted OR 13.1, 95% CI 1.5–112.7).
The multivariable models were pre-specified as parsimonious (two predictors) given the limited event count of 9 myocarditis cases.
Results
Antiphospholipid antibody positivity was independently associated with myocarditis in IIM.
In univariable analysis, aPL positivity was associated with myocarditis with OR 10.7 (95% CI 2.6–43.9).
aPL positivity was defined by Sydney criteria: ≥40 GPL/MPL units confirmed at ≥12 weeks.
In the multivariable model, aPL positivity remained independently associated with myocarditis (adjusted OR 7.2, 95% CI 1.4–36.0).
Results
Several other serological and clinical features were associated with myocarditis in univariable analyses.
Anti-Ro52 coexisting with MSA/MAA was associated with myocarditis (OR 8.7, 95% CI 2.2–34.8).
Anti-PM/Scl was associated with myocarditis (OR 7.1, 95% CI 1.6–30.3).
Fever was associated with myocarditis (OR 7.1, 95% CI 1.6–30.3).
ILD was associated with myocarditis (OR 4.7, 95% CI 1.1–20.3).
Results
High-sensitivity cardiac troponin I demonstrated excellent diagnostic performance for detecting myocarditis in IIM.
hs-TnI was markedly higher in myocarditis compared to non-myocarditis patients (median 366 vs. 3.5 ng/L; P < 0.001).
The area under the receiver-operating characteristic curve (AUROC) for hs-TnI was 0.91 (95% CI 0.83–0.98).
The authors concluded these findings support hs-TnI-guided triage to CMR as part of systematic cardiac surveillance in IIM.
Results
All-cause mortality was significantly higher in IIM patients with myocarditis compared to those without.
All-cause mortality was 44% in myocarditis patients vs. 9% in non-myocarditis patients (OR 7.95, 95% CI 2.0–31.5; log-rank P = 0.030).
Univariable Cox proportional-hazards regression showed HR 3.77 (95% CI 1.03–13.78; P = 0.044) for myocarditis.
After adjustment for ILD in the logistic model, myocarditis remained significantly associated with mortality (adjusted OR 5.9, 95% CI 1.3–26.1; P = 0.020).
After adjustment for myocarditis, ILD attenuated to a non-significant trend (adjusted OR 2.9, 95% CI 0.9–9.2; P = 0.073), suggesting myocarditis carries a greater independent prognostic impact than ILD.
What This Means
This research studied 142 patients with idiopathic inflammatory myopathies (IIM) — a group of diseases where the immune system attacks the muscles — to understand how often heart muscle inflammation (myocarditis) occurs and which patients are most at risk. Researchers found that about 1 in 16 IIM patients (6.3%) had myocarditis confirmed by a specialized heart MRI scan. Patients who had Raynaud phenomenon (a condition where fingers and toes turn white or blue in the cold), certain antibodies called antiphospholipid antibodies, and specific immune markers in their blood were significantly more likely to have myocarditis.
A key practical finding was that a blood test called high-sensitivity cardiac troponin I (hs-TnI) was very good at identifying which patients were likely to have myocarditis — patients with myocarditis had levels more than 100 times higher than those without (median 366 vs. 3.5 ng/L), and the test had strong diagnostic accuracy (AUROC 0.91). This suggests that routinely checking this blood test and using it to decide who needs a heart MRI could help detect myocarditis early in IIM patients.
Importantly, the study found that myocarditis was associated with a much higher risk of death (44% mortality) compared to patients without myocarditis (9% mortality), and this risk remained elevated even after accounting for lung disease, which is typically considered a major cause of death in IIM. This research suggests that myocarditis may be an underappreciated but serious complication of IIM, and that routine cardiac monitoring — including troponin testing to guide decisions about heart MRI — could be important for identifying and managing high-risk patients, though the authors note these findings need confirmation in larger, multi-center studies.
Álvarez-Troncoso J, Refoyo-Salicio E, Díaz-Planellas S, Carrasco-Molina S, Soto-Abánades C, Martínez-Robles E, et al.. (2026). Myocarditis in idiopathic inflammatory myopathies: serologic and clinical correlates in a single-center registry.. Rheumatology international. https://doi.org/10.1007/s00296-026-06159-4