Early Cardiac Involvement in Treatment-Naïve, Autoantibody-Seropositive Patients with Autoimmune Rheumatic Diseases in the Prodromal Phase—A Cardiovascular Magnetic Resonance Study

Background: Autoimmune rheumatic diseases (ARDs) often present diagnostic challenges, particularly in undifferentiated disease or overlap syndromes. Autoantibodies (AABs) serve as early biomarkers, but their relationship with cardiac involvement during the prodromal phase remains unclear. We hypothesized that cardiac involvement is an early, unifying feature in AAB-seropositive patients with suspected ARD/overlap syndromes but an as-of-yet unclear diagnosis. Methods: We prospectively recruited 18 treatment-naïve patients (mean age 52 ± 17 years, 94.4% women) with suspected undifferentiated ARD/overlap syndromes who were seropositive for myositis-specific (MSAs), myositis-associated (MAAs), or scleroderma-specific autoantibodies (SScSAs). All underwent comprehensive rheumatologic, pulmonologic, and cardiac evaluations, including multiparametric cardiovascular magnetic resonance (CMR) to assess myocardial inflammation, edema, and fibrosis. Results: Despite normal echocardiograms, electrocardiograms, and inflammatory biomarkers, all patients exhibited CMR evidence of cardiac involvement. Active myocardial inflammation (revised Lake Louise criteria) was confirmed in 66.7%, while subepicardial fibrosis was universal (median 5.0% of LV mass). During the 12-month follow-up, all patients with evidence of inflammation received immunosuppressive and cardioprotective therapy, leading to symptomatic improvement in all and reduced inflammation in 75% of repeat CMRs (3/4 patients). A definitive rheumatologic diagnosis was established in all cases, with 50% classified as overlap syndromes. Conclusions: Cardiac involvement is a highly prevalent disease manifestation in AAB-seropositive patients with suspected ARD/overlap syndromes and can be detected by CMR during the prodromal phase, even before diagnostic criteria are met. These findings support early CMR integration in the workup of such patients to guide timely immunosuppressive and cardioprotective interventions.