Supplementary Material for: Temporal trends and burden of hospitalizations for presumed cardiac sarcoidosis

Introduction
Cardiac sarcoidosis is a potentially life-threatening manifestation of systemic sarcoidosis, yet its true prevalence remains uncertain. Improved imaging techniques and greater clinical awareness may have contributed to higher detection rates, but nationwide data on cardiac involvement and hospitalization burden in Switzerland are lacking. We aimed to characterize national trends, comorbidity patterns, and in-hospital outcomes of presumed cardiac sarcoidosis between 2010 and 2021.
Methods
This nationwide retrospective nested case-control study used the Swiss Federal Statistical Office hospitalization database. Presumed cardiac sarcoidosis was defined by co-occurrence of International Classification of Diseases, 10th Revision, German Modification (ICD-10-GM) codes for sarcoidosis (D86.0–D86.8) and cardiac involvement (I41, I42, I44, I45, I46, I49, I50), excluding coronary artery disease (I25). Controls were age-, sex-, and admission-month-matched sarcoidosis hospitalizations without cardiac involvement.
Results
Among 5,636 hospitalized sarcoidosis patients, 813 (14%) met criteria for presumed cardiac sarcoidosis. Between 2010 and 2021, the number of hospitalizations for presumed cardiac sarcoidosis increased significantly, approximately doubling over the study period (rate ratio 2.09, 95% CI 1.87–2.35; p<0.001). Over the same period, the proportion of patients carrying implantable cardiac devices doubled from 15% to 30% (+1.2% per year; 95% CI 0.3–2.1; p=0.015). Compared with controls, patients with presumed cardiac sarcoidosis had a greater comorbidity burden (median 10 vs 8), higher in-hospital mortality (5.5% vs 2.3%; OR 2.45 [1.59–3.85]), and more frequent rehospitalizations (0.32 vs 0.24 per year). In multivariable analyses, acute organ dysfunction was most strongly associated with in-hospital mortality, whereas heart failure and atrial fibrillation were the strongest predictors of rehospitalization.
Conclusion
Hospitalizations for presumed cardiac sarcoidosis in Switzerland have nearly doubled between 2010 and 2021, likely reflecting increased diagnostic awareness and improved detection, although a true increase in disease incidence cannot be excluded. Despite rising case numbers and higher comorbidity burden, overall in-hospital mortality remained stable.