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Introduction Systemic sclerosis (SSc) is a rare immune-mediated disease characterized by vasculopathy and fibrosis, potentially affecting major organs such as the heart. Cardiac involvement may include the pericardium, myocardium, valves, and conduction system, through mechanisms of inflammation, ischemia, and fibrosis, leading to a worse prognosis. Conduction disturbances are frequent in SSc and can occur early in the disease, even before fibrosis or other visceral manifestations, making early identification of high-risk patients essential.Material and Methods ObjectivesTo determine the proportion of SSc patients with arrhythmias or conduction abnormalities.To identify clinical and demographic features associated with these alterations.Methods We included patients with a confirmed diagnosis of SSc followed at Hospital Garcia de Orta, fulfilling the 2013 ACR/EULAR classification criteria, and registered in the Portuguese registry of rheumatic diseases ( Reuma.pt). Overlap syndromes were excluded. Arrhythmias and conduction abnormalities were identified through electrocardiogram (ECG) and/or 24/48-hour Holter recordings. Bivariate analysis was performed to evaluate associations with clinical and demographic characteristics.Results A total of 146 patients were included, of whom 12 (8.2%) presented arrhythmias and/or conduction abnormalities. The most prevalent arrhythmia was supraventricular extrasystole (50%, n=6), while the most frequent conduction disorder was right bundle branch block (33.3%, n=4). Only one case of left bundle branch block and one case of third-degree atrioventricular block were documented. Among these 12 patients, 10 (83.3%) were female and 11 (91.7%) Caucasian; 58.3% had diffuse cutaneous involvement and 41.7% limited cutaneous disease. Cardiovascular comorbidities included hypertension in 72.7% and coronary artery disease in 18.2%.Patients with conduction abnormalities had a higher median age at diagnosis (66.8 vs. 55.9 years). This group also showed a higher prevalence of anti-topoisomerase I antibodies (58.3% vs. 26.9%, p<0.041) and heart failure (27.3% vs. 4.8%, p<0.025).Conclusions In this cohort, 8.2% of SSc patients had arrhythmias or conduction abnormalities. Supraventricular extrasystoles were the most common arrhythmia, and right bundle branch block the most frequent conduction disorder. These findings may underestimate the true prevalence, as ECG and Holter monitoring were not systematically performed, potentially missing subclinical cases. Compared with the general population, where conduction abnormalities are reported in approximately 1–2% (depending on age and comorbidities), the prevalence observed in our cohort appears higher, highlighting the need for systematic cardiac evaluation in SSc. Furthermore, conduction abnormalities were associated with anti-topoisomerase I positivity and heart failure, underscoring the importance of early risk stratification and tailored surveillance in this patient group.Abstract P.154 Table 1