Systemic Sclerosis Portends Increased Risk of Conduction and Rhythm Abnormalities at Diagnosis and During Disease Course: A US Population-Based Cohort.

Objectives: To study the incidence, risk factors and outcomes of conduction and rhythm disorders in a population-based cohort of patients with systemic sclerosis (SSc) vs. non-SSc comparators. Methods: An incident cohort of patients with SSc (1980-2016) from Olmsted County, MN was compared to age- and sex-matched non-SSc subjects (1:2). Electrocardiograms (ECGs), Holter ECGs, and need for cardiac interventions were reviewed to determine the occurrence of any conduction or rhythm abnormalities. Results: 78 incident SSc cases and 156 comparators were identified (mean age 56 y, 91% female). The prevalence of any conduction disorder prior to SSc diagnosis compared to non-SSc subjects was 15% vs. 7% (p=0.06), and any rhythm disorder was 18% vs. 13% (p=0.33). During a median follow-up of 10.5 years in patients with SSc and 13.0 years in non-SSc comparators, conduction disorders developed in 25 patients with SSc with cumulative incidence of 20.5% (95% CI: 12.4-34.1%) vs. 28 non-SSc patients with cumulative incidence of 10.4% (95% CI: 6.2-17.4%) (HR: 2.57; 95% CI: 1.48-4.45), while rhythm disorders developed in 27 patients with SSc with cumulative incidence of 27.3% (95% CI: 17.9-41.6%) vs. 43 non-SSc patients with cumulative incidence of 18.0% (95% CI: 12.3-26.4%) (HR: 1.62; 95% CI: 1.00-2.64). Age, pulmonary hypertension and smoking were identified as risk factors. Conclusion: Patients with SSc have an increased risk of conduction and rhythm disorders both at disease onset and over time, compared to non-SSc patients. These findings warrant increased vigilance and screening for ECG abnormalities in SSc patients with pulmonary hypertension.