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