Increased incidence of sudden cardiac death in systemic sclerosis: data from a nationwide cohort study

OBJECTIVE: To evaluate incidence and risk factors of sudden cardiac death (SCD) in systemic sclerosis (SSc). METHODS: Individuals with SSc from the Australian Scleroderma Cohort Study meeting ACR/EULAR criteria were included. International Classification of Diseases (ICD)-10 code cause of death was sourced from the Australian National Death Index. "Presumed" SCD was defined as primary cause of death being an acute cardiovascular pathology (e.g., cardiac arrest, myocardial infarction). Between-group comparisons (presumed SCD vs. overall cohort) and multivariable Cox proportional hazard modelling were used to identify SCD associations. RESULTS: Among 1708 SSc patients, 32 SCD events occurred (1.9%) over 10,650 person-years of follow-up, giving an incidence rate of 300/100,000 person-years (PY). This rate is 3-9 times higher than published community estimates (35-89/100,000PY). Participants with SCD were more likely to have a history of coronary artery disease (CAD; 40.6% vs. 13.8%, p < 0.001), reduced left ventricular ejection fraction (LVEF; 18.5% vs. 5.5%, p = 0.004) and elevated NT-proBNP (33.3% vs. 11.5%, p = 0.042). SSc heart involvement occurred in 18.8% of SCD cases and 9.4% of the remaining cohort (p = 0.074). Multivariable modelling identified that older age (hazard ratio(HR)1.15 (95% confidence interval(CI)1.10-1.20), p < 0.001), CAD (HR2.28 (95%CI1.04-5.00), p = 0.040), reduced LVEF(HR2.89 (95%CI1.06-7.90), p = 0.038) and smoking history(HR2.80 (95%CI1.21-6.49), p = 0.016) were associated with SCD. CONCLUSION: SCD occurred in 1.9% of a large SSc cohort, with an incidence rate of 300/100,000PY, representing a significant increased frequency compared to the general population. Older age, CAD, reduced LVEF and smoking history were key risk factors, highlighting important and potentially modifiable risk factors for SCD in SSc.