Increased risk of acute myocardial infarction in Swedish patients with systemic sclerosis: a population-based study

Objectives To study the risk of acute myocardial infarction (AMI) in patients with SSc in a population-based cohort.Methods Using nationwide Swedish registers, we identified patients with incident SSc 2004-19 and age- and sex-matched comparators from the general population (1:10). Our primary outcome was incident AMI or death from incident AMI. We started follow-up from SSc diagnosis until the primary outcome, death from other cause than AMI, emigration or study end (31 December 2019). We estimated crude AMI incidence rate. We used flexible parametric models to explore the relative risk of AMI over time since diagnosis. We also used age as time scale to explore how AMI risk changes over increasing age. We also studied the outcomes of AMI in SSc compared with the matched comparators.Results We identified 1579 patients and 16 064 comparators. The incidence rate of AMI was 75.2 (95% CI 58.8-94.6) per 10 000 person-years in patients with SSc and 37.5 (95% CI 34.0-41.3) in the comparators, median follow-up was 5.2 and 6.3 years, respectively. The adjusted hazard ratio (HR) was highest during the first year after SSc diagnosis (HR 3.1, 95% CI 2.0-4.6). In patients with SSc, the risk of AMI increased more rapidly with increasing age compared with the comparators. AMI in SSc was associated with higher risk of mortality (HR 2.7, 95% CI 1.6-4.4) but not 30-day readmission (HR 1.3, 95% CI 0.7-2.0) compared with the comparators.Conclusion In line with previous studies, SSc is associated with a 2-fold increase in AMI incidence compared with the general population. What does this mean for patients?SSc is a rheumatic condition that causes hardening of the skin and internal organs. The disease can affect the heart and potentially increase the risk of myocardial infarctions (heart attacks). In our study, we compared the risk of myocardial infarction in patients with SSc to that of the general population of Sweden, ensuring both groups had similar age and sex distributions. We also examined when the risk was highest for patients with SSc, whether it is soon after diagnosis or later, as well as what happened after myocardial infarction. Our findings revealed that patients with SSc had twice as high a risk of myocardial infarction as the general population. This risk was particularly high shortly after an SSc diagnosis. Additionally, myocardial infarction in patients with SSc tend to be more severe, resulting in higher death rates. Our results highlight the importance of increased awareness of myocardial infarction risk factors in patients with SSc.