SAN DIEGO – Patients with systemic sclerosis are at greater than eightfold increased risk of having an acute myocardial infarction during the first year after diagnosis, compared with matched controls, according to the first large population-based cohort study to look at the issue.
After that first year, the MI risk drops off over time. Still, during years 1-5 post diagnosis the MI risk remains more than triple that of the matched general population, Dr. J. Antonio Avina-Zubieta reported at the annual meeting of the American College of Rheumatology.
"Our findings support increased vigilance in cardiovascular disease prevention, surveillance, and risk modification in patients with systemic sclerosis," declared Dr. Avina-Zubieta, a rheumatologist at the University of British Columbia, Vancouver.
Dr. J. Antonio Avina-Zubieta
He and his coinvestigators harnessed comprehensive provincial medical databases to identify all 1,245 adults diagnosed with rheumatologist-confirmed systemic sclerosis (SSc) in British Columbia during 1996-2010. The SSc patients averaged 53 years of age at the time of their rheumatologic diagnosis. Eighty-three percent were women.
During a mean follow-up period of 3.5 years following diagnosis of SSc, 89 patients experienced an acute MI, as did 289 controls. This translated to an incidence rate of 20.2 cases per 1,000 person-years among patients with SSc, compared with 5.3 per 1,000 among controls.
The risk was 8.2-fold greater in SSc patients than controls during the first year after diagnosis and 3.5 times greater during years 1-5 after diagnosis, but once patients got more than 5 years out from diagnosis there was no longer any significant increase in MI risk.
Patients with SSc who were in the 45- to 59-year-old age group were at greatest risk: They were 7.4 times more likely than controls to have an MI. SSc patients aged 60-74 years had a 4.4-fold greater risk of MI than did controls, and those aged 75 years and older were at 5.6-fold increased risk.
The SSc patients remained at a 4.3-fold increased risk of MI, compared with controls, in a multivariate analysis extensively adjusted for baseline chronic obstructive pulmonary disease, angina, obesity, hormone replacement therapy, Charlson Comorbidity Index, number of hospitalizations during the 12 months prior to diagnosis, and the use of NSAIDs, COX-2 inhibitors, glucocorticoids, lipid-lowering drugs, and antidiabetic medications.
It is well established that patients with rheumatoid arthritis or systemic lupus erythematosus have an increased risk of premature atherosclerotic disease. Up until now, however, information about the risk of major adverse cardiovascular events in patients with SSc has been scarce and has come from nondefinitive studies in selected populations or cross-sectional studies lacking adequate adjustment for potential confounding factors, according to Dr. Avina-Zubieta, who also is a research scientist at the Arthritis Research Centre of Canada in Richmond, B.C.
Why the sharp increase in MI risk during the first year after diagnosis of SSc? He offered two hypotheses. One is that this is a time of particularly great inflammatory load as physicians work to get the disease under control. Also, there is a phenomenon Dr. Avina-Zubieta called "the depletion of susceptibles," whereby, once the patients at higher risk have had their MI early on, those who remain aren’t at sufficient risk to stand out from the general population.
The study was sponsored by the Arthritis Centre of Canada. Dr. Avina-Zubieta reported having no financial conflicts of interest.