Published: Dec 4, 2014
By Pauline Anderson , Contributing Writer, MedPage Today
Patients with idiopathic inflammatory myopathies (IIMs) seemed to have a greater burden of cardiovascular risk factors and a higher prevalence of severe coronary artery atherosclerosis compared with healthy controls, a multicenter study found.
Among IIM patients, 33% were obese (body mass index greater than 30 kg/m2)) versus 10% of controls, 71% had hypertension versus 42% of controls, and 13% had diabetes compared with none of the control patients, according to Louise Diederichsen, MD, PhD, of Odense University Hospital in Denmark, and colleagues.
In addition, median coronary artery calcification (CAC) scores, a subclinical measure of atherosclerosis arrived at through computed tomography (CT), were higher in the patients than controls, the researchers reported in Arthritis Care and Research.
IIMs such as polymyositis (PM) and dermatomyositis (DM) primarily affect proximal striated muscles and are characterized by muscle weakness and inflammatory infiltrates in the muscles. Affected patients have a higher mortality rate compared with the general population, mostly due to cardiovascular events.
The new study aimed to determine the prevalence of cardiovascular risk factors and CAC in patients with DM and PM, and whether traditional cardiovascular risk factors are associated with CAC.
The study included 76 patients with PM or DM, with a mean age of 60 and a mean disease duration of 9 years. Most (76%) were on immune-suppressants, including 54% who were taking conventional disease-modifying anti-rheumatic drugs (DMARDs), both as monotherapy and in combination with another DMARD or prednisolone. Upon inclusion, 57% received glucocorticoids.
Muscle biopsies determined that patients had varying degrees of necrosis, degeneration, and atrophy.
The study also enrolled 48 healthy controls matched for age and gender. The controls had no history of cardiovascular or rheumatic disease and were not taking any medication.
Study participants completed a questionnaire on medical conditions and current medications, smoking habits, heart symptoms, and family history of cardiovascular disease. Investigators measured height, weight and waist circumference, and took blood pressure readings. They also analyzed blood samples for HbA1c and lipid profiles, including triglycerides.
To assess coronary artery atherosclerosis, researchers used cardiac CT scans to detect the presence of calcification. They expressed CAC in Agatston units (U).
Compared with controls, patients with myositis more often had cardiopulmonary symptoms including dyspnea and palpitations (both P<0.0001). The prevalence of previous cardiovascular disease was 9% in patients versus none in the control group (P=0.04).
In addition to having more hypertension and diabetes than controls, patients tended to be more obese (P=0.005). Patients also had a higher mean waist/hip ratio.
More patients had high mean triglycerides levels ≥1.7 mmol/L (24% versus 19% of controls, P=0.46). While 11% of the patients had mean HbA1c levels of 48 mmol/mol or higher, none of the controls did (P=0.02).
Median Agatston scores were 18 U in myositis patients and 5 U in controls (P=0.27). The authors pointed out that ≥400 U, which is consistent with severe coronary atherosclerosis, was seen in 20% of the IIM patients or five times more frequently than in the controls.
In multivariate analyses, factors associated with CAC in patients included age (OR per year 1.1, 95% CI 1.0-1.2,P=0.02) and current smoking (OR compared with never smoked 10.6, 95% CI 1.5-77.1, P=0.02).
Although severe CAC was associated with traditional cardiovascular risk factors, it was “not associated with PM/DM per se,” the authors noted.
“Our findings support the notion that IIM is associated with accelerated atherosclerosis like other chronic inflammatory rheumatic diseases,” they concluded.
The study does not determine the mechanism behind the higher burden of cardiovascular risk factors, but long-term glucocorticoid treatment has been linked to such risk factors. Also, physical inactivity and cardiovascular risk factors are closely correlated and, as the authors pointed out, patients had impaired physical fitness, as reflected by their decreased muscle strength.
Accelerated atherosclerosis may also be attributed to persistent low grade inflammation, they added.
A limitation of the study was that it may have been underpowered although this may reflect the rarity of the disease. Additionally, the control group may have been skewed in favor of subjects with subclinical cardiovascular disease, and the study population was mostly Caucasian.
Further research is needed to determine whether modification of classic risk factors prevents coronary calcification and reduces CV mortality in myositis patients, the authors stated.
The study was supported by the Danish Rheumatism Association.
Diederichsen and co-authors disclosed no relevant relationships with industry.
Primary source: Arthritis Care and Research
Source reference: Diederichsen L, et al “Traditional cardiovascular risk factors and coronary artery calcification in adults with polymyositis and dermatomyositis — a Danish multicenter study” Arthritis Care Res 2014; DOI: 10.1002/acr.22520.