Patients with dermatomyositis or polymyositis are at increased risk for arterial thrombotic events that immunosupressant use may lessen, according to a case-control study.
These autoimmune diseases are known to cause muscle inflammation, weakness, and significant morbidity. However, there are fewer data on the risk for arterial events in affected patients.
So Dr. Christian A. Pineau and colleagues assessed 607 people with dermatomyositis (DM) or polymyositis (PM). The researchers measured events such as acute myocardial infarction, stroke, and ischemic heart disease in this cohort during 1994–2003.
Patients were identified from the province of Quebec's physician billing, hospitalization, and pharmacy databases. Their average age was 62 years, and women accounted for 70% of the cohort. All patients were beneficiaries of the public drug insurance plan, which covers approximately 42% of the residents of Quebec. The investigators reported their findings in the Journal of Rheumatology (2009 July 31 [doi:10.3899/jrheum.090061
Results suggest a high incidence of arterial events in DM and PM. There were 124 arterial events experienced by 80 patients during the study period. Events included 34 incident cases of acute MI (equivalent to 13.8 per 1,000 person-years). The investigators estimated that they would expect about 17 acute MIs during this time in the same number of people in the general population, so the study cohort's relative risk was 1.95.
There were 13 strokes during the study (a rate of 5.2 per 1,000 person-years), similar to the rate of 5.1 per 1,000 person-years reported in rheumatoid arthritis (Ann. Rheum. Dis. 2006;65:1608–12). Stroke incidence in the general Canadian population is estimated at 3.1 per 1,000 person-years, suggesting a near doubling of risk for people with one of these inflammatory myopathies.
“As rheumatologists, we should be sensitive to the fact that comorbidities such as coronary artery disease represent a high burden for our patients,” said Dr. Pineau, a rheumatologist at McGill University Health Centre in Montreal.
Nonatherosclerotic heart disease, hypertension, and lipid disorders were important determinants of arterial events in the study. For example, risk for an event in someone with a lipid disorder carried an adjusted rate ratio of 4.9; heart failure or valve disease, 3.0; and hypertension, 2.5, according to a multivariate analysis.
In contrast, exposure to nonsteroidal immunomodulators was associated with a significantly lower arterial event rate (adjusted RR, 0.5). “The use of immunosuppressants, which improve disease control and minimize the need for steroids, could in theory have the potential to lower the risk of coronary artery disease,” Dr. Pineau said.
A majority (85% of the cohort) was exposed to systemic glucocorticoids; 26% to methotrexate; 21% to azathioprine; 14% to antimalarial drugs; and 6% to cyclophosphamide.
An unanswered question is why the researchers found a higher rate of arterial thrombotic events for people with DM or PM, compared with the general population. “I would like rheumatologists to see all rheumatic diseases in the same light as they see rheumatoid arthritis,” Dr. Pineau said.
Although the use of disease-modifying antirheumatic drugs is the cornerstone of therapy in rheumatoid arthritis, many rheumatic diseases such as PM and DM are primarily—and often exclusively—treated with steroids, he said. At the same time, other immunosuppressants take only a secondary role. “As exemplified in this study, this strategy could potentially lead to increased morbidity, either through the toxicity associated with the use of higher steroid doses, or because of a higher inflammatory burden brought upon by a suboptimal control of the disease.”
The study was supported by a grant from the Canadian Institutes of Health Research. Dr. Pineau had no relevant disclosures. Additional research in this area is warranted, the authors wrote.