Study Finds Possible Overlooked Risk Factor for Heart Attack

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New study results presented at the annual meeting suggest that immunoglobulin G4 (IgG) antiphospholipid antibody positivity may be an important but overlooked risk factor for myocardial infarction (MI).

The researchers examined antiphospholipid syndrome (APS), also known as antiphospholipid antibody syndrome, an autoimmune disease that most often affects young women. Patients with APS make abnormal proteins called antiphospholipid autoantibodies (aPLs) in the blood. The antibodies target proteins in the circulation and in cellular membranes, and some can interfere with the clotting system. People with APS may otherwise be healthy, but many also suffer from another underlying rheumatic disease, most frequently systemic lupus erythematosus.

APS is diagnosed when arterial, venous, or microvascular thrombosis or obstetric morbidity occur with confirmed, positive blood tests for aPLs. Long-term anticoagulation treatment prevents new thrombotic events in most patients with APS. However, conflicting information exists about the occurrence of pro-thrombotic aPLs in MI cases. Reasons include limited sample sizes, selected populations, and non-standardized research methods.

Therefore, the research team in Sweden studied “a large cohort of well-characterized patients with a first-time MI and an age- and gender-matched population controls.” Patients were divided into two groups: (1) 805 patients younger than 75 years who were studied 6 to 10 weeks after their first MI; and (2) 805 age-, sex-, and area-matched controls who had not had MI.

According to results, aPL IgG positivity remained associated with MI, even after the researchers adjusted for traditional cardiovascular risk factors such as smoking, hypertension, diabetes, and body mass index. The researchers concluded that IgG positivity is strongly and independently associated with MI. They said it could be an important—but neglected—risk factor in one of 10 MI patients in the general population.

“If our results and hypotheses are confirmed, aPL testing may become part of routine MI care and help identify [patients with] MI who are at high risk for complications and who may benefit from anticoagulation treatment as protection from future vascular events,” said co-author Elisabet Svenungsson, MD, of Karolinska Institutet/Karolinska University Hospital in Sweden.