Antiphospholipid Antibodies Linked to Future CV Events

April 06, 2023

The presence of antiphospholipid antibodies is associated with an increased risk for future cardiovascular events, according to a new study.

The findings point to possible new approaches to risk stratification and the potential for new therapeutic targets in heart disease.

"In this study of the general population, we found that two antiphospholipid antibodies were associated with an increased risk of having a serious cardiovascular event over a follow up of 8 years," co-author Jason Knight, MD, University of Michigan, Ann Arbor, told | Medscape Cardiology.

"If confirmed in further studies, these findings could be used to identify a subgroup of patients who need more careful monitoring and more aggressive risk-factor modification, and if the increased risk linked to these antibodies is high enough, it may also justify preemptive treatments such as the anticoagulants that are routinely used in antiphospholipid syndrome," Knight said.

"The long-term vision is that we may identify some people in the general population who would benefit from treating the immune system for the prevention and treatment of cardiovascular disease instead of, or in addition to, using typical cardiovascular medications," he added.

The study was published online April 4 in JAMA Network Open.

Individuals with autoimmune and inflammatory diseases have a greater risk for cardiovascular events than expected based on traditional cardiovascular risk factors, with mechanisms proposed to explain this risk including inflammation-mediated disruption of vascular integrity and activation of platelets and coagulation pathways, the authors explain. However, the role of autoantibodies remains unclear.

They note that antiphospholipid antibodies can activate endothelial cells, platelets, and neutrophils, and some patients with persistently circulating antiphospholipid antibodies can develop antiphospholipid syndrome — an acquired thrombo-inflammatory disease characterized by arterial, venous, and microvascular thrombotic events and obstetric complications.

Cross-sectional studies have shown that antiphospholipid antibodies are acutely present in up to 17.4% of patients with stroke or transient ischemic attack, and small cohort studies have suggested that such antibodies may be present in 1%-12% of seemingly healthy individuals. However, the impact of sex, race, and ethnicity on the prevalence of antiphospholipid antibodies and their association with atherosclerotic cardiovascular disease is not known.

The researchers conducted the current study to look at the association between antiphospholipid antibodies and future risk for atherosclerotic cardiovascular events.

They analyzed data from 2427 participants in the population-based Dallas Heart Study who had no history of atherosclerotic cardiovascular disease or autoimmune diseases requiring immunosuppressive medications at the time of blood sampling at study entry in 2007-2009.

Eight different types of antiphospholipid antibodies were measured, and data on cardiovascular events over the next 8 years was recorded.

Results showed that 14.5% of the cohort tested positive for one of these antiphospholipid antibodies at the start of the study, with approximately one third of those detected at a moderate or high titer.

The researchers also found that the immunoglobulin A (IgA) isotypes of two antiphospholipid antibodies — anticardiolipin and anti-beta-2 glycoprotein — were associated with future atherosclerotic cardiovascular events.

After adjustment for other known risk factors, individuals testing positive for the IgA isotype of anticardiolipin had an almost five times increased risk (hazard ratio [HR], 4.92) of the primary endpoint (myocardial infarction, stroke, coronary revascularization, or cardiovascular death); while those testing positive for anti-beta-2 glycoprotein had an almost three times increased risk (HR, 2.91).

Furthermore, there was what appeared to be a dose effect. People with the highest levels of these antibodies also had the highest risk for cardiovascular events, with up to an almost 10-fold increased risk with the higher level of anticardiolipin. 

Knight said that more research into the IgA isotypes of these antiphospholipid antibodies is needed.

"Most of the mechanistic work in the antiphospholipid syndrome field has focused on IgG antiphospholipid antibodies. While we commonly find these IgA antibodies in patients with APS, the extent to which they contribute to disease has not been firmly established," he said. "The fact that IgA was the primary hit in our unbiased screen suggests that there is more to the story and we need to better understand the implications of having these antibodies in circulation, and what specific problems they may be causing."

Noting that antiphospholipid antibodies can form transiently after certain situations, such as infections, Knight said that further studies were needed with repeat blood testing to detect the chronic presence of the antibodies.  

He added that information of venous thromboses was not available in this study and "perhaps some of the other antibodies might have stood out if we were able to analyze for different outcomes."

This study was supported by a Pfizer Aspire Award. Knight reports receiving research funding and consulting fees from Jazz Pharmaceuticals outside the submitted work.

JAMA Network Open. Published online April 4, 2023. Full text.

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