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Viral illness may spur ‘standing up’ disorder

Mar. 13, 2014, 10:04 AM

Circulating “autoantibodies” possibly triggered by a viral illness may contribute an abnormally rapid heart rate or tachycardia upon standing that affects 500,000 Americans, mostly young women, according to researchers at the University of Oklahoma and Vanderbilt University.

Their findings, published Feb. 26 by the Journal of the American Heart Association, could lead to new treatments for the condition, called postural tachycardia syndrome, or POTS.

Symptoms also include shortness of breath and weakness upon standing, and exercise “intolerance” that have lasted for at least six months.

Satish Raj, M.D., MSCI

“The cause of POTS is probably multifactorial, with different underlying causes in different patients” said co-author Satish Raj, M.D., MSCI, associate professor of Medicine and Pharmacology at Vanderbilt and consultant at the Vanderbilt Autonomic Dysfunction Center. In some patients, however, symptoms occur after a “viral-type” illness, he said.

In the current study, researchers evaluated blood samples from patients with POTS and also from healthy individuals. They found evidence of antibodies in blood samples from patients that bind to receptors on cells regulating vascular tone and to other receptors on cells involved in the regulation of heart rate.

“Our research found autoantibodies caused changes that altered cell function,” said senior author David Kem, M.D., George Lynn Cross Research Professor of Medicine at the University of Oklahoma Health Sciences Center and a member of its Heart Rhythm Institute.

“These autoantibodies interfere with normal changes in the system that control the ability of blood vessels to become narrower and prevent the expected drop of blood pressure as the patient stands,” Kem said.

The body compensates for this by increasing sympathetic nerve activity, which helps maintain blood pressure but directly speeds up the heart rate.

“We’re just at the beginning of a series of studies to try to understand what this means in terms of its potential for impacting the patient care in the clinic,” Raj said.

“This opens up a new avenue of investigations, both to better characterize and understand the cause, and potentially to look at different treatments.”

Luis Okamoto, M.D., research instructor in Medicine at Vanderbilt, also contributed to the research. National Institutes of Health grants supporting the Vanderbilt research included HL102387, NS065736 and TR000445.

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