乌鸦传媒

NEW ORLEANS -- Women with a history of postural orthostatic tachycardia syndrome (POTS) showed signs of improvement when treated with active stimulation of the vagus nerve using a device that clips onto the ear, a randomized clinical trial showed.

Postural tachycardia in the absence of a blood pressure drop was significantly less in the active arm compared to the sham arm at 2 months, with a change in heart rate of 18 bpm upon standing in the active arm compared with 32 bpm in the sham arm (P=0.016), reported Stavros Stavrakis, MD, PhD, of the University of Oklahoma Health Sciences Center in Oklahoma City.

That brought many patients below the commonly used threshold used to define POTS, an increase in heart rate of at least 30 bpm on assuming an upright position in the absence of orthostatic hypotension.

In his late-breaker presentation at the annual meeting of the Heart Rhythm Society, Stavrakis also reported that anti-autonomic antibodies were lower in the active arm compared to the sham group at 2 months (P<0.05). "We also saw a trend toward improvement in heart rate variability, which is a surrogate for autonomic tone, among those receiving active treatment," Stavrakis reported.

In commenting on the study, Fred Kusumoto, MD, of the Mayo Clinic in Jacksonville, Florida, and immediate past president of the Heart Rhythm Society, called vagus nerve stimulation an "exciting non-pharmacologic strategy" for a very difficult to treat condition without satisfactory treatment options.

Stavrakis agreed: "There have been many pharmacological and non-pharmacological therapies that have been tried, but the efficacy is not so good and often we have to try different combinations of therapeutic options. We definitely need novel therapeutic strategies for this."

POTS is a clinically heterogeneous disorder of orthostatic intolerance, characterized by a constellation of symptoms that last at least 6 months and include, but are not limited to, palpitations, mental clouding, nausea, fatigue, and dyspnea, after assuming an upright position, Stavrakis said. Stavrakis estimated the prevalence of the disorder at 0.2% – 1% of the population. Young adults, predominantly females, most frequently experience POTS.

Autonomic modulation via non-invasive vagus nerve stimulation has successfully been used in other conditions such as atrial fibrillation, he explained.

The device used in the study clips onto the ear and delivers electrical stimulation transcutaneously to the auricular branch of the vagus nerve.

"This is a completely non-invasive device," Stavrakis told 乌鸦传媒. "We stimulate it for 1 hour a day. There is a memory effect that lasts at least a few days, maybe some weeks, but it requires repeated use for long-term effect."

"We envision this as something like an ear pod that connects to a smart phone and delivers stimulation without anyone knowing what is going on. Everyone walks around with ear pods now anyway," he added.

After animal studies in the laboratory, Stavrakis and colleagues moved on to a clinical study involving 26 women, the predominant population with POTS. The study is a first-in-human, randomized sham-controlled clinical trial of transcutaneous vagus nerve stimulation in patients with POTS over a 2-month period.

The researchers assigned 14 women to receive the sham treatment and 12 women to the active stimulation. The average age of the women was 30 years, and all of them were taking at least one medication prescribed for POTS. "Adherence to the clinical appointments for use of the device was very good – better than 80% in both arms," Stavrakis said. "There were no crossovers during the trial, and no change in medical therapy. No device-related adverse events were observed."

Although the study was limited by its size, he said, "It sets the stage for a new therapy in this vexing clinical condition. We are excited about these results, and we are planning for the next stage which would be a multicenter clinical trial."

Kusumoto praised the sham-controlled design of the trial as adding to the value of the data by minimizing the placebo effect.

"This is proof of concept, and if it ultimately proves successful you can imagine there is a whole host of ways to make this easier for patients in the long term," Kusumoto told 乌鸦传媒. "We really know very little about POTS, and it is really a heterogeneous group of patients."

Correction: The original version of this article stated that the device attaches to the earlobe, it clips onto the tragus.

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