Around 67 million American adults have high blood pressure, putting them at risk of heart attack or stroke. But researchers from Germany have developed an implantable device that they say can reduce blood pressure by delivering electrical signals to the brain.
The research team, led by Dr. Dennis Plachta of the University of Freiburg in Germany, recently published the first set of results from their creation in the Journal of Neural Engineering.
The device, which the researchers call the "multichannel cuff electrode" (MCE), is made up of 24 separate electrodes that are incorporated into a cuff designed to wrap around the vagal nerve.
The vagal nerve extends from the brain through the face and thorax to the abdomen, and activates and supplies major organs, such as the heart, and major blood vessels.
When blood vessels stretch, this activates signaling from baroreceptors - sensors that help regulate blood pressure (BP). The researchers explain that some of these baroreceptors congregate in the aortic arch and send signals to the brainstem through fibers in the vagal nerve.
Researchers say the implantable device could help patients with high blood pressure who are unable to use medication for the condition.
The MCE device works by identifying and stimulating the specific baroreceptor fibers in the vagal nerve that influence BP, while avoiding the fibers that are responsible for other major body functions, such as heart rate and ventilation.
Blood pressure in rats 'reduced by 40%'
To test the effectiveness of the device, the team used a prototype - 2 cm in length and 0.8 mm in diameter - on five male rats. The device sent 40 electrical pulses per second to the baroreceptor fibers of rats' vagal nerve.
The researchers tested a variety of sites on the vagal nerve and used the device for different durations and at different amplitudes and frequencies to determine an optimal stimulation method.
They found that BP in the rats was reduced by 40% through adjusting pulse width in combination with amplitude. When sites closest to the baroreceptor fibers were stimulated, no major side effects occurred.
Commenting on the findings, Dr. Plachta says:
"Our proof-of-concept interface has shown that it is possible to use the left vagal nerve to reduce blood pressure without any adverse side effects, which is important for a wide variety of potential treatments that could utilize nerve stimulation without actually penetrating the nerve."
According to the researchers, approximately 30% of patients with high BP do not respond to medical treatment.
Dr. Plachta says that implanting the device would require surgery, so it would not be used as primary treatment for patients with high BP. But he notes it would be useful for patients who are unable to use BP-lowering medication.
Speaking of the long-term plans for the device, Dr. Plachta says the goal is to give patients "treatment-on-demand," where the "implantable device uses an intelligent circuit to record the activity of the patient, for instance when they are doing exercise, and adjust the BP accordingly."
But for now, he says, the team plans to test the effectiveness of the device on larger animals, such as pigs and sheep.
Medical News Today recently reported on a study suggesting that children who spend more than 2 hours a day in front of a TV, computer or video games are at increased risk of developing high BP.