A German team of scientists have successfully tested an implantable vagal nerve stimulator that can control blood pressure, a new form of treatment that can potentially cure resistant hypertension or high blood pressure that fail to respond to medications.
More than a third of all adults in the world have high blood pressure, defined as systolic blood pressure equal to or above 140 mm Hg and/or diastolic blood pressure equal to or more than 90 mm Hg. If left untreated, it can lead to stroke, heart disease and kidney failure, which are some of the leading causes of disability and death globally, including the Middle East and North Africa (MENA).
Some 30 percent of those who suffer from this condition have resistant hypertension, an extreme type of high blood pressure that fail to respond to at least three anti-hypertensive medications and lifestyle modifications. Medications do not work for these people, and even if they do, they have adverse side effects like dizziness and fatigue.
German scientists are hoping that their nerve stimulator implant can be a safer yet effective alternative to anti-hypertensive drugs for people with resistant hypertension.
“An implantable device would allow reducing the blood pressure in these patients, either alone or in combination with the already applied medication,” Dennis Plachta, a microsystems engineer at the University of Freiburg in Germany, and leader of the study about the device, said in a statement. “It offers a second chance not available yet, and it can run in a tandem solution to a pharmaceutical treatment.”
The technique using vagal nerve stimulation (VNS) has been used for intractable epilepsy since 1998, and the German researchers explored how to use VNS for controlling blood pressure.
As described in the study published in the Institute of Physics (IOP) Journal of Neural Engineering, the device is a 20-millimeter-long, 0.8-millimeter in diameter, micromachined cuff that wraps around the vagus nerve in the neck. It has 24 individual electrodes that are selective enough to tap only the fibers that control blood pressure, but not those responsible for heart rate and breathing, avoiding unintended effects like bradypnea and bradycardia. The sensors deliver 40 pulses per second to the selected fibers.
The electrodes detect when blood vessels constrict as what happens when blood pressure spikes, and the device sends electrical signals to the brain to lower the blood pressure. In the experiment using rats, the implant was able to reduce blood pressure by as much as 40 percent with minimal side effects. The researchers are confident that they can replicate similar results during future human trials after adjusting for nerve stimulation patterns, electrode designs, and algorithms.
Implanting the device only requires a small incision to the left side of the neck. The device is connected to a small pulse generator implanted under the chest muscle.
Plachta and his team are working on an enhanced version of the nerve stimulator that can control blood pressure “on-demand” by continuously adjusting BP depending on physical activity. With real-time, optimal control, the implant could be a huge improvement over medication effects that waxes and wanes, which make the patient uncomfortable.
“The long-term goal is to provide ‘treatment-on-demand’ for the patient, whereby the implantable device uses an intelligent circuit to record the activity of the patient, for instance when they are doing exercise, and adjust the blood pressure accordingly,” Plachta said in a report by the Daily Mail.
Other researchers have also been tapping the body’s natural blood pressure system to control hypertension. The Rheos device developed by Keck School of Medicine of the University of South California is a pacemaker-like device that attaches to the left and right carotid arteries and sends signals to the brain to lower blood pressure.
Nerve implants bring hope to people who have tried but failed to control their blood pressure despite multiple medications, including many in the Middle East, where risk factors like obesity, sedentary lifestyle, increased stress, and high-fat and high-caloric diets are contributing to the already high prevalence of hypertension.
