Implantable Electrode Cuff Lowers Blood Pressure

A prototype implantable cuff equipped with electrodes can help lower blood pressure (BP) without causing side effects.

The BaroLoop procedure developed by researchers at the University of Freiburg (Germany) takes advantage of the baroreflex homeostatic mechanism, which helps to maintain BP at nearly constant levels. It does so by using a special cuff with 24 electrodes that is implanted in the vagal nerve (VN). The device works by first determining which of the electrodes is closest to the nerve fibers that transmit the BP signal. It then uses electrostimulation to overwrite the information in these fibers with such precision that other nearby bundles of nerve fibers (with other functions) are not affected.


The novel method for selective VN stimulation is based on true tripolar recording and a coherent averaging algorithm triggered by BP or electrocardiogram. In in-vivo experiments in rats, tripolar stimulation over electrodes near the baroreflex fibers reduced BP without triggering significant bradycardia and bradypnea. The BP drop was adjusted to 60% of the initial value by varying the stimulation pulse width and duration, and lasted up to five times longer than the stimulation. The study describing the BaroLoop procedure was published on May 8, 2014, in the Journal of Neural Engineering.

“The presented method is robust to impedance changes, independent of the electrode's relative position, does not compromise the nerve, and can run on implantable, ultra-low power signal processors,” concluded lead author microsystems engineers Dennis Plachta, PhD, of the department of microsystems engineering (IMTEK), and colleagues.

The baroreflex provides a rapid negative feedback loop in which an elevated BP reflexively causes the heart rate to decrease, causing BP to decrease. Decreased BP lowers baroreflex activation and causes the heart rate to increase and to restore BP levels. The baroreflex can begin to act in less than the duration of a cardiac cycle (fractions of a second). The system relies on specialized stretch receptor neurons known as baroreceptors in the aortic arch, carotid sinuses, and elsewhere to monitor changes in BP and relay them to the brainstem, which then mediates BP by both branches of the autonomic nervous system, the parasympathetic and sympathetic nerves.

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