The ear could be the key to one's heart, researchers at the University of Leeds say, noting that stimulating the nerves in the ear could distract nervous signals that are overexerting a heart in poor health.
The research team conducted their experiments on 34 participants using a TENS (transcutaneous electrical nerve stimulation) machine, a medical instrument used to relieve labour pains.
"You feel a bit of a tickling sensation in your ear when the TENS machine is on, but it is painless," says Professor Jim Deuchars, Professor of Systems Neuroscience in the University of Leeds' Faculty of Biological Sciences.
"It is early days -- so far we have been testing this on healthy subjects -- but we think it does have potential to improve the health of the heart and might even become part of the treatment for heart failure."
Participants' heart rates were monitored during a 15-minute session connected to the TENS machine. Researchers continued to monitor them for another 15 minutes after the machine was turned off.
According to lead researcher Dr. Jennifer Clancy, the first encouraging result was an increased variability in participants' heart rates by 20 per cent.
"A healthy heart does not beat like a metronome," says Clancy. "It is continually interacting with its environment -- getting a little bit faster or a bit slower depending on the demands on it. An unhealthy heart is more like a machine constantly banging out the same beat."
The other positive effect of the TENS machine was the hindrance of adrenaline production in the sympathetic nervous system (SNS), another culprit of cardiac overstimulation.
Ear stimulation reduced SNS nerve activity by 50 per cent, according to Clancy, who notes that patients troubled by heart failure are typically plagued by an overactive SNS.
"This drives your heart to work hard, constricts your arteries and causes damage," says Clancy. "A lot of treatments for heart failure try to stop that sympathetic activity -- beta-blockers, for instance, block the action of the hormones that implement these signals. Using the TENS, we saw a reduction of the nervous activity itself."
The positive effects lasted throughout the entire 15 minutes of monitoring that occurred after the TENS machine had been turned off.
The method, say the researchers, targets a major nerve called the vagus which controls several major organs including the heart.
"We now need to understand how big and how lasting the residual effect on the heart is and whether this can help patients with heart problems, probably alongside their usual treatments," says Deuchars. "The next stage will be to conduct a pre-clinical study in heart failure patients."
The study was published in the journal Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation.
