A team at the University of Leeds used a standard TENS (Transcutaneous electrical nerve stimulation) machine like those designed to relieve labour pains to apply electrical pulses to the tragus, the small raised flap at the front of the ear immediately in front of the ear canal.
The stimulation changed the influence of the nervous system on the heart by reducing the nervous signals that can drive failing hearts too hard.
"You feel a bit of a tickling sensation in your ear when the TENS machine is on, but it is painless," said 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," Deuchars said.
Researchers applied electrodes to the ears of 34 healthy people and switched on the TENS machines for 15-minute sessions.
They monitored the variability of subjects' heartbeats and the activity of the part of the nervous system that drives the heart.
"The first positive effect we observed was increased variability in subjects' heartbeats. A healthy heart does not beat like a metronome," said lead researcher Dr Jennifer Clancy, of the University of Leeds' School of Biomedical Sciences.
"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. We found that when you stimulate this nerve you get about a 20 per cent increase in heart rate variability," Clancy said.
The second positive effect was in suppressing the sympathetic nervous system, which drives heart activity using adrenaline.
"We measured the nerve activity directly and found that it reduced by about 50 per cent when we stimulated the ear," Clancy said.
"This is important because if you have heart disease or heart failure, you tend to have increased sympathetic activity.
"This drives your heart to work hard, constricts your arteries and causes damage. 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," Clancy added.
The researchers found significant residual effects, with neither heart rate variability or sympathetic nerve activity returning to the baseline 15 minutes after the TENS machine had been switched off.