The technique is so precise that it could set the pace for even a single cell.
Laser beams can be used to control heart rate.
The laser heats the heart, opening an ion channel that causes heart tissue to contract.
Scientists hope this could lead to laser-based pacemakers for humans.
Laser beams could keep hearts beating on time, according to scientists from Case Western Reserve University and Vanderbilt University. The research could lead to more precise heart measurements as well as less invasive and less damaging laser-based pacemakers.
"When I electrically pace a heart, I just dump current into the heart, and it goes everywhere," said Michael Jenkins, a scientist at Case Western Reserve University and a co-author on the recent Nature Photonics paper.
"Here I can place my energy in a specific location at a specific time. It's so precise I could pace just a single cell," he added.
To achieve this result, scientists started with a quail egg. They cracked it open and extended a tiny fiber optic cable until the cable almost touched the developing heart. They then pumped millisecond-long pulses of light through the fiber and into the heart.
When the laser beam strikes the developing heart, it creates a temperature gradient: one side of the heart gets hot. The change in temperature opens an ion channel in the cell membrane. Charged particles then flow out through the channel, triggering a mild electrical impulse that causes the heart to contract.
The normal embryonic heart beats once about every 1.5 seconds. The laser-beam regulates heartbeat in lockstep with the twice-a-second laser pulse. When the lasers stopped firing, the heart rate returned to normal.
The laser pulses did not appear to damage the heart tissue. However, by cracking open the egg to insert the fiber-optic cable, the scientists killed the animal. Although the lasers killed birds in the lab, scientists hope their new technique could soon save human lives.
Laser-based pacemakers would be easier to implant and less prone to complications than their electrical counterparts. The metal-based electrodes of today's electrical pacemaker can damage or destroy heart cells.
Laser-based pacemakers would require also less energy. That should save more lives by reducing the risk of surgery if such devices are ever created and approved by the Food and Drug Administration.
However, that won't happen for years, said Jenkins. Even if the technology does become available to patients, laser-based pacemakers probably won't completely replace electricity based pacemakers.
The new research is only the latest in a string of laser-based implantable devices. Scientists at Northwestern University, including Claus-Peter Richter, have been studying laser-based cochlear implants for years.
"This is a field still in its infancy, but it's growing very rapidly," said Richter.
Compared with electrical stimulation, a laser beam offers much more precise control over a nerve, whether that nerve is in the heart, the ear, the eye or elsewhere. The specific laser wavelength and how that laser is used differs from tissue to tissue, but the general principle is the same.
The lasers are so precise that they can restore hearing to the deaf and could soon restore sight to the blind, touch to amputees, and, if used as a pacemaker, life to those with a broken heart.