Think of all the things you know that lasers can do now add one more to the list. A team of biomedical engineers has successfully used a laser to control the beating of embryonic hearts. The study appears in Nature Photonics this week, and suggests that optical pacing is not only more effective than other forms of cardiac pacing, but also causes significantly less damage to the heart tissue.

The researchers used a pulsed infrared diode laser and a multimode fiber to stimulate 25 embryonic quail hearts, as well as a laser Doppler velocimeter to monitor the embryos' heart rates. Before being paced with the laser, the average interval between the heartbeats was 1.58 seconds; after laser stimulation at 2Hz (for the less mathematically inclined, that’s a rate of two cycles per second), the average interval between heartbeats was 0.4996 seconds, which matched the pulse rate of the laser nearly perfectly.

Traditional electrical pacing of the heart can cause serious tissue damage, but laser stimulation caused minimal harm to the embryonic tissue. The researchers used transmission electron microscopy to determine whether various heart components, such as the cardiomyocytes (specialized heart muscle cells), were damaged. Compared to control embryos that were not paced, there was no significant damage to embryos subjected to laser pacing.

While the results clearly indicate that lasers are capable of controlling heartbeats, the mechanism behind this phenomenon isn’t completely clear. The researchers hypothesize that the temperature gradient created by the laser pulses affects the action potentials that create the electrical signal that controls the heartbeat. This could lead to an altered rhythm, but further research needs to be done to determine how, exactly, optical pacing works.

The successful use of lasers in heart pacing has great potential, both for noninvasive mechanical studies of the heart and for possible clinical applications, such as a new type of pacemaker.

Nature Photonics, 2010. DOI: 10.1038/NPHOTON.2010.166 (About DOIs).