Cleveland, OH--A New Scientist story from Jeff Hecht reports that in addition to the known use of lasers to stimulate heart cells, a medical laser has now been used as a whole-heart pacemaker by a team at Case Western Reserve University. Millisecond-long pulses of infrared laser light with a wavelength of 1.87 microns were sent through an optical fiber towards the heart of a quail embryo. Before they switched on the laser, the heart beat once every 1.5 seconds, but firing the laser twice a second quickened the heartbeat to match the laser rate as long as the laser fired.
"It worked beautifully: the heart rate was in lockstep with the laser pulse rate," said Duco Jansen of Vanderbilt University in Nashville, TN, who collaborated with Andrew Rollins at Case on the experiments. The team saw no sign of laser damage after hours of experiments—although prepping the heart for the experiment involved opening the egg, which ultimately killed the embryo.
Jansen picked the 1.87 micron wavelength because water partly absorbs such light, warming cells but not cooking them. Somehow the temperature gradient triggers the changes in membrane potential that make the heart beat.
Early applications of the technique will be in studying the developing heart to illuminate cardiac disease—particularly in probing embryonic hearts that are too small to have electrodes inserted into them. "This is an alternative to electrical stimulation with higher spatial resolution," says Jansen. "And since we're stimulating in a domain different than the electrical domain in which we're recording data, it avoids interference."
He adds that better understanding of the excitation mechanisms will be critical in building devices for use in clinical applications, which could include optical pacemakers.
SOURCE:New Scientist; www.newscientist.com/article/dn19310-laser-sets-quail-embryos-hearts-racing.html?DCMP=OTC-rss&nsref=online-news
