Although light has been used to noninvasively alter the excitability of cardiac tissue in vitro, researchers have now succeeded in using an optical pacemaker to stimulate an intact heart to contract in vivo (Jenkins MW et al. Nat Photonics. 2010;4:623-626).
A team led by scientists at Case Western Reserve University in Cleveland, using pulses of infrared laser light at low radiant exposures, were able to reliably pace quail embryo hearts to the laser's pulse frequency without detectable tissue damage.
Hampton T. Optical Pacemaker. JAMA. 2010;304(13):1432. doi:10.1001/jama.2010.1370