An optical pacemaker that uses pulses of infrared laser light to control the beat of an embryonic heart is reported online in Nature Photonics this week. Laser pulses have previously been shown to stimulate contractions in individual heart cells, but this is first time that a laser beam has been used to pace an entire heart in vivo.

Michael Jenkins, Andrew Rollins and colleagues used an optical fibre to deliver 1-2 millisecond-long pulses of infrared light to the hearts of 2-3-day-old quail embryos. They found that the heart beat became synchronized and 'locked' to the laser pulses, with the beat following the laser pulsing rate as it was increased from twice to three times a second and back again.

Once optimized, this all-optical approach could become a useful aid for cardiology, allowing for non-contact studies without need for the invasive electrodes usually employed. Experiments to assess the feasibility of the approach for pacing an adult heart, however, still need to be performed.