Infographic by Stephen Rountree

How the laser pacemaker works: 1) A microprocessor in an embedded catheter listens to the heart. 2) If it picks up an irregular heartbeat, an LED sends a signal to the pacemaker to fire its laser. 3) The energy from the laser is converted to electricity via electrodes that stimulate the heart.

If you have a pacemaker monitoring your heart, you’d better hope nothing goes wrong with your mind. That’s because MRIs–the most effective way to image the brain–and pacemakers don’t mix. The former heats the device’s implanted metal wires so much they could scar the heart or trigger a rapid heartbeat. Now, Wilson Greatbatch, inventor of the pacemaker, has teamed with Biophan Technologies to create a fiber-optic cable impervious to the MRI’s magnetic waves. Instead of using electricity directly, it jolts the heart with laser energy converted to an electric charge. The device should enter clinical trials in two years.

> Edited by Suzanne Kantra Kirschner with Jenny Everett