A hospital blackout. An urgent clinical need. Four weeks to create a device that could keep a heart beating.

In 1957, a power outage exposed a dangerous weakness in the pacemakers then used after heart surgery: they were bulky machines tethered to electrical outlets. University of Minnesota heart surgeon C. Walton Lillehei turned to Earl Bakken, an electrical engineer, University alumnus, and co-founder of the young Medtronic, with an urgent challenge: build a small, portable, battery-powered alternative.

Within four weeks, Bakken delivered. The resulting wearable pacemaker helped free cardiac pacing from the wall outlet, transformed patient care, and helped propel Medtronic from a small medical-equipment repair company toward a leading role in medical-device innovation.