On September 14, 2007, Lorenz Diesbergen, age 44, stepped off a commuter train in downtown Chicago and began his daily walk to work in the Chicago Loop. As he crossed the bridge over the Chicago River, his heart’s normal rhythm suddenly deteriorated into an uncoordinated frenzy of useless fibrillations. He may have managed a few more steps—we don’t know—before he pitched forward and fell face-first onto the sidewalk. Paramedics were on the scene within minutes, but efforts at resuscitation proved futile. He left behind a wife and four children.