John, a 47-year-old veteran officer and experienced bomb technician, was about to have a bad day, though no one, including him, saw it coming. The cool spring air made bomb suits more comfortable than usual, but after 14 minutes in the suits, it was time for the team to take a break. As his teammates started removing his helmet, John’s heart fibrillated and the blood stopped flowing to his brain. His struggle to maintain consciousness lasted only a few seconds, and he quickly collapsed and fell forward. He had no pulse—he was clinically dead. This officer had just become one of the more than 400,000 people each year who experience sudden cardiac arrests as the very first (and, tragically, often the very last) manifestation of undiagnosed heart disease.¹