(FORTUNE Small Business) – Every year 340,000 Americans die from sudden cardiac arrest, with about 80% collapsing at home, according to the American Heart Association. Automated external defibrillators (AEDs), which require no training to use and cost around $2,000, could save lives. But if you want an AED, you'll need a prescription—a leftover from the days when defibrillators were large, dangerous machines. That requirement is shackling a potential $800 million market for makers such as Cardiac Science, which produces 25% of all AEDs. Although the Irvine, Calif., company has annual sales of $62 million, it is still in the red. In July, AED giant Philips petitioned the FDA to lift the requirement; as of presstime, the decision was pending. —D.C.