Phoebe Dow's debilitating stroke came out of the blue as the 19-year-old was working her regular shift as a waitress.

"I had no idea what was happening," she remembers. "All of a sudden…my right arm felt heavy and I couldn't lift it up, and my right leg, I couldn't move it." She was slurring her words. Her customers thought she was drunk. But at the hospital, doctors discovered a clot had reached her brain, causing a severe stroke.

The cause of Dow's stroke was a tiny hole between the two atria of her heart, present from birth. In about 25 percent of people, that hole fails to close completely. It generally causes no problems, but if a clot manages to sneak through the hole, it can go to the brain and cause a stroke, or to another area of the heart and cause a heart attack.

Phoebe was lucky, for two reasons. First, because she was so young, her brain was able to repair itself, and now, seven years later, she has recovered almost completely.

That's because she was enrolled in an experimental trial of a device called an Amplatzer PFO Occluder that actually closes that tiny hole in her heart. The procedure was done at Memorial Hermann-Texas Medical Center in Houston. The device is folded up inside a tube and threaded all the way from the groin to the heart. Once inside the heart, it opens like a tiny umbrella, two umbrellas in fact, sealing both sides of the hole.

A recent study found the device is more effective than the standard medication treatment for patients who have PFO and have already suffered one stroke. For Dow, it means she's no longer at high risk for a second stroke.