“It’s like being electrocuted,” said Alana, her body quivering. “It keeps happening. Doctors can’t tell me why.”

The 25-year-old had been walking with a friend on a sidewalk when everything started spinning and her body shook. Her chest tightened and she couldn’t breathe. Her friend called an ambulance, which brought her to the emergency room.

Dizzying, heart-thumping experiences like this one had been happening to her every few weeks for eight months. Brain scans showed nothing amiss. A specialist had found no inner ear problem. Her neurologist suspected arrhythmia (or irregular heartbeat), but she hadn’t seen a cardiologist yet to have it checked out.