Heartburn: Faulty Valve

In some people, the sphincter between the stomach and esophagus doesn't work as well as it should. This allows acid to seep into the esophagus (called acid reflux), where it can cause pain and irritation. Not everyone with acid reflux suffers from heartburn, and some people with "heartburn" symptoms don't actually have acid reflux but may have some other condition causing this pain.source by http://www.webmd.com/