This article explains it quite nicely. If I decide to take part in the study the first step involves a procedure to discover whether or not I do have a hole in my heart. And guess what? It involves shoving something down my throat. I'm so over having that kind of thing done. Unlike the endoscopy that I had a month or so ago, I'll be wide awake for this one :0( I'm going to talk it over with Number Guy and make a decision about it this week.