The purpose of this glossary is to help guide those reading and researching in the area of adult congenital heart disease. It is meant to be a living document, constantly under revision, improvement, correction, as you, its users, find ways to ease the path for those who follow. To this end, if you cannot find a term you think should be here or if you see a way to improve the glossary, drop us an e-mail before you move on. We promise to consider all feedback carefully, and to make additions and revisions often.