An atrioventricular fistula is a fistula between an atrium and a ventricle of the heart. In medicine, a fistula (pl. ... In anatomy, the atrium (plural: atria) is the blood collection chamber of a heart. ... In anatomy, a ventricle is a part of the body filled with fluid. ... The heart and lungs (from an older edition of Grays Anatomy) The heart (Latin cor) is a hollow, muscular organ that pumps blood through the blood vessels by repeated, rhythmic contractions. ...