We present the case of a 68-year-old man with a peculiar coincidence of cardiac pathologic findings: a huge left atrial myxoma, mitral insufficiency, a high degree atrioventricular block and three-vessel disease. The myxoma was vascularized from a dilated sinus arteriosus branch, giving rise to neovascularization at the base of the tumor. Blood from the neovascularization gathered into a large cavern which fistulated into the left atrium, responsible for a left-to-left cardiac shunt.