An arteriovenous fistula is defined as the communication between one coronary artery with a vein or to a cardiac cavity. The fistula is localized in the right coronary artery (55% of cases) or in the left coronary artery (35% of cases). It seems that the connections between the coronary system and a cardiac cavity are due to the persistence of embryonic sinusoids and intratrabecular spaces. Most of these fistulae drain into the right ventricle, the right atrium or to the coronary sinus. Occasionally, fistulae between the coronary and pulmonary arteries are found during a coronary angiography.