A coronary fistula is a heart defect, usually present from birth, that is characterized by an improper junction of a coronary artery with a chamber of the heart or other blood vessel. It usually happens due to a malformation of a coronary artery that occurs during fetal development. Such a defect can also sometimes develop in a child or adult due to an infection, heart trauma or heart surgery. Babies with a coronary fistula may have an irregularly quick heartbeat or heart palpitations, rapid breathing, lethargy, growth delays and chest pain. Some fistulas are without symptoms and may close over time without medical treatment, but others will require either a minimally invasive catheter-based procedure or surgery to address the problem.