Continuous murmurs

• Patent ductus arteriosus. PDA is an abnormal connection between the aorta and the pulmonary artery, which normally should be closed in infancy. Since aortic pressure is higher than pulmonary pressure, a continuous murmur occurs. This murmur is often described as a machinery murmur, or Gibson's murmur. This is named for George Alexander Gibson, who characterized it in 1898.
• Aortopulmonary window.
• shunts. Usually a left to right shunt through a small atrial septal defect in the presence of mitral valve obstruction.