Collective term for congenital open connections (shunts) between the heart chambers, atria and/or between the vessels of the pulmonary arteries and the aorta. Normally, the pulmonary circulation is separate from the systemic circulation. If holes are left in the ventricular or atrial septum (ventricular or atrial septal defect) during embryonic development of the heart, there is a short-circuit connection, oxygen-poor (right) and oxygen-rich (left) blood can mix. The normally open connection between the pulmonary artery and the aorta closes after birth. If this remains open, blood flows from the aorta (left) back into the pulmonary artery (right) and this is called an open ductus Botalli with left-right shunt. Depending on the direction of blood flow and the pressure ratio, a left-right or right-left shunt develops.
