Patent ductus arteriosus is a congenital heart disorder where the ductus arteriosus, a blood vessel connecting the pulmonary artery and aorta, fails to close after birth as it normally would. This allows blood to shunt from the aorta to the pulmonary artery, potentially causing heart failure. It can be diagnosed via echocardiogram, electrocardiogram, or chest x-ray and may be treated with medications like indomethacin or surgery.