Failure of a child's DA (ductus arteriosus) to close after birth results in a condition called patent ductus arteriosus
and the generation of a left-to-right shunt. If left uncorrected, patency leads to pulmonary hypertension
and possibly congestive heart failure
and cardiac arrhythmias. I have not been through it personally, but I see lots of these a year and generally the surgeries go very well and recover to a normal life, with some exceptions.