Although it is possible that the Superior Vena Cava (SVC) syndrome (obstruction of blood flow through the SVC) was caused by the PDA ligation, this is a rare complication. The more common cause is
blood clots from central venous lines, or special IVs
that reach the deep veins near the heart such as the SVC. Anytime there is a foreign body such as an IV in the blood stream, there is a risk for clot formation.