This report describes an unreported complication after stent-grafting of the aortic arch for residual dissection following ascending aorta and aortic arch replacement for acute type A dissection. The patient developed, one year later, a pseudoaneurysm originating from the proximal suture line and therefore far from the stent-graft landing zone, that fistulized into the pulmonary artery. Possible causes are: suture damage during stent deployment or change of system forces after stent placement leading to high-tension on the suture line. Emergency surgery was performed. Aortic arch stent grafting is a new promising technique but its complications are still not completely known.