A stent graft (10) for deployment into the aorta of a patient has a tubular body (20) with a proximal portion (14) of a selected diameter and a portion (16) of a reduced diameter less than the selected diameter distal of the proximal portion and a tapered portion (18) extending between the proximal portion and the portion of reduced diameter. Low profile side arms (26, 28, 30, 32) are provided in the portion of reduced diameter and/or the tapered portion. The side arms are for connection of an arm extension to an aortic branch vessel. A paraplegia prevention vent tube (34) is provided in fluid communication with the main lumen and open to external of the tubular body in the region defined by the portion of reduced diameter and the tapered portion. The paraplegia prevention vent tube is not intended to be connected to a side branch of the aorta but to provide temporary perfusion to external of the stent graft after deployment of the stent graft into the aorta and intended to be subsequently blocked.
