A stent graft (10, 50, 70) for deployment into the aorta of a patient has a tubular body (12, 76) with a proximal portion (14, 78) of a selected diameter； preferably a reduced diameter portion (16, 79), distal of the proximal portion, having a diameter less than the selected diameter； a tapered portion (18, 80) extending between the proximal portion (14, 78) and the reduced diameter portion (16)； and optionally a distal portion (20), distal of the reduced diameter portion (16, 79). Low profile side arms (26, 28, 30, 32, 42, 71-75) are provided, preferably in the reduced diameter portion (16, 79) and/or the tapered portion (18, 80). The side arms (26, 28, 30, 32, 42, 71-75) are for connection of an arm extension (81) to an aortic branch vessel. A paraplegia prevention vent tube (34, 40, 52) can be provided in fluid communication with the main lumen (11, 77), which opens to external of the tubular body (12, 76) in the region defined by the reduced diameter portion (16, 79) and the tapered portion (14, 79). The paraplegia prevention vent tube (34, 40, 52) is to provide temporary perfusion to external of the stent graft (10, 50, 70) after deployment of the stent graft (10, 50, 70) into the aorta, and is subsequently blocked. In some embodiments, at least three, preferably four or five, low profile side arms (71-75) are provided, all but one to be connected at the physician's choice and depending on the anatomy of the patient； and one to serve the function of the paraplegia prevention vent tube (34, 52).
