Abstract: Apparatus and methods are provided for forming a working space on the interior wall of a blood vessel, such as the aorta. The working space is isolated from blood flow and permits creation of an anastomotic hole and subsequent suturing of the hole to form an end-to-side anastomosis, even while the heart is beating. The apparatus comprises tools including inflatable barriers, such as cup-shaped balloons, which engage the inner wall of the blood vessel with minimum trauma and maximum sealing. In a first embodiment, the inflatable barrier is introduced through a penetration at the site of the anastomotic attachment. In a second embodiment, the inflatable barrier is introduced through a second penetration axially spaced-apart from the site of the anastomotic attachment.