A device (24) for placing a seal around an implant in a blood circulation passage is provided. The device includes a hollow sheath having a longitudinal axis, and at least one releaser, deployable relative to the sheath is provided. The device (24) includes, for the or each releaser, a sealing body (64) releasably fastened on that releaser, the sealing body (64) having an angular span smaller than 360° around the longitudinal axis, and a filiform link (67) connecting at least one releaser to another releaser and/or to the controller (68) positioned in the sheath, the filiform link (67) being deformable between a relaxed idle configuration and a stretched configuration limiting the radial movement of the sealing bodies (64).