The device comprises an internal support upper arm and an external support lower arm, designed to work together so that, by gripping, the upper arm and the lower arm push against an internal face and an external face, respectively, of the lateral vessel wall; a tightening arm which rotates around an axis between an unlocked and a locked position in which the tightening arm pushes against the lateral wall and works with one of the two lower and upper arms to pin the lateral wall against at least one of the arms; and movement means designed to manually shifted between an open and closed position and to rotate the tightening arm when moving from an open to a closed position. In addition, provision is made of anti-return means, separate from the movement means, for blocking the rotation of the tightening arm in the opposite direction from the tightening direction when said tightening arm is in the locked position.