The device includes a body having the general shape of a cylinder so as to be engaged in a trocar that is introduced into the aortic duct, the body having, at one of its ends that is accessible from outside the trocar, a maneuvering member secured to a measuring means which is present at the other end of the body and which is able to be deployed diametrically under the effect of an action exerted on the maneuvering member in order to come into contact with the wall of the aortic valve.
