A method for determining whether a medical device is appropriate for implanting into a cardiovascular conduit of a patient is disclosed comprising imaging a first section of the conduit of the patient into which the medical device is to be implanted during a first expanded state occurring at a first portion of a heart rhythm; reimaging the first section of the conduit of the patient during a first contracted state occurring at a second portion of the heart rhythm; deriving, from the imaging and the reimaging, dimensional characteristics of the first section of the conduit; and determining whether the medical device is appropriate for implantation in the first section of conduit based on the derived dimensional characteristics. The first section of the conduit includes a sizing device providing a selected radial force on the patient.