In this paper, we interrogate the current views on medical expertise, and expertise more in general, by building upon the study of an innovative medical procedure called transcatheter aortic valve implantation (TAVI). We find that phenomena like TAVI require that we modify our traditional views of expertise to acknowledge its social, material and distributed nature. We also find that in the case of TAVI expertise feeds upon the broad circuits of knowledge created by the combination of professional relationships, social ties and, increasingly, economic interests. Becoming and remaining an expert implies not only being socialised in a local regime of activity but increasingly also participating in, learning to navigate, and exploiting alternative and potentially competing circuits of knowledge, which may be controlled by private companies. The case of TAVI helps us to appreciate expertise as a translocal and connected phenomenon and foreground some of the implications of the emergence of proprietary circuits of knowledge.