A cannula for connecting a medical device to a biological system is taught. The cannula includes a tissue engagement portion, preferably in the form of an annulus, to which a vacuum is applied through the cannula to attract and hold tissue of the biological system in an initial connection while an affixment device is applied to complete the connection. In addition to a working fluid conduit, comprising a main port, a working fluid passage and a working fluid port, and a port to apply the vacuum, the cannula can include a sensor port to allow sensing pressure or other characteristics of the working fluid at a point closely adjacent to the connection between the cannula and the biological system.