An intracorporeal autonomous active medical device having a capsule body and a base. The capsule body includes a body portion and a lid portion, and the capsule body contains therein electronic circuitry containing the active elements of the autonomous medical device, and a power supply. The capsule body also includes a fastening system on an exterior surface of the capsule body that is configured to correspond with a fastening mechanism on the base configured to be anchored to a tissue wall. The fastening mechanism provides selective engagement between the capsule body and the base.
