US Patent 9020611 Leadless cardiac pacemaker with anti-unscrewing feature

A leadless cardiac pacemaker comprises a housing, a plurality of electrodes coupled to an outer surface of the housing, and a pulse delivery system hermetically contained within the housing and electrically coupled to the electrode plurality, the pulse delivery system configured for sourcing energy internal to the housing, generating and delivering electrical pulses to the electrode plurality. The pacemaker further comprises an anti-unscrewing feature disposed on either a fixation device of the pacemaker or on the housing itself. The anti-unscrewing feature can be configured to prevent the fixation device from disengaging the wall of the heart.