An implantable medical device (IMD) may include a fixation module, and a device module that is configured to be releasably connected to the fixation module. The device module may have a proximal end and a distal end, and may include a power source and a controller that is operably coupled to the power source. The controller may be configured to sense cardiac electrical activity via two or more electrodes and/or deliver pacing pulses via two or more electrodes. The device module may include a first part of a releasable connector while the fixation module may include a second part of the releasable connector, wherein the first part of the releasable connector and the second part of the releasable connector cooperate to releasably connect the device module with the fixation module.
