Additionally, the Micra Accelerometer Sensor Sub-Study (MASS) is being conducted at 4 centers already active in the Micra study in Austria, Spain, Hungary and France. Forty (40) subjects were enrolled in the Sub-Study, and enrollment in the Sub-Study was complete as of March 31, 2016. The purpose of the Sub-Study is to test feasibility for future enhancements in the Micra device functionalities.