The purpose of this clinical study is to evaluate the safety and efficacy of the Micra Transcatheter Pacing System and to assess long term performance.

The study is being conducted in 56 sites located around the world, including 30 sites in the United States (U.S.).

Up to 780 subjects were planned to be enrolled (i.e. consented) to allow up to 720 subjects to be implanted enabling at least 600 subjects to be followed for at least 12-months post-implant.

There are two primary objectives in this study (one safety and one efficacy). The primary safety objective of the study is to evaluate major complications related to the Micra system or procedure. The primary safety endpoint was pre-specified to be evaluated at 6-months (183 days) post-implant. The primary efficacy objective, Micra pacing capture thresholds, was also pre-specified to be evaluated six months post-implant. This study also has a separate long term safety objective that will provide additional long-term safety data following potential regulatory submissions.

All subjects will be followed until official study closure (official study closure is defined as when Medtronic and/or FDA requirements have been satisfied per the Clinical Investigational Plan and/or by a decision by Medtronic or regulatory authority).

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.

An algorithm was designed to sense the atrial contraction using the Micra accelerometer.

Inclusion Criteria:

• Subjects who have a Class I or II indication for implantation of a single chamber ventricular pacemaker according to ACC/AHA/HRS 2008 guidelines and any national guidelines
• Subjects who are able and willing to undergo the study requirements and are expected to be geographically stable for the duration of the follow-up.
• Subjects who are at least 18 years of age (or older, if required by local law).

Exclusion Criteria:

• Subjects who are entirely pacemaker dependent (escape rhythm <30 bpm). (Please note: Subjects who are entirely pacemaker dependent (escape rhythm <30 bpm) can now be included in the study. Medtronic notified all sites on July 23, 2014 that the restriction against pacemaker dependent subjects was lifted, following review of the Early Performance Assessment.)
• Subject has an existing or prior pacemaker, ICD or CRT device implant.
• Subject has unstable angina pectoris or has had an acute myocardial infarction (AMI) in the 30 days prior to eligibility assessment.
• Subjects with current implantation of neurostimulator or any other chronically implanted device which uses current in the body. Note that a temporary pacing wire is allowed.
• Subjects with a mechanical tricuspid valve, implanted vena cava filter, or left ventricular assist device (LVAD).
• Subjects who are morbidly obese and physician believes telemetry communication of ≤5 inches (12.7 cm) could not be obtained with programmer head.
• Subjects whose femoral venous anatomy is unable to accommodate a 23 French introducer sheath or implant on the right side of the heart (for example, due to obstructions or severe tortuosity) in the opinion of the implanter.
• Subjects who are considered as unable to tolerate an urgent sternotomy
• Subjects with a known intolerance to Nickel-Titanium (Nitinol) Alloy.
• Subjects for whom a single dose of 1.0mg dexamethasone acetate may be contraindicated.
• Subjects with a life expectancy of less than 12- months.
• Subjects who are currently enrolled or planning to participate in a potentially confounding drug or device trial during the course of this study. Coenrollment in concurrent trials is only allowed when document pre-approval is obtained from the Medtronic study manager.
• Pregnant women, or women of child bearing potential and who are not on a reliable form of birth control.
• Subjects with exclusion criteria required by local law (e.g. age, breast feeding, etc.).