Health Problem: Bradycardia due to atrioventricular (AV) dysfunction or sinus node dysfunction may result in hemodynamic consequences. A permanent cardiac pacemaker (PM) is the definitive treatment for symptomatic bradycardia that is not caused by underlying disorders or medication. More than 600,000 PMs are implanted annually worldwide, with > 250,000 implanted in the United States each year. However, overall, traditional transvenous pacing systems (TVPMs) have a 10% complication rate, including lead- and pocket-related events. The transvenous leads are the most common source of complications, removal, and revision surgery.

Technology Description: The Micra Transcatheter Pacing System (TPS) is a single-chamber right ventricular pacing device. The device senses electrical activity of the heart via electrodes within the titanium capsule. Heart rhythm is monitored for bradycardia. Rate-adaptive pacing therapy is provided based on programmed pacing parameters. The Micra TPS is self-contained and does not require a surgical incision in the chest or intravascular leads. It is inserted via 23Fr catheter placed in the femoral vein and held in place within the right ventricle of the heart via nitinol tines that attach to the myocardium.

Controversy: Leadless PMs have become an attractive option in an attempt to avoid complications associated with the transvenous leads in traditional TVPMs. However, the leadless cardiac pacemekers are presently limited to single-chamber ventricle placement, which comprise a minority (< 10%) of all PMs. Compatibility with other implanted devices such neurostimulators is unknown at present. The battery life of the Micra TPS has been estimated at 12 years, although longitudinal empirical evidence is needed. In addition, the Micra TPS is implanted in the myocardium; more experience with percutaneous retrieval over long timeframes is indicated.

Key Questions:

  • Is the Micra TPS effective in treating symptomatic paroxysmal or permanent high-grade AV block in the presence or absence of atrial fibrillation, symptomatic bradycardia-tachycardia syndrome, or sinus node dysfunction?

  • How does the Micra TPS compare with TVPMs or other leadless cardiac pacemakers?

  • Is the the Micra TPS safe?

  • Have definitive patient selection criteria been identified for the Micra TPS?

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