Miniature Leadless Cardiac Pacemaker Performance | Journal Scan

Study Questions:

What is the early performance of Micra, a novel self-contained miniaturized pacemaker?


One hundred forty patients with pacing indications underwent implantation of a Micra leadless pacemaker in 23 centers.


Average age was 77; 61% were male. The indication for pacing was atrioventricular block (66%) or sinus node dysfunction (29%). There were no unanticipated serious adverse device events during the follow-up of 1.9 ± 1.8 months. Thirty adverse events related to the system or procedure occurred, primarily due to transient arrhythmias or femoral access complications. Eighteen patients developed pericardial effusion without tamponade. Only 60 patients were followed to 3 months, and mean pacing threshold was small, meeting the efficacy endpoint.


The authors concluded that the Micra transcatheter system is safe and effective.


Medtronic’s Micra transcatheter pacing system is a miniaturized single-chamber pacemaker system that is delivered via catheter through the femoral vein (27 French outer diameter) and implanted inside the right ventricle. The pacemaker is 25.9 mm in length, with an outer diameter of 6.7 mm. The pacemaker is capable of rate-responsive pacing and automated pacing capture threshold management. Recent advances in high-density batteries and low-power electronics allowed the creation of the leadless pacemaker, which eliminates the need for a device pocket and insertion of a pacing lead, thereby eliminating an important source of complications associated with traditional pacing systems. The main limitation, shared by its older St. Jude cousin (Namostim), is single-chamber pacing capability. The rate of acute complications was quite high. Hopefully, by the time this study ends the expected enrollment of 720 patients, the operators will learn how to avoid most of them. Long-term data on device performance will be closely anticipated.

Clinical Topics: Arrhythmias and Clinical EP, Pericardial Disease, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Arrhythmias, Cardiac, Atrioventricular Block, Femoral Vein, Follow-Up Studies, Heart Ventricles, Miniaturization, Pacemaker, Artificial, Pericardial Effusion, Sick Sinus Syndrome, Sinoatrial Node

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