Medtronic Micra – Worlds Smallest Cardiac Pacemaker

Medtronic Micra – Worlds Smallest Cardiac Pacemaker

Medtronic Micra - Worlds Smallest Cardiac Pacemaker
The new Medtronic Micra (right) compared to
a conventional single chamber pacemaker.
When the St Jude Nanostim received CE approval, you could guarantee that soon there would be other leadless Pacemakers soon on the market. The next in the pipeline appears to be the Medtronic Micra TPS (Transcatheter Pacing System). At one tenth of the size of a conventional pacemaker it is the worlds smallest cardiac pacemaker but is yet to receive CE like its competitor.

Leadless Pacemakers

Leadless pacemakers look to reduce some of the risks associated with conventional pacemakers by removing the need for a pacemaker ‘pocket’ or leads. Traditionally pacemakers sit in a ‘pocket’ just under the skin in a persons chest with one or more leads running down directly into the heart. This carries an increased risk of infection or lead displacement, both of which are common complications of pacemaker implants. The leadless pacemaker is deployed within the heart secured by small tines (think grapple hook). Electrical impulses are received and/or delivered using a small electrode at the base of the device that is held in place directly in contact with the interior surface of the heart muscle.  

Implantation of the Medtronic Micra (TM) 

The devices are implanted using a long catheter (hollow wire) that is passed into the heart via the femoral vein (big blood vessel in the leg). The benefit of this is that implant procedures themselves will be less invasive and should also be quicker.

St Jude Nanostim Vs Medtronic Micra

As it stands there is no comparison to be made, with only the Nanostim having CE approval there is only one available leadless pacemaker on the European market. The time for comparison will not be until both devices are available on the common market and have years of implant data under their belts. CE or FDA approval for the Micra (TM) should not be too far away though. On the 9th of December 2013, Medtronic announced the worlds first implant of their Micra (TM) and the start of the devices medical trial. The trial of the Micra (TM) is to include up to 780 implants in 50 centres. The 3 month follow up data of the first 60 patients to receive the devices is due to be released in the second half of 2014 and hopefully CE approval will follow shortly afterwards. 

Limitations of Leadless Pacemakers

Both the Micra (TM) and the Nanostim (TM) are only able to sense and pace in one chamber. As a result, their position in the market is as VVI devices – simple pacemakers that at the very best are considered in the following populations;
  • Chronic Atrial Fibrillation with 2 or 3° AV Block or bifascicular bundle branch block (BBB) 
  • Normal sinus rhythm with 2 or 3° AV or BBB block and a low level of physical activity
  • Patients with a short expected lifespan.
  • Sinus Bradycardia with infrequent pauses or unexplained syncope with EP findings.
This is a relatively small percentage of the pacemaker market between 10-15% 
As with anything new in medicine, there is a lack of long term data to say with any assurance that the devices will satisfy their obligation over a prolonged period of time – this is not a criticism but a fact that is true of all medical advances. In time however I am confident that these devices will help their niche market!

Further explanation around these topics and more is available in the book Pacemakers Made Easy by Carl Robinson.

For these reasons these devices are not yet the definitive answer but definitely a step in the right direction.
Time to go and check a conventional pacemaker!
Thanks for Reading
Cardiac Technician
Read more here Medtronic Micra

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