From an interview with
Dr. Prabal Guha, Electrophysiologist
McLeod Cardiology Associates

Traditional implantable heart pacemakers were the size of a cigarette pack. Today, the Micra™ Pacemaker is only about the size of the end joint of your little finger, says McLeod Electrophysiologist Dr. Prabal Guha.

Here is a summary of Dr. Guha’s comments:
A regular pacemaker has two wires, one in the upper part of the heart and one in the lower part of the heart. It first makes the upper part fire and, then, the lower part fires. Or it sees that the upper part is firing and makes the lower part fire. Any pacemaker maintains a synchrony between the upper and lower chambers of the  heart.
 
The older, leadless pacemaker cannot see the heart’s upper part. It just keeps the lower part beating, regardless of how the upper part is working.

The new Mitra AV™ technology cannot drive the upper part, but it can sense the activity from the upper part. But, when it senses the activity from the top chamber of the heart, it can stimulate the lower part and maintain the synchrony between the upper and the lower parts. That is the newest advance in the technology for the leadless pacemakers.
 
The device is the Micra™. It’s a very small device, which can be implanted directly inside the heart. It does not require any wires or leads, because it is connected directly into the heart muscle.
 
The Micra™ senses the electrical activity from the heart. When it sees that the heart slows down or pauses, it gives an electrical pulse to get the heart going. It works exactly the same way as a regular pacemaker, except that it is very small and is implanted directly inside the heart.
 
Anybody who needs a pacemaker, may be a candidate for Micra™. However, we use it mainly for people without a good place to put the regular pacemaker or who do not have a good vascular access. These people are good candidates for the Micra™. Some patients, who only require intermittent pacing or pacing in one chamber of the heart, they may also benefit from the Micra™.
 
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