The Micra is a leadless pacemaker, meaning it sits entirely inside the heart without any wires or a visible chest pocket. Made by Medtronic, it measures just 25.9 mm long and 2.8 mm in diameter, roughly the size of a large vitamin capsule. That makes it a fraction of the size of a traditional pacemaker, which typically includes a generator implanted under the skin near the collarbone and one or more wires (called leads) threaded through veins into the heart.
How It Differs From a Traditional Pacemaker
A conventional pacemaker is a two-part system: a pulse generator that sits in a small pocket created under the skin of your upper chest, and thin wires that run from the generator through a vein and into the heart. Those leads deliver electrical impulses that keep the heart beating at a normal rhythm. The system works well for most people, but the leads and the chest pocket are the most common sources of complications. Leads can fracture, shift, or develop infections over time, and the pocket itself can become infected or cause discomfort.
The Micra eliminates both of those vulnerabilities. The entire device, including the battery, electronics, and electrode, is a single self-contained capsule implanted directly inside the right ventricle. With no chest incision, no pocket, and no leads, you’re left with no visible bump under the skin and no scar on your chest.
How It Gets Into the Heart
The Micra is delivered through a catheter, a long flexible tube inserted into a large vein in the groin (the femoral vein). The catheter is guided up through the vein and into the right ventricle, where the device is released and attached to the heart wall using tiny flexible tines made of a nickel-titanium alloy. These tines grip the heart tissue securely without requiring screws. Once the device is positioned and tested, the catheter is withdrawn and the small puncture site in the groin is closed.
The entire procedure is typically done under sedation and takes about an hour. Because there’s no chest incision, recovery is faster than with a traditional pacemaker.
Recovery After Implantation
Most people feel some discomfort at the groin insertion site for the first 48 hours. You’ll need to keep the puncture site dry for about five days. Activity restrictions after a Micra implant are generally lighter than those for traditional pacemakers, since no chest pocket needs to heal and no leads need time to settle into position. With a traditional device, patients are typically told to avoid lifting more than 10 pounds on the affected side, skip golf, swimming, and tennis, and limit overhead arm movements for a full six weeks.
Your care team will give you specific guidelines, but many Micra patients return to normal daily activities within a few days rather than weeks.
Two Models for Different Needs
Medtronic makes two versions of the Micra, each designed for a different type of heart rhythm problem.
- Micra VR: Paces the right ventricle only. It’s designed for people who need simple, single-chamber pacing, such as those with a consistently slow heart rate that doesn’t speed up appropriately with activity.
- Micra AV: Also sits in the right ventricle, but uses a built-in sensor to detect the natural contraction of the upper chambers (the atria) and coordinate ventricular pacing accordingly. This makes it suitable for people with atrioventricular block, where the electrical signal between the upper and lower chambers is delayed or completely interrupted.
Battery life varies by model and how often the device needs to pace. Real-world data from a study of over 1,600 patients found median projected longevity of 16.7 years for the newer Micra VR2 and 15.6 years for the Micra AV2. The earlier-generation models had shorter projections: 12.3 years for the original VR and 10.8 years for the original AV.
Who Is a Candidate
The most common reasons anyone receives a pacemaker are sinus node dysfunction (where the heart’s natural pacemaker fires too slowly) and high-grade atrioventricular block (where the electrical signal between the heart’s upper and lower chambers is significantly delayed or blocked). Specific situations include a heart rate that drops low enough to cause fainting, dizziness, or fatigue, as well as complete heart block where the upper and lower chambers beat independently of each other.
The Micra is particularly well suited for people who are at higher risk for lead or pocket complications, including older adults, people on blood thinners, those with limited vein access, patients who’ve had previous device infections, or people on dialysis who need to preserve their arm veins. It’s not the right choice for everyone. People who need pacing in multiple heart chambers, such as those with heart failure requiring cardiac resynchronization therapy, need a more complex device with leads placed in different locations.
What Happens When the Battery Runs Out
When the Micra’s battery is eventually depleted, the device can either be retrieved through a catheter procedure or simply left in place (turned off) while a new Micra is implanted alongside it. Because the device is so small, at just 0.8 cubic centimeters, the heart can accommodate more than one. The decision to retrieve or leave the old device depends on how long it has been implanted and how much tissue has grown around it. Over time, the heart’s natural healing process encapsulates the device, making retrieval more complex.
MRI Compatibility
The Micra is classified as MRI conditional, meaning patients with the device can undergo MRI scans as long as specific conditions outlined by the manufacturer are followed. Before any MRI, both your cardiologist and the radiology team review the requirements for your particular model. The device has a dedicated MRI mode that allows it to continue pacing safely during the scan. This is an important practical advantage, since many people with pacemakers will need an MRI at some point in their lives for unrelated medical issues.
Potential Risks
No implanted device is without risk. The catheter delivery can, in rare cases, cause damage to the femoral vein, a blood clot, or a puncture of the heart wall (cardiac perforation). Because there are no leads or chest pocket, the Micra avoids the most frequent complications seen with traditional pacemakers: lead fractures, lead dislodgement, and pocket infections. Studies comparing the two approaches have consistently shown lower overall complication rates with leadless devices, largely because those lead and pocket problems simply cannot occur.
The tines that anchor the Micra to the heart wall can occasionally shift in the days after implantation, which may require a repositioning procedure. Your care team monitors the device remotely after implantation to catch any issues early.