Leadless Pacemakers and the Medtronic Micra AV: What Patients Need to Know
When a patient hears the word pacemaker, the picture in their head is usually the same one I had in medical school. A small metal box under the skin below the collarbone, with thin wires snaking down through a vein into the heart. That is a traditional transvenous pacemaker, and it has worked extremely well for decades. But it has real downsides. The pocket can get infected. The wires can fracture. The shoulder area gets a permanent bump. For some patients, particularly older adults with fragile veins or those with a history of device infection, the traditional design carries enough risk that we look for another option.
Over the last decade, that other option has become a reality. Leadless pacemakers are tiny self-contained devices that sit entirely inside the heart, with no wires and no chest pocket. The most widely used in the United States is the Medtronic Micra AV and its newer second-generation version, the Micra AV2. This article walks through how these devices work, who is a good candidate, what the procedure is like, and what the long-term outlook looks like.
What a Leadless Pacemaker Actually Is
A leadless pacemaker is a complete pacing system packaged into a single capsule about the size of a large vitamin. The Micra AV measures roughly 26 millimeters in length and 6.7 millimeters in diameter, weighs about two grams, and contains the battery, the pulse generator, the sensing electronics, and the pacing electrode all in one piece. There are no wires, no separate generator under the skin, and no chest incision.
The device is delivered through a small catheter inserted in the femoral vein at the top of the thigh. Under fluoroscopic guidance, the cardiologist navigates the catheter up the inferior vena cava, through the right atrium, across the tricuspid valve, and into the right ventricle. Small tines on the front of the device anchor it to the inner wall of the ventricular muscle. Once positioned and tested, the catheter is withdrawn, leaving the pacemaker in place.
The whole procedure is typically completed in under an hour. Most patients go home the same day or after a single overnight observation, with only a small puncture site at the groin to recover from rather than a chest incision.
How the Micra AV Senses the Atrium Without Wires
Standard pacemakers come in single-chamber versions that pace one chamber and dual-chamber versions that pace both the atrium and the ventricle while keeping them coordinated. The original Micra was a single-chamber device that paced only the right ventricle. That worked well for patients with permanent atrial fibrillation but was suboptimal for patients with normal atrial rhythm and AV block, because the heart loses the natural timing between atrial and ventricular contraction.
The Micra AV solved this problem in a clever way. It contains an internal three-axis accelerometer that detects the mechanical motion of the right atrium contracting. By recognizing the atrial kick from inside the ventricle, the device can fire a paced beat in the ventricle that follows naturally from each atrial contraction. This is called VDD pacing, and it restores AV synchrony without ever placing a wire in the atrium.
In the MARVEL 2 study, the algorithm achieved roughly 89 percent atrioventricular synchrony at rest in patients with complete AV block and normal sinus rhythm. The Micra AV2, approved by the FDA in 2023, refined this further with better synchrony at higher heart rates and longer battery life, while keeping the same size and overall design.
Who Is a Good Candidate for a Leadless Pacemaker
Leadless pacemakers are not for everyone. They occupy a specific clinical niche, and choosing the right patient is one of the most important parts of the decision.
The classic candidate for a Micra AV or Micra AV2 has one of these clinical situations:
- High-degree AV block that requires permanent pacing, where ventricular pacing dominates the device burden.
- Symptomatic bradycardia in the setting of atrial fibrillation, where atrial pacing is not needed.
- A history of cardiac device infection or pocket complication, where avoiding a chest pocket reduces re-infection risk.
- Limited or hostile vascular access in the upper body, including occluded subclavian veins, dialysis access, or prior vein damage.
- Frailty, advanced age, or chronic kidney disease where minimizing surgical exposure matters.
- Inability to lie still for or tolerate a longer transvenous procedure.
Patients who are typically not candidates include those with a mechanical tricuspid valve replacement, an inferior vena cava filter that blocks femoral access, severe femoral vein disease, or anatomy that makes safe device placement impossible. Patients who need full dual-chamber pacing with consistent atrial pacing, such as those with sinus node dysfunction in normal sinus rhythm, are usually still better served by a traditional dual-chamber pacemaker or by the newer Aveir DR dual-device leadless system from Abbott, which uses two communicating leadless devices, one in the atrium and one in the ventricle.
The Benefits Compared with Traditional Pacemakers
The advantages of going leadless are concrete and patient-facing. There is no chest incision and no subcutaneous pocket, which means no visible bump, no pocket hematoma risk, and no shoulder restriction during recovery. Patients can usually return to most normal activities within a few days, and there are no lifting restrictions for the affected arm because no arm is involved.
The infection profile is the most striking difference. Traditional pacemakers carry a small but real risk of pocket infection or lead-related endocarditis, both of which can be dangerous and often require complete system removal. In the Micra Post-Approval Registry and the multi-year follow-up data, there have been essentially no device-related infections requiring removal. This matters most for patients who have already had one device infection, who carry a substantially higher re-infection risk with another transvenous system.
Lead-related complications also disappear because there are no leads. Lead fracture, insulation breach, and venous obstruction simply cannot happen with a leadless device. Five-year data from the Micra registry show a major complication rate of about 4.5 percent, which compares favorably with the roughly 8.5 percent rate seen with transvenous systems at three years.
Battery Life and What Happens When It Runs Out
Battery longevity used to be one of the main concerns with leadless devices because the battery is small. Real-world data have been reassuring. The Micra has a manufacturer-projected battery life of about 12 years, and large registry analyses now estimate median expected longevity in the range of 14 to 17 years in clinical practice, depending on pacing burden and programming. The Micra AV2 was designed specifically to extend battery life further than the original Micra AV, particularly at higher pacing rates.
When the battery does eventually deplete, the device is typically left in place and a new leadless pacemaker is implanted alongside it in a different region of the right ventricle. Studies have shown that two and even three Micra devices can coexist in the right ventricle without interfering with each other or with cardiac function. For patients who started with a leadless device in their seventies or eighties, this often means the original device will outlast their need for replacement entirely.
The Aveir leadless system, by contrast, was designed with a dedicated retrieval system that allows the device to be physically removed at end of life. Both approaches are being used in practice, and the choice is part of the broader conversation between patient and electrophysiologist.
What the Procedure Looks Like
From the patient's perspective, a leadless pacemaker implant is similar to a cardiac catheterization. You arrive fasting in the morning. An IV is started, and you receive light sedation rather than general anesthesia in most cases. The skin at the upper thigh is numbed, and a small puncture is made in the femoral vein. The delivery catheter is advanced under fluoroscopy to the right ventricle, the device is deployed and tested, and the catheter is withdrawn. A pressure dressing is placed at the groin.
After a few hours of bedrest to ensure the femoral access site is sealed, most patients are walking and ready for discharge. Many go home the same day. The post-procedure restrictions are short. Patients are asked to avoid heavy lifting and strenuous lower-body exertion for a few days to protect the femoral access site, but there are no upper-body restrictions and no need to keep an arm in a sling.
Risks Worth Discussing
No procedure is without risk. The risks specific to leadless pacemaker implantation include cardiac perforation, which is uncommon but can cause pericardial effusion or tamponade and may require pericardial drainage or surgery. Femoral access complications such as bleeding, hematoma, or vascular injury occur in a small percentage of cases. Device dislodgement is rare with current Micra devices because the tines anchor securely to the trabeculated ventricular wall.
Rates of these complications have come down substantially as operator experience and device design have matured. The five-year Micra data show that the bulk of complications occur during or shortly after the implant, with very few late events. For most appropriately selected patients, the risk-benefit calculation favors leadless over transvenous, especially when infection risk or vascular access is a concern.
How I Discuss This Decision in Clinic
When a patient comes to me needing a permanent pacemaker, the first questions are not about the device. They are about the rhythm. Do they need only ventricular pacing or do they need atrial pacing too? Are they in permanent atrial fibrillation? How active are they? Is there any history of infection or vascular problems?
For a patient with permanent atrial fibrillation who needs rate-control pacing or for a patient with high-degree AV block who is in normal sinus rhythm, the Micra AV or Micra AV2 is often a strong first choice. For a younger active patient with isolated sinus node dysfunction, a traditional dual-chamber pacemaker or the Aveir DR may be more appropriate. For a patient with a recent device infection or hostile upper-body venous access, a leadless device often becomes the preferred option even when the rhythm picture would otherwise favor a dual-chamber system.
This is a decision I make jointly with the patient, the electrophysiologist who will perform the implant, and often with the primary care doctor who knows the patient's broader health picture. The conversation is detailed because the device, once implanted, is in place for many years.
The Bottom Line
Leadless pacemakers represent one of the most meaningful technical advances in pacing in the last fifty years. The Medtronic Micra AV and Micra AV2 give us a way to provide reliable ventricular and AV-synchronized pacing in a self-contained capsule that lives entirely inside the heart, with no wires and no chest pocket. For the right patient, this means a faster, less invasive procedure, a much lower risk of infection, and a recovery that is measured in days rather than weeks. The technology is not a universal replacement for traditional pacemakers, but it has earned its place as a first-line option for many patients I see in clinic.
Frequently Asked Questions
Will I be able to feel the leadless pacemaker?
No. Because the device sits inside the right ventricle and there is no pocket under the skin, there is nothing to feel from the outside. Patients cannot see or touch the device, and there is no visible bump on the chest.
Can I have an MRI with a Micra device?
Yes. Both the Micra AV and Micra AV2 are MRI-conditional, meaning MRI scans can be performed safely under specific conditions. You will need to inform the MRI technologist that you have the device so they can use the appropriate protocol.
Do leadless pacemakers have all the features of traditional pacemakers?
Most of the rate-responsive and pacing features are present, including AV synchrony in the case of the Micra AV. Single-leadless devices do not provide atrial pacing, which is a limitation for patients with sinus node dysfunction. Dual-chamber leadless systems like the Aveir DR address that gap.
How long does the battery last?
The manufacturer projects about 12 years of battery life, and registry data suggest median real-world longevity in the 14 to 17 year range depending on how often the device paces. For most older patients, the battery will not need replacement during their lifetime.
What happens when the battery does run out?
For Micra devices, the standard approach is to leave the depleted device in place and implant a new leadless pacemaker alongside it in a different part of the right ventricle. Studies have shown this is safe and effective. Aveir devices are designed to be retrieved at end of life using a dedicated snare system.
Is the procedure painful?
Most patients describe minimal discomfort. Light sedation is used during the procedure, and the only real soreness afterward is at the small femoral puncture site. There is no chest incision and no shoulder pain.
Can I exercise after a leadless pacemaker?
Yes, and usually sooner than after a traditional pacemaker. Lower-body activity should be limited for the first few days to allow the femoral site to heal, but there are no arm or shoulder restrictions and no long-term activity limitations once recovery is complete.
How do I know if I am a candidate?
The decision involves your rhythm pattern, your vascular access, your overall health, and your personal preferences. A discussion with your cardiologist and an electrophysiologist who implants both leadless and traditional pacemakers will sort out which option fits your situation best.
References
1. Steinwender C, et al. Atrioventricular Synchronous Pacing Using a Leadless Ventricular Pacemaker: Results From the MARVEL 2 Study. JACC Clin Electrophysiol. 2020.
2. El-Chami MF, et al. Leadless pacemakers at 5-year follow-up: the Micra transcatheter pacing system post-approval registry. Eur Heart J. 2024.
3. Reynolds D, et al. A Leadless Intracardiac Transcatheter Pacing System. N Engl J Med. 2016.
4. Knops RE, et al. A Dual-Chamber Leadless Pacemaker (Aveir DR i2i Study). N Engl J Med. 2023.
5. Crossley GH, et al. Two-year outcomes of Micra AV leadless pacemakers in the Micra AV CED study. Heart Rhythm O2. 2024.
6. Garweg C, et al. Advancements in Leadless Pacemakers: What the Second-generation Micra AV2 Brings to Cardiac Care. touchREVIEWS in Cardiology and Vascular Medicine. 2024.
7. Medtronic Micra AV2 Leadless Pacemaker, Prescribing Information and Technical Manual.
8. Vamos M, et al. Leadless Micra pacemakers: Estimating long-term longevity. A real world data analysis. Int J Cardiol. 2025.