Leadless cardiac pacemakers (LPMs) are revolutionary new devices that are implanted directly into the heart without the use of transvenous leads. Traditional pacemakers require leads to be threaded through veins into the heart. These leads can fracture or dislodge over time, requiring additional procedures. LPMs solve this problem by containing the entire pacemaker mechanism within a small cylindrical device that is placed directly into the right ventricle via a catheter. This leadless design eliminates the risks associated with conventional pacing leads.
The First FDA-Approved LPM - Micra Transcatheter Pacing System
In 2016, the Medtronic Micra Transcatheter Pacing System became the first Leadless Pacemakers approved for use in the United States by the FDA. The Micra device is only 6mm in diameter and 26mm in length, less than 1/6 the size of traditional pacemakers. Similar to traditional dual-chamber pacemakers, the Micra senses and paces the right ventricle. However, it transmits information and receives programming commands wirelessly through a programmer placed on the skin over the implant site.
The approval of Micra was based on data from the global, prospective, nonrandomized Micra Transcatheter Pacing System Study. This study evaluated the safety and efficacy of Micra implantation in 1,000 patients across 60 centers worldwide. Results showed the device was effectively implanted via catheter with high rates of connectivity and appropriate sensing and pacing. Complication rates were also low.
Other Approved and Investigational LPM Systems
A few years after Micra's approval, the FDA approved a second LPM - Abbott's Nanostim leadless pacemaker. Several other LPMs are currently in development or undergoing clinical trials as well, including:
- Boston Scientific's Lotus valve - A combination LPM and aortic valve replacement device in a single catheter delivery system.
- Medtronic's Micra AV - An investigational LPM with AV synchronous pacing capabilities.
- MicroPort's Wilson Greatbatch LPM - A leadless dual-chamber device in early trials in China.
While these technologies are still new, long-term data will help determine how they can be further optimized to potentially replace traditional pacemakers for many patients. LPMs offer advantages over traditional pacemakers like avoiding lead complications. But further advances may be needed regarding battery life, programming interfaces, and dual-chamber capabilities.
Patient Selection
Patient selection is an important consideration for LPM implantation. Current guidelines indicate LPMs are reasonable options for:
- Patients requiring ventricular pacing who are at high risk for lead complications from traditional pacemakers. This includes those with tricuspid valve disease, repeated pacing lead fractures/dislodgments, or risks of leads infecting veins or the heart.
- Patients with temporary pacing needs who desire avoidance of transvenous leads. Some are using LPMs as "bridges" in these scenarios prior to traditional system implants.
- Patients with limited life expectancies who will not outlive the current LPM battery life estimates of 5-7 years.
However, LPMs are not suited for all pacemaker-dependent patients at this time. They are not approved for uses like His-bundle pacing that require more pacingcapabilities. And certain anatomical factors like calcified or very large heartsmay make catheter-based implantation more challenging. Careful pre-procedural screening helps ensure appropriate patient selection.
Implantation technique
Implanting a leadless pacemaker requires a minimally invasive cardiac catheterization procedure performed in an electrophysiology lab. Several key steps are involved:
1. Vascular access is obtained usually via the femoral vein. A long, thin delivery catheter containing the compressed LPM is guided to the right ventricle under fluoroscopy.
2. The LPM is slowly ejected from the catheter and self-expands to attach to the ventricular wall via small tines. Positioning is confirmed with imaging and electrical assessments.
3. The delivery catheter is uncoupled from the LPM and slowly withdrawn. This leaves just the small, self-contained device in place without any leads.
4. A programming wand placed on the skin over the implant site allows interrogation to ensure the LPM is sensing/pacing properly and to program therapy settings.
5. The vascular access site is closed, and the patient recovers. Most go home the same day after brief monitoring.
Follow-up involves periodic device interrogations and replacements once batteries deplete after 5-7 years. Long-term outcomes data are still emerging but complication and reintervention rates appear fairly low. Advancements continue to simplify the implantation process as well.
Future directions
While leadless pacing has made tremendous progress since the first human implant in 2010, continued innovation remains ongoing. Areas receiving focus include:
- Improving battery longevity - New energy sources could potentially double or triple current LPM battery life.
- Developing true dual-chamber and multi-site pacing capabilities - Overcoming challenges in coordinating sensing/pacing from two or more distributed LPM locations.
- Combination devices - Integrating LPM functions with other cardiac therapies like valves, annuloplasty rings, or even implantable defibrillators.
- Alternative implantation methods - Perhaps avoiding vascular access altogether via introduction through an incision in the chest.
As long-term clinical data accumulates, LPM technology aims to become a reliable leadless pacing platform offering advantages over traditional transvenous systems for suitable patients. With anticipated improvements in the pipeline, leadless pacemakers show promise for ongoing evolution of cardiovascular device therapy.
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About Author:
Priya Pandey is a dynamic and passionate editor with over three years of expertise in content editing and proofreading. Holding a bachelor's degree in biotechnology, Priya has a knack for making the content engaging. Her diverse portfolio includes editing documents across different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. Priya's meticulous attention to detail and commitment to excellence make her an invaluable asset in the world of content creation and refinement.
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