Surgical Milestone: Philadelphia’s First Micra AV Pacemaker Implanted

The newly FDA-approved pacemaker is the world’s smallest pacemaker with atrioventricular (AV) synchrony, specifically designed for patients with AV block.

Dr. Arnold Greenspon, a cardiologist at Thomas Jefferson University Hospital, implanted the first Micra AV pacemaker on February 26, 2020, in Philadelphia. The newly FDA-approved pacemaker is the world’s smallest pacemaker with atrioventricular (AV) synchrony, specifically designed for patients with AV block.

We sat down with Dr. Greenspon, the director of the Cardiac Electrophysiology Laboratory at Jefferson Health, to find out what makes the Micra AV pacemaker different.

How have pacemakers changed over the past few decades?

Mirca pacemaker implanted in the heart

Micra and Micra AV implanted in the ventricle. Courtesy: Medtronic

The earliest pacemakers, around since the 1950s, required a surgeon to attach epicardial leads directly to the outside of the heart with a major surgical procedure. Transvenous leads, which pass through veins into the heart, were developed in the 1960s, making the procedure easier and safer. Today, implantation of a pacemaker involves the battery, or pulse generator, which could fit in a tablespoon, being surgically placed through a small incision under the skin in the upper chest.

The most recent innovation with pacemakers has been the development of a leadless pacing system, which attaches directly to the heart muscle to stimulate it and is controlled through wireless programming. The advantage of this system is that it doesn’t require a surgical incision or transvenous leads. It can be implanted in a heart catheterization lab with local anesthesia and minimal sedation.

What is a dual-chamber pacemaker and why is it important?

With a dual-chamber pacemaker, leads are placed in the upper and lower chambers of the heart, allowing it to pace both chambers while also sensing and tracking the rate of the upper chamber. These pacemakers attempt to simulate normal physiology with the ability to increase or decrease the pacing rate according to the patient’s activity level.

If you have AV block, it means that impulses aren’t being communicated between the upper and lower chambers of the heart. If you put a pacemaker just in the lower chamber it would not sense the upper chamber activity to coordinate cardiac contraction, called AV synchrony, or increase the pacing rate based on demand due to increased activity level. A dual-chamber pacemaker promotes AV synchrony and is responsive to a needed increase in heart rate.

What makes the Micra AV pacemaker different?

The original Micra pacemaker only paces the lower chamber of the heart. The Micra AV pacemaker implements new technology that allows it to sense the upper chamber’s change in blood flow due to an increase in rate. While placed on the lower chamber of the heart, it measures the same sounds that you can hear with a stethoscope to track the rate of the upper chamber. This technology allows us to treat more patients with a leadless pacemaker, providing AV synchrony and rate responsiveness without the need for additional leads.

Are there any complications or side effects?

Complications for leadless pacemakers happen much less frequently than those with a lead, which can result in infections or bleeding from surgical implantation and indwelling hardware. There can be some local complications when inserting the Micra AV pacemaker, but overall it’s a very low-risk procedure. Patients won’t notice the pacemaker once it’s implanted. It’s working in the heart and they won’t even know that it’s there.

Who is a candidate to receive the Micra AV pacemaker?

The ideal candidate is one who is older, has AV block and also may have other diseases or health conditions that would make them more prone to infection. A leadless pacemaker is lower risk, but it can’t be replaced once it’s put in place. The lifespan for the device is about eight to 12 years.

The invention and FDA approval of this pacemaker marks a great step in cardiac pacing technology. We’re able to help more patients with AV block, improving their quality of life without subjecting them to the risks of a standard pacing system.

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