Leadless Pacemaker for Patients with AV Block

Feb 08, 2022 at 08:05 pm by steve

Amit Shah, MD

"I'm a huge fan. It's revolutionary," says Amit Shah, MD, about leadless pacemakers. Shah, who is a clinical cardiac electrophysiologist with Cardiology Consultants, has deployed approximately 200 of these devices in the last three years, with about 80 of them being the newest version by Medtronic, called Micra AV, approved by the FDA in February 2020.

"Now with the Micra AV, any patient with heart block--which is the majority of the patients for pacemakers--is a candidate for a leadless pacemaker. It has really opened the door in terms of patients who would benefit from it," Shah says.

The original Micra Transcatheter Pacing System (TPS), now called Micra VR, is predominantly for patients afflicted with atrial fibrillation (AFib). Implanted directly into the right ventricle, the world's smallest pacemaker delivers electrical impulses that pace the heart through an electrode at the end of the device.

The Micra AV serves to synchronize. The device doesn't pace the atrium, but it does adjust pacing in the ventricle to coordinate with the atrium. "It's a detection device to help keep the atrium and ventricles synchronized with each other," Shah says. "As long as the patient's atrial activity is normal, this is a wonderful device."

The two leadless options cannot yet pace the atrium. Only the traditional pacemaker can pace and synchronize the four chambers. "Down the road, we're hoping for leadless atrial pacing and even leadless left ventricular pacing, which will be a game changer," Shah says.

The two leadless pacemakers match in all but one thing. "Everything about them is identical, their implant technique, their profile," Shah says. "It's just a software difference and one little sensor. But with that little sensor, the Micra AV gives us the ability to detect the atrium and get atrial synchrony."

About two-thirds of Shah's patients who would have previously needed a traditional pacing device now end up as candidates for the leadless option. "It's changed my practice," he says.

Slightly larger than a big vitamin capsule, but with short, flexible prongs at one end, the Micra pacemakers are guided through a small slit in the thigh via a catheter up the inferior vena cava and through the right atrium of the heart into the right ventricle where it is deployed. "It's on a tether, so you can control it," Shah says. "When you're comfortable that it's well adhered in the right place, we cut the tether and remove the whole system."

The patient gets one stitch. "Usually within four to six hours, they're up and walking and can go home," Shah says, "but most patients generally stay overnight, because patients needing pacemakers usually have comorbidities or have traveled too far to return that day."

The whole procedure takes about 10 minutes. It takes around 45 minutes to insert a traditional pacemaker, which also requires a two-inch incision to develop a pocket under the skin below the collarbone where the device rests. Then with the traditional, the leads are fed through a vein down into the appropriate chambers of the heart where the device syncs either or both the atria and ventricles.

Because of the leads and the pocket, the traditional pacemaker also comes with additional risks, such as infections, lead displacement, and thrombosis. Patients of leadless devices not only avoid those risks, but also avoid immobilization requirements after the procedure. Traditional pacemakers patients must keep their left arm in a sling for one to three weeks to prevent the leads from shifting. "That sling is a problem for patients who use canes and walkers, or have issues from strokes," Shah says.

Cosmetically, the Micra pacemakers also leave no mark. Being completely inside the heart, they leave no bump under the skin and no scar, like devices. "Literally no one knows you have it, which the younger patients are excited about," Shah says.

The leadless pacemakers are still an evolving new technology, and having been introduced only five years ago, some patients and providers may be reticent or unfamiliar with them. "There are still a lot of people who either don't feel comfortable with them, don't have experience with them, or don't have access to them," Shah says.

Not surprisingly, traditional pacemakers are also changing. "There are advancements in traditional pacing coming out that make us wonder whether going back to traditional pacing may have some advantages because of where you can put the wire," Shah says. "This is an exciting time in pacing. In the past 40 years, the only evolution had been in devising smaller devices and batteries. There hasn't been a major advancement in pacing technology until the past few years with leadless and induction pacing. Now instead of having just one tool, we have multiple options, which is very, very exciting."

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