Billed as the world’s smallest pacemaker, Medtronic’s new Micra TPS (Transcatheter Pacing System) is about the size of a large vitamin capsule.
At about one-tenth the size of a regular pacemaker, which is about the size of a silver dollar, the one-inch device is small enough to be delivered through a catheter near the groin and implanted directly into the heart where it is attached with small, sharp prongs on the end of the device.
Pacemakers are surgically implanted devices that generate electrical impulses that correct irregular or stalled heart beats. A normal heart rate is about 60 beats per minute. Pacemakers monitor abnormal heart rates and generate electrical impulses that cause the heart to contract or beat normally in response to the patient’s activity level.
Dr. Sujoya Dey is a cardiac electrophysiology specialist, who specializes in the diagnosis and treatment of cardiac disease at Marin General Hospital. She said she has implanted “countless” pacemakers over the years but, “This is completely different.”
Aside from the size, one of the biggest advantages of the self-contained Micra TPS is that it has no wire leads. Instead, Dey said, it’s attached directly to the heart wall with the tiny prongs, which deliver electrical stimulation via an electrode on one end.
Nearly 1 million people worldwide are implanted with pacemakers each year, according to Medtronic, which has locations in Santa Rosa and all over the world. The Mira is manufactured in Minnesota.
According to Medtronic, there have been more than 10,000 Micra implants worldwide since its introduction.
The first external pacemaker was developed in the 1940s. The pulse generator was worn on the belt or strapped to the body with electrodes placed over the heart area.
Over the years they have undergone transformations, but for the last decade or so they have remained pretty much the same, Dey said.
The Micra device was introduced in 2013 and used in Europe before the FDA approved it for use in the U.S. in April 2016.
The Micra is not recommended for patients who are severely obese, or who have an intolerance to materials in the device or the blood thinner heparin. Patients also must have veins that are able to accommodate the size of the pacemaker.
The Micra is also a single-chamber pacing system. It paces only the right ventricle of the heart. As the heart has four chambers through which blood flows, patients who require dual-chamber pacing will still need to go with a traditional pacemaker.
A traditional pacemaker is implanted under the skin near the collarbone. Wire leads run from the pacemaker to the heart and provide an electrical connection between the pulse-generating device and the heart.
However, there can be complications with the leads which can sometimes malfunction, fray, break or wear out, requiring surgery.
The Micro lasts about the same amount of time as a regular pacemaker, seven to 10 years before the batteries die.
The procedure to implant the Micra also takes about the same amount of time to perform as the regular pacemaker, about 45 minutes.
But whereas a regular pacemaker is taken out and replaced, the Micra is left in the body, and another one is implanted.
“It gets enmeshed in the tissue,” Dey said.
People using the Micra, the same as those using traditional pacemakers, must follow some precautions. Medtronic recommends keeping items containing magnets at least 6 inches away from the implanted pacemaker. This includes cell phones, MP3 players, headphones and magnetic therapy products, as the energy can interfere with the electrical stimulation.
Pace of pacemaker change
The pacemaker dates back to the early 1940s. They were external devices to help regulate heart rhythm, but were large, bulky, relied on external electrodes and had to be plugged into a wall outlet. They could also fail during a power blackout.
In the mid-1950s, Dr. C. Walton Lillehei, a pioneer in open-heart surgery at the University of Minnesota Medical School, and his colleagues set out to develop a better system with the help of Medtronic engineers.
One of those was Earl Bakken, who developed a new kind of pacemaker that was not much larger than a paperback book. He used parts from electrical devices he had in the shop. The device’s circuitry was based on a design for a transistorized metronome he had seen in a trade publication.
The pacemaker was powered by mercury batteries, provided a 9-volt DC pulse, and could easily and comfortably be worn by young patients, according to Medtronic.
The original Bakken pacemaker was tested in the University of Minnesota’s laboratory, then applied to a pediatric heart patient. The device immediately restored the child’s heartbeat to near normal. Within days, the child’s heart resumed a normal rhythm on its own, and the pacemaker was removed.
In the U.S., the first implantable pacemaker was developed in 1960.