Next in Heart Pacemakers: 'Look, No Leads!'

Kara Reamer's pacemaker didn't like her. At 36, she suffered from a condition called swallow syncope. As she ate, the act of swallowing affected her vagus nerve, causing a drop in her heart rate that made her faint. As a result, Reamer, a medical transcriptionist in Washington, West Virginia, had a two-lead pacemaker implanted at a hospital. That was six years ago.

From the beginning, it was one problem after another. A surgical complication had Reamer hospitalized with a chest tube. After she went home, issues with the pacemaker's timing left her drained and exhausted until the settings were readjusted.

A few years later, new symptoms cropped up. Certain activities, even vacuuming, affected her badly. "My face would turn red and it would swell," she says. "I'd get short of breath, and I would just have to wait for the blood to get back where it was supposed to be."

Reamer went to the Cleveland Clinic for evaluation. The vein containing her pacemaker leads had collapsed, she says. A year later, symptoms returned.

Now what? As it happened, Cleveland Clinic was part of a clinical trial for a new type of miniature, self-contained pacemaker. With no lead wires or crossover vein involved, the device is implanted directly into the heart. Reamer became a potential candidate.

Potential for Some

If leadless pacemakers are approved by the Food and Drug Administration, only certain patients with electrical disorders will become eligible -- those who just need stimulation of one chamber of the heart.

Pacemakers from two manufacturers are moving forward in U.S. clinical trials. The Nanostim leadless device, from St. Jude Medical, is less than a tenth of the size of a traditional pacemaker. The Micra leadless device, from Medtronic, is even smaller.

Dr. Daniel Cantillon, a specialist in cardiac electrophysiology at the Cleveland Clinic, is one of the lead investigators for the Nanostim clinical trial, funded by manufacturer St. Jude Medical. He was the third author of the latest study on the device, published in the Sept. 17 issue of the New England Journal of Medicine.

Latest Findings

Overall, in the 56-center Nanostim study, more than 90 percent of the patients had good short-term results, with their pacemakers working effectively. The study found a nearly 7 percent rate of serious adverse device events. Seven patients had their devices removed, which was managed without surgery.

The device is approved for use in Europe. The early course there was bumpy, with the company temporarily halting implants in early 2014 following several heart perforations related to procedures, with two deaths. Since then, improvements have led to better safety data.

Through the course of the U.S. study, best practices have been developed for implantation, operator training and patient-selection criteria.

Leadless Difference

Traditional pacemakers are surgically implanted in a "pocket" beneath the surface of the chest and connected to the heart by leads placed within a vein in the shoulder. The two main components are the pulse generator -- the electronics and lithium battery -- and one or more lead wires.

In contrast, the self-contained, leadless pacemaker attaches directly to the heart. The risk of lead breakage, dislodgment or infection is eliminated. Vein blockage is not an issue.

Leadless pacemakers are inserted without a surgical incision, so there's no scar. Instead, the entire device is threaded up into the heart in a catheterization procedure. The device is invisible except by X-ray, with no telltale bulge in the patient's chest.

With shorter, less-invasive procedures, patients recover more quickly. Expected battery life is longer for the new pacemakers, with a predicted span of about 15 years, compared with seven to 10 years for traditional pacemakers.

Smallest Ever

At slightly more than one-quarter of an inch wide and about 1 inch long, and weighing in at 2 grams (0.07 ounces), Medtronic's Micra is the smallest pacemaker to date.

An early performance trial of the Micra, reported in the October issue of the European Heart Journal, concluded the device can be safely and effectively applied. The Medtronic-funded study involved 23 centers in 11 countries. Pacemakers were implanted in 140 patients and assessed for safety, with 60 patients followed to assess three-month effectiveness.

"The technology is a result of not only advanced electronics but advanced miniaturization," says Dr. Ken Ellenbogen, an electrophysiologist and chairman of the division of cardiology at the Virginia Commonwealth University School of Medicine. "Instead of having a wire and then a battery with electronics, everything is on that tiny little capsule."

Ellenbogen, who is also chairman of the data and safety monitoring board for the pacemaker, says at present, 90 to 95 percent of the new Medtronic pacemakers are being implanted in patients with arrhythmias such as atrial flutter or atrial fibrillation.

Not for Everyone

One expert says while leadless technology represents an advance, a significant impact in the next few years is unlikely. "The major difficulty with this new technology is that in its current form, it can only pace the ventricle -- the bottom part of the heart," says Dr. Thomas Crawford, an assistant professor of medicine at the University of Michigan and an editor of CardioSource for the American College of Cardiology.

If it eventually became possible to implant a second capsule in the heart's upper chamber, the atrium -- with the ability to synchronize the two impulses -- many more patients would become candidates for leadless devices, Crawford says.

He says patients considering the device should ask: How easy would it be to extract it from the body after long-term, chronic use, when tissue may have grown around it?

There's little doubt the single-chamber devices will receive FDA approval within a year or so, Crawford says. "At the most, the manufacturers may be asked to provide additional safety data," he says, which might mean conducting another study with an additional 200 to 400 patients.

Symptom-Free

In April 2014, Reamer received the leadless pacemaker. "We went with it, and it's the best decision I ever made," she says.

Cantillon was part of Reamer's three-pronged procedure team. "What we did, which was pretty amazing, is actually remove, using laser tools, the traditional wires from the veins," he says. "And one of my colleagues had performed an angioplasty to open up the veins to restore normal blood flow from her upper extremities into her heart." Finally, Cantillon placed the new leadless pacemaker. As a clinical trial participant, Reamer is followed closely. A year and half later, she remains symptom-free.

Reamer is happy with the new pacemaker's appearance, or lack of. With her previous pacemaker, "the bump was very noticeable," she says. "And if I would run my hand down my collarbone, I could feel the wires." At the gym, she's no longer nervous when lifting weights and stretching her upper chest.

She was eager to speak out about taking part in the study. "I don't want people to not have the experience of this because it's new," she says. "I don't want them to be so afraid of it they don't do it."

Lisa Esposito is a Patient Advice reporter at U.S. News. You can follow her on Twitter, connect with her on LinkedIn or email her at lesposito@usnews.com.