Pacemakers make life better for many people with heart problems, but in some patients, they put so much strain on the heart that they actually trigger heart failure symptoms.
Electrophysiologists and medical-device makers have known the phenomenon for years. It even has a name — pacemaker-induced cardiomyopathy — a condition that will eventually affect thousands of the 200,000 Americans who will get a pacemaker to stimulate the right ventricle this year.
The realization that traditional pacing can trigger new heart problems has fueled a long-simmering debate in the cardiac-medicine community about the best place inside the heart to attach the pacemaker's wire.
An increasingly vocal group of doctors believes that a clever but somewhat challenging technique called "His bundle pacing" may hold the answer for how to pace the heart's right ventricle without placing the strain on the left ventricle that leads to pacer-induced heart failures.
Using this alternate method creates a more natural heart beat and is also cheaper than the most common way to treat pacer-induced problems, which is with a more expensive machine and more wires.
"It's to save patients and their families from the specter of heart failure," said retired Medtronic engineer Terry Williams, whose home office is festooned with patent plaques including for two His bundle pacing devices still sold by Medtronic today. "Also, heart failure is expensive and we don't need that burden in this country. And more importantly they don't need that burden in developing countries. They can't afford to deal with it."
About 100 heart doctors around the U.S. — including a handful in Minnesota — are trained to use a standard pacemaker to stimulate a nontraditional place in the heart near a structure called the His bundle, which is named for Swiss cardiologist Wilhelm His Jr. (1863-1934).
At the annual Heart Rhythm Society meeting this month in Chicago, proponents of His bundle pacing said educational sessions about the technique attracted capacity crowds, with proponents tweeting the hashtag #DontDisTheHis.
One of the modern-day pioneers of the technique, Pennsylvania's Dr. Pugazhendhi Vijayaraman, presented the first study of five-year outcomes from His bundle pacing at the meeting. The paper showed rates of death and heart-failure hospitalization lower for His bundle patients compared to traditional right-ventricular lead placement.
"If everyone was putting in His bundle pacemakers, we would dramatically reduce the amount of pacemaker-induced cardiomyopathy," said Dr. John Mandrola, an electrophysiologist in Louisville, Ky., who was not part of the study. "The icing on the cake is, the [wire] we use has been approved for a decade … and is hooked up to a standard pacemaker, so it is extremely cost-efficient."
The basic premise of His bundle pacing is simple: Attaching the tip of the pacemaker wire to a different part of the heart than normal can enable a more natural heartbeat, which is healthier in the long run.
Traditional pacing in the right ventricle delivers a single electric pulse that causes both right and left ventricles to contract, but the signal has to pass through muscle tissue on the right to get to the left ventricle, elongating the heart beat process by critical milliseconds and forcing the left ventricle to work harder to stay in the optimal rhythm with the right. That extra work can lead to less efficient blood pumping and regurgitation of blood through the mitral valve.
"Ventricular desynchronization caused by right ventricular apical pacing … may increase the risk of heart failure and [atrial fibrillation], particularly when imposed on the failing left ventricle," concluded a seminal 2003 paper in the journal Circulation on the so-called MOST trial, using the word "apical" to refer to the bottom apex of the right ventricle.
MOST produced the first strong association between apical pacing and heart failure. Since then, large-scale retrospective studies have pegged the rate of pacemaker-induced cardiomyopathies between 12 percent and 15 percent. A 2015 paper by Vijayraman found 15 percent of traditionally paced patients had been hospitalized for heart failure after two years, compared to 2 percent of the His bundle patients.
"When we do His bundle pacing, we are restoring the natural beat and optimal timing. That's why I think this is going to help a lot of patients," Vijayaraman said.
The His bundle is a key component of the heart's natural electric system, which is composed of high-conduction-velocity cells that to activate a precisely choreographed set of contractions that make the heart beat efficiently.
Vijayaraman's five-year outcomes data, presented at the meeting this month, show that His bundle patients treated in 2011 had a 27 percent chance of dying or going to the hospital for heart failure five years after surgery, vs. a 41 percent chance in a similarly sized group of patients treated at the same time at Geisinger Health System in central Pennsylvania with pacemakers wired in the normal way.
The difference was most pronounced among patients whose pacemakers were used most often.
For the physician, one drawback of His bundle pacing is that it requires learning how to implant a pacemaker lead with millimeter-level precision at an unusual location inside the heart. And the implant procedure doesn't always work: Only 80 percent of the 95 attempted His bundle patients in the Geisinger data had successful implantations.
The procedure may also require more time in the operating room, even though the compensation is the same, which is unlikely to please hospital administrators.
Nor is enthusiasm emanating from the device companies. The specialized medical devices needed for His bundle pacing — including a slender lead that attaches to the heart and a thin medical tube that guides the wire to the correct spot in the heart — is only sold by one company, Medtronic.
"I'm not sure how popular it will be," said Dr. David Steinhaus, medical director of cardiac rhythm and heart failure at Medtronic. "If we can reproduce the exact normal conduction system of the heart, you may ultimately have better function of the heart in the long term. So it's kind of an exciting an idea. Implementation is somewhat more difficult."
Heart-device competitor Boston Scientific Corp. sponsored a feasibility study of His bundle pacing in 2011, but has no plans to offer new devices specifically intended for the procedure. A spokeswoman noted that His bundle pacing "is associated with higher energy requirements from the pacemaker compared to conventional approaches," which makes the company's long-lasting Enduralife batteries well-suited for the therapy.
Observers note that His bundle pacing reduces potential need for a therapy called cardiac resynchronization therapy (CRT), which requires a sophisticated and costly device that paces the right and left ventricles with separate wires.
"His Bundle pacing is going to have to be physician-directed and investigator-directed. It's not going to be something that industry pushes on us," Mandrola said.
Dr. Henri Roukoz, an electrophysiologist at the University of Minnesota, uses His bundle pacing selectively in cases where he feels that patient anatomy and other factors make it a worthwhile risk.
"I think it's very promising, but it needs more research to ascertain its utility," Roukoz said. "It's still not a mainstay. But it's probably on its way."
Joe Carlson • 612-673-4779
