Implantable cardiac pacemakers are helping to keep Masters swimmers going
This article appears in the September-October 2018 issue of SWIMMER.
Steven Reiss first noticed something wrong while swimming with his buddies at the New York Athletic Club in 2013. Reiss, a Manhattan trial attorney and veteran open water swimmer, had worked out with these guys for nine years. Together they’d completed, relay-style, five Manhattan Island Marathon Swims and an English Channel crossing.
A former marathon runner who’d switched to swimming after his knees gave out, Reiss was used to endurance exercise of all sorts. Usually, he thrived on it, but on that day, he became so winded after swimming three lengths of the pool that he had to stop to catch his breath. “This was really unusual for me,” he says. That afternoon, it happened again while climbing stairs to his office.
Fearing a heart problem, Reiss, in his early 60s at the time, saw a cardiologist, who checked his coronary arteries and pronounced them clean. He told Reiss his resting heart rate was in the 40s, low by most standards but more rule than exception in highly fit individuals. Bottom line: There was nothing wrong with the structure of Reiss’s heart.
Reassurance notwithstanding, Reiss’s episodic fatigue persisted. “I’m very sensitive to changes in my body,” he says, “and I knew something was wrong. So, I proceeded to go to different specialists, all of whom found some little thing in their specialty they thought might be the reason.” None of these, from allergies to thyroid problems, panned out.
After a year of frustration, Reiss’s general practitioner recommended an electrophysiologist, a specialist in heart rhythms. Before this appointment, Reiss, now 66, wore a portable Holter monitor to track his heart’s electrical system for 24 hours. Shortly after dropping off the device at the hospital, he received a call from cardiologist Stavros Mountantonakis, a member of Asphalt Green Masters.
“Dr. Mountantonakis said he wanted to know why I wasn’t in the emergency room,” Reiss recalls about this first encounter. The monitor confirmed Reiss’s low resting heart rate, but it also found a freakishly low ceiling on his maximum heart rate, which never climbed over 78 beats per minute regardless of activity level. Even scarier were the prolonged gaps between beats. At random times throughout the day and night, Reiss’s heart would stop beating altogether for four or five seconds at a time.
The question wasn’t why exercise exhausted Reiss. It was how could he exercise at all.
An Engineering Marvel
When operating optimally, the human heart is a marvel of mechanical, electrical, and chemical engineering—an indefatigable pump capable of instantly adjusting its rate and contractility to meet a body’s shifting demands for oxygen and nutrients. Exercise, emotional stress, even a come-hither look from a romantic crush: These are just a few of the things that can make our hearts quicken and pound.
Marching orders for such escalation initially come courtesy of electrical impulses speeding along nerve fibers in the so-called sympathetic nervous system. The message is then further turbocharged and sustained by fight-or-flight hormones such as adrenaline.
Once the excitement passes, adrenaline dissipates, and the brain sends a new set of signals via the vagus nerve, a key component of the “rest-and-digest” parasympathetic nervous system. These signals are vital to cardiac relaxation. Without them, researchers have found, an average person’s resting heart rate couldn’t dip below 100.
Endurance-trained athletes, to be sure, rarely have to worry about inadequate vagal functioning. Endurance training greatly enhances vagal tone, one reason why distance swimmers such as Reiss often have such low resting heart rates. The medical term for this is bradycardia, which sounds disturbing and can be, but rarely in highly fit people. “We often see athletes whose heart rates dip into their 30s or even 20s when they are asleep,” says University of Michigan clinical associate professor Marion Hofmann Bowman. “But as long as their hearts can speed up when necessary, this is perfectly fine.” Call this form “normal” bradycardia.
“Steve’s problem wasn’t that his heart rate at rest was slow,” Mountantonakis says. “It was that he couldn’t mount a good rate response when he needed it to beat faster.” Call this type “symptomatic” bradycardia, a condition characterized by fatigue, lightheadedness, dizziness, fainting, and quickly diminishing endurance in the pool.
The good news, as Reiss would soon discover, is that even the bad kind is eminently treatable.
Pacemakers have come a long way since the first external cardiac pacemakers were built about 90 years ago. Early versions, though effective, plugged into a wall socket and carried a potential hazard of electrocution. Fortunately, technological refinements since then have led to safe, effective, implantable pacemakers that operate on long-lasting lithium batteries and feature complex computer algorithms to pace each patient’s heart in ways that increasingly echo our natural physiology.
Nestled in the upper right chamber of the heart is a group of specialized cells called the sinus node. This acts as our heart’s natural pacemaker, barking out an ever-shifting stroke count like the coxswain on a racing shell. Electrical impulses initiated in the sinus travel to a secondary, back-up pacemaker called theatrioventricular node (“AV node”) and from here travel down various bundle branches to ensure a highly coordinated beating of heart muscles.
Problems can occur anywhere within this system. In some patients, Mountantonakis says, the sinus node stops working right, a condition known as “sick sinus syndrome,” or SSS. Such patients can no longer adapt their heart rate to match demand. In still other patients, the sinus is working fine. “But they have an electrical block,” he says, “that prevents these signals from being transferred throughout the whole heart.”
The cause for such problems is not always clear, though aging and scarring of heart tissue from diseases that inflame heart muscles often play a role. Regardless of cause, once our natural pacemaker system stops working, the remedy is replacing this with an artificial pacemaker.
In the most recently available data, pacemaker use in the United States has climbed by 56 percent over the past two decades. Sarasota YMCA Sharks Masters member David Oakes, 78, had his pacemaker implanted about 10 years ago after his Holter monitor revealed bradycardia and erratic heartbeats during exercise. Since then, he says, the skipped beats have stopped entirely. “I have been able to train and race and lead a completely normal life with my pacemaker,” he says. “I don’t even know I have one 99 percent of the time.”
In this, he’s hardly alone—several years ago, Oakes and his similarly afflicted relay buddies set what they joke may be the first all-pacemaker world record.
Other Masters swimmers credit their devices as lifesavers. Bill Radack, 80, is a former high school All-American who still competes despite having suffered several heart attacks. Radack has a hybrid device that’s part pacemaker, part automatic defibrillator. The former, for the most part, keeps his heart rhythms stable, and the latter serves as a back-up in case his heart does go haywire and he needs to be shocked back to normal.
At a recent local meet, Radack says, he received just such a shock while racing a 50 backstroke. He describes the sensation as feeling “five times worse than touching an electric fence.” Still, he’s grateful. “It’s like a life insurance policy,” he says. “I’m not afraid to go all out in a race because I know if my heart does go out of whack, this device will bring me back.”
A Better Way to Pace?
Pacemakers come in many varieties and feature different bells and whistles, depending on a patient’s condition. Mountantonakis, the cardiologist from New York, recommended to Reiss a recently approved device that seems particularly friendly to swimmers. Made by the German company BIOTRONIK, it’s compatible with full-body MRI, something that older models don’t allow. Potentially even more important is its sensor technology.
“Most pacemakers,” Hofmann Bowman, the University of Michigan professor, says, “rely on accelerometers to tell the pacemaker, ‘OK, now I’m exercising, I need more heartbeats.” Accelerometers work well for land-based exercise, where gravity and physical pounding make it easy for the gizmos to detect motion. “But my hypothesis is that because there is less pounding and gravity involved, it’s very difficult for the pacemaker to know that one is swimming and needs more beats per minute,” Hofmann Bowman says.
She suspects this failure-to-detect caused her own swimming teammate, Ted Erikson, 90, to pass out during a 50 freestyle last January. An International Marathon Swimming Hall of Fame inductee, Erikson recalls trying to catch up to and beat a friend “when oblivion descended at the 45-yard mark.” Lifeguards quickly rescued him, and he soon regained consciousness. At the hospital, doctors found nothing wrong beyond a case of “syncope,” or fainting—a not uncommon consequence of cardiac demand exceeding output.
Hofmann Bowman and Mountantonakis both believe a different sensor system pioneered by BIOTRONIK may help prevent such a mismatch in swimmers. It’s called CLS, for “closed loop stimulation,” and unlike accelerometers that key in on physical movement, this technology functions as a miniaturized EKG capable of sensing how hard the heart itself is squeezing. “Whether your heart muscle is squeezing harder because of exercise, stress, anger, or anything else that excites the heart,” Hofmann Bowman says, “this technology detects increased impedance and tells your heart to beat faster to meet increased demand.”
Though the number of swimmers with CLS technology is still too low to yet prove an advantage in Masters swimming, studies have shown a significant benefit in adjusting heart rate according to mental stress, as well as a seven-fold reduction in fainting episodes.
Reiss’s change in exercise capacity post-pacemaker has proven remarkable. Once cleared to swim again, he was amazed how quickly his old endurance capacity returned.
The only problem, he says, was a short lag—20 to 30 seconds or so—before the higher heart rate kicked in. “So, I went back to the doctor and he just adjusted it,” Reiss says. “I don’t pretend to understand how, but he put this magnetic thing over my heart and used a computer to adjust the pacemaker’s sensitivity and timing. The net effect: There’s no lag anymore.”
Reiss is hardly alone in feeling reborn athletically through modern technology. “It’s a hard decision to implant a pacemaker in someone who is active,” Mountantonakis says. “But if your heart rhythm has proven to be a problem, then the pacemaker can correct that and afterwards there are no limitations. Athletes can go back to their regular routine.”
Reiss, for his part, knows his artificial pacemaker isn’t identical to his former natural one. “But it’s pretty damn close,” he says. “I honestly can’t tell any difference from what I was before the problem first arose.”
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