The New User-Friendly Pacemaker
Roland Sarrazen thought he was going crazy.
He had been a martial arts instructor for nearly 18 years, had taught judo, aikido and karate, had been physically sharp and well conditioned.
Then, over a period of time, and without any discomfort or pain, Sarrazen began to find that he was unable to perform relatively simple physical tasks. He couldn’t teach martial arts. He couldn’t exercise. He became easily fatigued and lethargic.
After nearly six years of not knowing what was wrong, he had a severe attack of cardiac arrhythmia--irregular heartbeat--and was told that his condition was terminal. During the attack, he said, his heart was beating at rates too fast for the muscle to pump blood. With the next serious attack, he was told, he would likely die.
Sarrazen believes he was saved in 1979 by the implantation in his chest of an artificial heart pacemaker, which maintained his heartbeat at a uniform 70 beats per minute. But within the next five years he began to suffer from a phenomenon known as “pacemaker syndrome,” in which the patient, in spite of the uniform heartbeat, becomes progressively fatigued. Sarrazen began to feel himself slipping once again.
Today, however, the 48-year-old Sarrazen swims, hikes, even jogs a bit--activities made possible by an experimental pacemaker he received in 1984 that automatically adjusts the wearer’s heart rate in response to physical activity.
Nearly all other pacemakers available today in the United States are designed to be fixed at a uniform number of beats per minute, usually 70. They maintain that rate whether the wearer is running a marathon or sitting in a chair.
The new device, called Activitrax, is the first single-lead-wire, rate-responsive pacemaker to become commercially available in the United States, according to its developers, the Minneapolis-based company Medtronic Inc. It received official marketing approval from the federal Food and Drug Administration on Thursday.
Electrical Impulses
Usually implanted in the upper chest between layers of fat and muscle tissue, the rate-responsive pacemaker is attached to a wire threaded through veins into one of the upper chambers of the heart and delivers electrical impulses that stimulate contractions of the heart muscle at rates between 60 and 150 beats per minute.
It will sell for about $4,800, a few hundred dollars more than a fixed-rate pacemaker.
According to cardiologists who helped test it, the Activitrax is a breakthrough for pacemaker wearers who have diseased upper heart chambers because the only other rate-responsive pacemaker available in the United States relies for its function upon healthy upper chambers. (That pacemaker uses dual leads, one of which senses the healthy heart rhythm from the upper chambers and transmits corresponding impulses through the second lead to the malfunctioning lower chambers.)
The new pacemaker weighs about 1 1/2 ounces and is a little larger than a silver dollar. Inside is a tiny forest of microcircuits and a minute, flexible crystal that emits electrical impulses in response to pressure from body motion.
All but Back to Normal
“With my first pacemaker I could get around, I could do minimal things--about 30% or 40% of normal activity for a person my age,” said Sarrazen, who lives in Buena Park. “Since getting the new one, though, I’m able to do maybe 80 to 90% of the activity I was able to do in the past.
“The doctor is telling me that I’ll have a totally normal life span.”
Sarrazen’s doctor is John Messenger, chief of the coronary care unit at Memorial Hospital in Long Beach and an associate professor of medicine at UC Irvine Medical Center in Orange. Messenger, a cardiologist, was a chief clinical investigator during the development of Activitrax and implanted the device in 15 Southern California patients--one of whom was Sarrazen--during the 3 1/2-year experimental period.
“Our philosophy is that a patient should be as close to normal as possible,” Messenger said. “With the fixed-rate pacemakers, we were saving people from dying but they weren’t functionally active. With Roland, we wanted to turn him back into a semi-jock.”
The idea of a rate-responsive pacemaker is not new, and there have been a handful of attempts at perfecting one using various methods in the last five years, Messenger said. But success has been limited, said Ken Anderson, a research engineer at Medtronic and the inventor of Activitrax.
‘Just Sat Around’
Artificial heart pacemakers have been in use for only 25 years, said Anderson, and “ever since it all started we’ve wanted to do something more than just provide the minimum rate. We’ve been after this one for quite a while. We were looking at a lot of patients with not enough blood flow to the body to support any lengthy activity. They just sat around.” He said special filters built into the device help distinguish between actual bodily activity and the motion produced from, say, riding in a car over a bumpy road. While such external motion will produce slight changes in the heart rate--perhaps 10 to 15 beats a minute--most people are unlikely to notice any change.
During clinical trials, more than 300 Activitrax pacemakers were implanted in patients in the United States and more than 4,000 worldwide, Messenger said. Results of the studies showed that patients generally could stay on a treadmill longer, perform greater quantities of work and sustain greater heart rates with the new pacemaker than with fixed-rate pacemakers. Age made no difference in bodily response to the device, he added.
One of the younger patients to receive an Activitrax in 1984 during the experimental period was Barry Brush of Huntington Beach. Brush, now 33 and a student at Golden West College, suffered from congenital heart block, which caused his heart to beat “at a standing rate of about 40 beats per minute and not much more than that even with exercise,” he said. “Dr. Messenger said that at my age it was better to get a pacemaker now than later in life, when it could be a more dangerous situation.”
Brush’s first pacemaker was fixed-rate and “I would get winded real easily,” he said. “For instance, when I stood up real quickly I’d feel short of breath.
“Now, with the new pacemaker there’s a tremendous improvement. I can’t play full-court basketball, but I can swim and walk and ride a bicycle.”
Simple Procedure
The operation to implant a new device is a simple one, Brush said, performed with a local anesthetic. An external pacemaker is attached to the heart lead to keep it pumping regularly while the new pacemaker is being implanted in a small pocket in the skin of the chest.
Like all pacemaker wearers, Brush’s condition is checked regularly, about every two months. And, like many such patients, he doesn’t have to go into the hospital for a checkup. Instead, he “sends” an electrocardiogram to a hospital monitor via impulses transmitted sonically over the telephone.
If for any reason the pacemaker’s rate needs adjusting, it can be done instantly and non-surgically from outside the body by pressing a programmed magnetic device to the patient’s chest over the implantation site, Messenger said.
Where pacemakers of two decades ago could be as big as a hockey puck, required major surgery for implantation and sometimes ran on a single battery for no longer than a year, the new-generation devices are expected to run between six and seven years if the patient is active, eight to 10 years if he’s sedentary, Messenger said.
Also, they can be adapted to leads that may already have been implanted.
Pacemaker development and experimentation in the U.S. lags behind Europe because of more stringent regulation by the FDA, said Messenger, but knowledge is communicated within what he called a small fraternity of avid researchers, engineers and physicians.
“In the modern era of pacing,” he said, “it’s really kind of a closed club. There are about 100 doctors worldwide who really like working with this stuff. We love it. It’s almost like a hobby.”
For the pacemaker fraternity, he said, the Activitrax is the new wave, but by no means the final one. Messenger said he and other physicians and designers are working on the development of a dual-lead version of Activitrax, and also a more sensitive device that would be responsive to changes in the individual’s blood temperature.
