The Evolution of the Pacemaker: A Conversation with Cardiologist Dr. Abraham Bornstein, M.D., Part II
PhysEmp CEO and Founder Robert Truog continues his discussion with cardiologist Abraham Bornstein about his life and work.
PART II
(Jump to Part I of this conversation)
Dr. Bornstein: What’s being developed right now is the lead-less pacemaker. They’re about the size of a nickel. They have no leads. The device sits right in the heart itself. Right now, they’re only geared for a single lead. Pacemakers have evolved to the point where you can percutaneously insert two or three leads in order to mimic the normal physiology of the heart. But originally, the first pacemakers accommodated only a single lead, which would pace but not be able to sense the heart’s intrinsic beats, thereby ignoring the heart’s natural rhythm. The pacemaker paced the ventricle, but there was essentially no sensing capability. Eventually, the technology advanced to where you could have not only pacing, but sensing as well. The pacemakers were capable of sensing the patient’s intrinsic rhythm, and therefore would fire only when necessary and appropriate.
PHYSEMP: And report on what the heart is doing?
Dr. Bornstein: Yes. It does automatic monitoring. You don’t even need a wand anymore, like in the old days. Back then you’d have to put a wand over the pacemaker to interrogate it for information. Today, we do it by computer over an internet connection.
PHYSEMP: What other advances have occurred in pacemakers?
Dr. Bornstein: The first, as I said, was finding the right power pack and battery. The second was in the leads. The new leads have been amazingly durable. The early leads easily fractured; the insulation would break. It would over-sense, or not fire because it sensed some other electrical signal in the vicinity. So, it would just start or stop firing because it thought the heart was doing what it wasn’t supposed to do. But that was just electrical interference. It was fixed. Now, you had a pacemaker that could not only pace, but also sense. That enhanced pacemaker longevity, as well.
PHYSEMP: I assume, from all these advances, that physicians were enabling more and more people to be likely candidates for the use of this technology.
Dr. Bornstein: Yes. But not only that; initially, in its development (circa 1960s), cardiac surgeons were putting pacemakers in by thoracotomy [a surgical procedure in which a cut is made between the ribs to see and reach the organs in the chest or thorax]. So, we started to put them in percutaneously, using a needle into the vein, then threading the wires in.
PHYSEMP: Much less invasive.
Dr. Bornstein: It’s simply a needle that negotiates the vein. You find the vein, then you thread a guidewire in. And then, over the guidewire you put in the sheath. Through the sheath, you slide the pacing leads in.
PHYSEMP: And the power pack?
Dr. Bornstein: Once the leads are in, we attach the power pack percutaneously. It has a special mechanism where you can actively fixate the lead right in to the myocardium. In 1972, we began working with the Cordis Corporation when they introduced the Omnicor line of pacemakers, the first adjustable pacers under noninvasive electronic control. This unit was based on more advanced microelectronics than earlier pacers; it included an integrated sensing amplifier and two integrated digital logic circuits in its design.
Dr. Bornstein: Dual-chambered pacing came along in the late 1970s and early ‘80s. Now you had a pacemaker that would not only pace and sense the ventricles, but also pace and sense the atrium in a synchronous fashion. These were much more physiologic.
PHYSEMP: What was the next advance in pacemakers?
Dr. Bornstein: Dual-chambered or A-V sequential pacing, where you position the leads in both the atrium and the ventricle. The other advance was that now we had a fixation device. I had patients who (this was rare but it did happen) were twiddlers. They got anxious and started twiddling and messing around with their pacemaker. It would dislodge from where it was supposed to be fixed. But with the fixation device, there was less chance of that.
PHYSEMP: And the next advance?
Dr. Bornstein: Programmable pacemakers. Pacemaker manufacturers introduced more complex and completely integrated circuitry during the 1970s, which allowed for the design of far more complex pacemakers with a number of parameters that the physician could noninvasively adjust by using a noninvasive programmer that transmitted coded instructions on a carrier signal through the patient’s chest to the implanted pacemaker. Essentially, this allowed physicians to individualize the behavior of the pacemaker for each patient. So, innumerable variations in pacing and sensing could be achieved by noninvasive programming. That led to the ability of rate-responsiveness, where the pacemaker adjusts pacing rate changes in accordance with the patient’s physical activity. One patient I had was this great tennis player who could no longer keep up with the other players. It turned out, his heart rate was way down in the 30s. That’s enough to maintain consciousness, but not really to play anymore.
PHYSEMP: What did you do there?
Dr. Bornstein: We inserted a rate-responsive dual chambered pacemaker, which senses the atrium and then paces the ventricle optimally after each sensed atrial beat. This is referred to as dual chamber, or DDD, pacing. When a patient’s heart rate picked up, the pacemaker would track that. It would sense natural cardiac electrical activity or sense a patient’s respiratory rate or level of physical exertion and respond in kind.
PHYSEMP: I’m diagnosing myself as you’re talking. My tennis game has been slowing down of late…
Dr. Bornstein [laughs]: You can program virtually everything in a pacemaker now. You can program the electrical output and the pacing and sensing thresholds, as well as programming optimal physiologic cardiac output by adjusting the timing cycle as well as the atrioventricular sequence.
PHYSEMP: Let’s keep going with other advances in the field. What else?
Dr. Bornstein: The next advance in pacemakers was insertion of hybrid devices, referred to as the internal cardioverter defibrillator, or ICD, all in a single device. So, if a patient developed a lethal rhythm, it would be detected, and then a lifesaving shock would be delivered that would correct the patient’s rhythm. I took my first patient down to Johns Hopkins by plane in 1983 when we did the first of those. Finally, those technologies were combined into one, so now you’ve got a device that’s universal, that does it all; that is, it paces and senses physiologically, paces multiple chambers synchronously, and can cardiovert and/or defibrillate any life-threatening cardiac dysrhythmias.
PHYSEMP: And three-lead pacemakers?
Dr. Bornstein: That was the next advance. Three-lead pacemakers for cardiac resynchronization therapy, or CRT, was intended for people with heart failure who had areas of abnormal contractility producing dyssynergy or poorly organized and inefficient myocardial contraction. In other words, the patient’s heart was not organized appropriately in terms of its synergistic ability to contract. One area would contract and the other would expand—resulting in the overall cardiac output ineffectively or insufficiently increasing.
PHYSEMP: So these pacemakers would, I assume, increase capacity?
Dr. Bornstein: Yes. In patients with heart failure, their longevity improved and the number of hospitalizations was reduced.
PHYSEMP: Survival rates must’ve gone through the roof for people.
Dr. Bornstein: There’s a whole subsection of the population that now experience quality life lasting anywhere from 10 to 20 years longer.
PHYSEMP: Which of course leads to the need for more healthcare. You were describing how the survival rate from these events is driving the demand for heart transplants?
Dr. Bornstein: What’s driving that demand is the number of years these people are living, and also the support they can get now, in particular what’s called “bridge to transplant,” where they have mechanical hearts while they’re waiting for a cadaveric heart to become available.
PHYSEMP: So, in effect, the technology is merging with the body. I’m wondering, where do you think pacemakers will be in five or 10 years?
Dr. Bornstein: We’ll have leadless and even battery-less pacemakers, which is a new, emerging area. As we previously discussed, it will involve new ways of harnessing the electrical-mechanical power created by myocardial contractility.
PHYSEMP: I was thinking about the nature of healthcare as opposed to other fields, where we’re seeing so much innovation and disruption. Things really have changed, haven’t they?
Dr. Bornstein: My father was 55-years-old back in 1965. He had a heart attack. They put him to bed and subsequently he died shortly thereafter. There was not much they could do for him. It wasn’t until 1972 that we had the first successful bypass surgery. Now, things move fast. People are living longer. Pacemakers have evolved tremendously, extending life, allowing people many more years to participate. It’s been incredibly gratifying to have been a part of all that.
END OF PART II
Read Part I of this conversation
