Interview conducted by Alexander Chilton, BSc Hons
How long do pacemakers (and also internal cardiac defibrillators or ICDs) typically last and what causes the system’s lead wires to fail?
The pacemaker or ICD unit, which is the implanted box or generator i.e. the electrical component of the device that's implanted in the chest, usually lasts between seven to 10 years before the generator’s battery is depleted.
Cardiac leads are the conductor wires that connect the pacemaker to the heart. They are designed to function and remain in place as long as the leads themselves are undamaged or no infection is present. It's very common for those leads to last 10 to 15 years. But their lifespan is not infinite by any means.
The human body is very hostile to any foreign bodies, and leads are affected by that. As the body moves, it can cause the leads to wear physically. Also, scar tissue can form in the venous system around the leads, also causing stress. Due to differences in cardiac lead designs, materials used and the individual patient, the moment when noticeable lead wear begins and the progression of this wear to the point of lead fracture or failure can be quite variable.
What damage to the body can old leads cause if they are left in place?
If the leads are still being utilized after the pacemaker battery is depleted, the electrophysiologist, which is the specialist who addresses these situations, will go directly in and disconnect the spent pacemaker from the leads and usually replace the generator with a new one.
If the leads are still intact and they are performing as expected, they will likely be reconnected to the new pacemaker or ICD and continue to be used. Research has found that over time there will be an overall increase in the amount and location of scar tissue that can bind the leads to the vein or cardiac walls. After a number of years, calcification commonly forms within the scar tissue that surrounds a lead. This makes the binding tissue stronger and more difficult to disrupt when an extraction procedure is performed. But if the lead is working normally, there is no ill effect to a patient from scar tissue accumulation as long as no infection is present.
Please can you give our readers a brief overview of the history of lead extraction tools?
Cardiac lead implantation began in the late ‘50s, early ‘60s. But it wasn't until the late ‘70s, early ‘80s, that we understood that patients with pacemakers were surviving longer and were beginning to outlive their initial devices. This increased longevity lead to more generator replacements, as well as a greater opportunity for infection and damage to the leads. As a result, the leads themselves became a concern as patients outlived the devices’ expected working life.
Early on, pacemakers were implanted primarily to improve a patient’s quality of life for two years or less. Later, as patients lived much longer with pacing systems, it became clear that some sort of lead extraction procedure would be required.
Without specialized extraction devices, physicians initially tried to remove a lead by simply pulling it out. The medical community quickly realized that significant pulling force alone can cause stress to both the lead and to the patient. There were three possible scenarios when a lead was pulled. Pulling could 1) result in serious damage to the heart or to a vein leading to serious patient injury or death, 2) result in the breakage or fracture of the targeted lead or 3) the lead could slide out without problem. With two of three potential outcomes being undesirable, a better solution was needed.
Clinicians tried a variety of unusual techniques including tying the cardiac lead to a four to five-pound weight that was suspended over a pulley hoping that over time the lead would be drawn out gradually. Unfortunately, this creative approach proved unsatisfactory. Finally, open surgical chest procedures were used. While such invasive procedures were believed to have an increased morbidity and mortality than a less invasive or percutaneous approach, open chest procedures, also called, a thoracotomy, offered a viable alternative when extracting a lead.
It was in the mid-1980s when it became obvious that physicians needed a specialised set of percutaneous lead extraction devices. A number of medical device companies and individual inventors came up with ideas. None, however, worked with consistency.
Then in 1989, Cook Medical, created the first locking stylet. This is a specialized wire that can be inserted and secured within a cardiac lead. This innovation proved to be the most important part of the modern mechanical lead extraction procedure. That’s because one of the basic tenets to extracting a lead is to maintain consistent control of the lead at its most distal location where it interfaces with the heart.
Using the newly developed locking stylet secured within the lead, a knowledgeable physician could establish a strong transvenous rail over which specially designed extraction tubes or manual mechanical sheaths could be passed. Cook Medical extraction sheath sets, developed by pioneering physician, Dr Charles Byrd, were the second important device within a specialised extraction set.
So the combination of both the Cook Medical locking stylet, which locks at the most distal end of a lead coil, and a mechanical extraction sheath, were the primary set of devices that evolved into modern extraction technologies. Even today, while devices have greatly matured over the last 25 years, the basic premise on how best to mechanically remove leads has not wavered since day one.
Why do you think that the need for lead removal is growing year on year?
There are a couple of reasons. The most important part is that the number of devices being implanted is increasing. The second part of that is, as I mentioned earlier, the patients that are receiving devices today are much younger, much more vibrant from a health standpoint, and have an expected longevity after their first implant in many cases of 40 to 50 years.
As a result, because the number of patients living with devices is growing, the percentage of those patients that will have some event, whether it's an infection or a compromised lead, requiring extraction just continues to grow.
The third reason that number of leads being extracted is increasing is because the number of leads that are present being implanted in patients is also going up on average.
For example, a recent advancement in rhythm management therapy is called biventricular pacing. This therapy synchronously paces both the right and the left side of the heart to allow the heart to be a more efficient pump. Patients with congestive heart failure usually have a very desynchronous heart, meaning that the contraction of the left and the right side of the heart are not in unison. In these patients the heart beats in a very disorganized - almost a “washing machine” fashion.
So by having a cardiac lead not only going to the two chambers on the heart’s right side, the right ventricle and the right atrium, physicians now insert a third lead through a small vein which opens into the right atrium and actually goes around to the left side of the heart. Because of this third lead, bi-ventricular pacemakers can pace both the left ventricle as well as the right side.
As a result, you have a much more synchronous heartbeat. But you also have an extra lead which may ultimately need to be removed.
What do you think the future holds in terms of the number of cardiac leads that will require extraction? Do you think you'll ever get to the point where you don't need to extract any?
As long as the devices are going in and they are in existing patients, the reality that some sort of bulletproof lead could be invented really is, in my humble opinion, a pipe dream. Leads have always been the weakest link in pacing technology. They've come a long way in their design and fabrication. While materials have markedly improved, the stresses that the human body subjects on a cardiac lead over many years of implantation will continue to impact their functional longevity.
As hard as the global healthcare system works to eliminate infections in patients with cardiac leads, there will likely continue to be a low baseline infection rate that will be difficult to completely eradicate. Anytime a generator is replaced with a new one, the chance of infection is known to slightly increase. So while the goal remains to decrease the number of device-related infections, which I think in in most institutions is happening today, the reality is that there is still going to be a need to remove some cardiac leads because of infection.
Also, whether it is an implanted cardiac lead connected to a conventional pacemaker or ICD or a next-generation pacemaker that does not have leads at all but is implanted directly into the heart, each would occasionally need to be removed. History has shown a correlation between the length of time a lead is implanted in a patient and the level of effort required to remove it.
What are Cook Medical’s plans for the future?
Over the last year or so, Cook Medical released its Advanced Platform of devices for lead extraction. Mechanical extraction has provided consistently optimal procedural performance over the last 25 years. Plus its cost has historically been much lower than most powered alternatives. This is significant as procedural expense is quickly becoming a critical discussion topic for hospitals and health care systems worldwide.
There are various electro-thermal powered extraction devices, such as sheaths that operate using electrosurgery or laser energy that have been marketed since the late 1990s. Each device has individually contributed to the growth of the lead extraction procedure. However, I think that if you look at the cardiac lead removal world today, the general progression is moving towards powered mechanical extraction systems where Cook Medical is recognized as the pioneering leader and has been for a quarter of a century.
The Evolution RL, a device that we released most recently, has been designed to very efficiently address the challenges that come with pacemaker lead extraction. The next hurdle that we are all going to experience as an industry, from a device extraction standpoint, is the extraction of totally implanted pacemakers. Three major pacing companies are in the process of developing their own version of these devices that are inserted within a heart chamber and do not require conventional cardiac leads.
In today's world, this industry is global: it is not just the US or Europe or APAC. Physicians, whether they are in Sri Lanka, Argentina, Canada, US or the UK, now all have access to the cardiac rhythm management technologies such as general cardiac pacing, ICDs or Bi-Ventricular pacemaker therapy. As such, they also need to perform lead extraction procedures.
Extraction for a while was really just a Western hemisphere type of technology. Now there must be a global approach to device knowledge and procedural education. I think from Cook's standpoint, we are very committed to making sure that the knowledge base for extraction continues to expand globally.
One thing that Cook Medical has done very well over the last 25 years is that we have created and established a very strong working relationship with the major pacing companies from around the world. They come to Cook Medical for insight and consultation on extraction. Today, we are excited to be able to work with pacing companies on a whole platform of new devices to extract totally implantable pacemakers.
The key to the growth of this technology is not just a trial and error approach to creating a tool. It is really a long-term integral understanding of the intricacies of what we're trying to accomplish and then making it all happen.
Many medical device companies have a continuous influx and outflow of critical individuals that makes long-term continuity and device development programs somewhat difficult to keep on point. Within the strategic management, product development and regulatory affairs teams at Cook Medical’s Lead Management division, nearly all of the managers and engineers have been engaged in this niche business since its conception. So we provide a continuity no other company can match in this area.
Where can our readers find more information?
About Barry Norlander
Barry Norlander joined Cook Medical as a Clinical Product Specialist with the Vascular division in 1992. Mr Norlander has held a number of positions at Cook Medical over the past 23 years and was appointed to the role of Global Marketing Manager for Cook Medical in 2006. He has significant experience in Lead Extraction having been the Product Manager of Cook Medical Lead Extraction™ Equipment for over 20 years. He has also written a number of papers on Lead Extraction. He has a BA in Economics and Business Administration from University of Pittsburgh and holds an AS in Respiratory Therapy from Community College of Allegheny County. Prior to joining Cook Medical, Mr Norlander worked in a clinical setting for four years as a Respiratory Therapist and Technician.