Many important innovations have been made over the last 50 years to improve the efficacy of transvenous pacemakers implanted in cardiac patients worldwide. Despite modern advancements, there remain certain risks associated with the implantation of such devices, and long-term complications are not uncommon. Though still relatively new in Canada, leadless pacing system technology is emerging as an alternative to conventional pacemakers. Without leads tethered to the heart to deliver an electrical impulse, leadless systems represent a new option for patients with bradycardia (abnormally slow heart action). But are wireless pacing systems really the way of the future?
The short answer is yes says Dr. Calum Redpath, a Clinician-Scientist and Staff Cardiologist at the University of Ottawa Heart Institute, who in March of 2018 completed the first successful implant procedure using a leadless device in one of his patients. The procedure was the first and only completed at the Heart Institute to date. Dr. Redpath implanted a Micra™ Leadless Transcatheter Pacing System, the newest and smallest leadless pacemaker in the world, intended for patients who require a single-chamber pacing solution. Unlike most pacemakers which are placed in the patient's chest with leads connecting the pacemaker to the heart, the Micra™ is implanted directly inside it. The system was approved by the Food and Drug Administration for use in the United States in 2016, and was later approved for Canadian use by Health Canada.
“Rather than having a lead which connects the pulse generator to the heart, this leadless transcatheter pacing system uses grapnel hooks which connect directly to the heart tissue, taking up less space inside the patient’s body and reducing the risk of infection and other serious complications.”
- Dr. Calum Redpath, University of Ottawa Heart Institute
The Micra™ system is considerably smaller – almost twenty times smaller than a traditional pacemaker – and with a battery longevity estimated at 12-13 years, it lasts nearly twice as long. No bigger than a large vitamin capsule, it can be implanted directly into the heart via a catheter through the femoral vein, a procedure which is favourable to patients at risk of infection because it spares the need for a chest incision. Though the cosmetic advantages are appealing, Dr. Redpath is hesitant to recommend a leadless approach to everyone. There is still too much to learn, he says.
Traditional transvenous pacemakers (those with leads) are known to carry exceptionally low failure rates, one of the reasons Dr. Redpath believes these systems are still preferred in clinical practice. However, occasionally the leads themselves cause problems. “A major benefit of a leadless system is the avoidance of lead-related complications,” said Dr. Redpath, adding that infections of the heart tissue resulting from transvenous pacemakers can require high-risk procedures to remove and replace leads and eradicate life-threatening bugs. Patients who are at risk of infection or who have previously experienced one are the most likely candidates to receive a leadless device, as are patients who have experienced a chest operation, and women with breast cancer.
There are medical reasons not to implant leadless devices, too, explained Redpath.
“We have decades of experience in implanting conventional transvenous systems. Finding novel problems in technology which has been used in millions of patients over several decades is pretty unusual. This leadless technology has only been around for 3 years. We have yet to learn what unexpected problems there may be as a result of implanting these devices.”
Dr. Redpath is optimistic but remains cautious about the future of leadless pacing. In technological terms, leadless devices represent a major leap forward, he said, but further technological advances, such as development of dual or multichamber leadless devices, are still needed to determine whether conventional transvenous pacemakers are to be replaced by leadless technology in the future.