Leadless Technology May Free Pacing and ICDs From Transvenous 'Tethers'

Reed Miller

June 28, 2012

June 21, 2012 (Nice, France) — The next "disruptive" technology in pacemaker and ICD technology may be devices that do not have any transvenous leads or perhaps no leads at all [1].

The potential for leadless pacing in particular could allow for, among other possibilities, pacing at more than two ventricular sites, left ventricular endocardial pacing, epicardial pacing, and transapical pacing, Dr Bruce L Wilkoff (Cleveland Clinic, OH) said during a debate on leadless cardiac rhythm management devices at Cardiostim 2012. He described self-contained, small pelletlike pacing devices that could be installed under local anesthesia in the right ventricular apex, left atrium, an epicardial location, the coronary sinus, or multiple sites. Multiple devices could be implanted to work in concert with each other "without the tethers" of current transvenous lead-bound technologies, he said.

"There seems to a need to innovate. We need to do more with this therapy, and we're limited by this venous-access issue," Wilkoff said. "Why would we want to go through this? It seems like a lot of complexity, but we already have complexity." Listing fractures, erosions, and infections with transvenous leads as examples, Wilkoff argued: "We've been living with all of this lead complexity for a long time."

Innovative power technologies will be key to the leadless devices. For example, Wilkoff mentioned an Israeli company called Sirius that developed a piezoelectric power generator that would use the motion of the heart to create enough electricity to power the device as a "self-perpetuating" battery. Also, several companies are working on systems for delivering power from outside the body without wires.

Technology for implantable defibrillators without transvenous leads, albeit not completely leadless, is already a clinical reality and was the topic of a session at Cardiostim that drew a standing-room-only audience. As reported by heartwire , data from the EFFORTLESS registry presented at the meeting show that the subcutaneous implantable cardioverter defibrillator (S-ICD) (Cameron Health/Boston Scientific) is saving the lives of patients at risk for sudden cardiac death with a gradually shrinking rate of inappropriate shocks. Especially in young patients at risk for sudden cardiac death, "there are strong reasons to avoid all of the problems to do with the endocardial lead," Dr John Morgan (Southampton University, UK) said.

The Future Hasn't Arrived Yet

However, a major limitation of this technology, mentioned by Morgan and several other presenters at the conference, is that many patients who need ICDs also need antitachycardia pacing, which the subcutaneous device cannot possibly deliver, limiting the patient population that can benefit from the S-ICD. But in the future, patients in need of both sudden cardiac death prevention and antitachycardia pacing may get two separate leadless devices either simultaneously or at different times as their disease burden evolves, Morgan said.

Despite the potential upside of leadless devices, the technologies have a long way to go before they will replace devices with transvenous leads, Dr Johannes Brachmann (University of Würzburg, Germany) cautioned. "For the vast majority of patients, the transvenous lead is still [a technology] we can apply with a great deal of certainty," he said. "The vast majority of patients do very well with transvenous leads today.

"We simply do not have very good long-term data" on the leadless or subcutaneous devices, as there have been no randomized trials directly comparing the performance of a subcutaneous or leadless system and a system with a transvenous system. "They're just assuming this system can provide the same information and the same effectiveness as the existing devices, but this has never been proven," he suggested. The 330-patient, 33-center trial that earned the S-ICD a favorable review from an FDA advisory panel compared the device with objective performance criteria. "We need sound evidence to use this technology. This will not be technology that can be easily implemented. It will require major investments on the part of industry," he said.

Wilkoff granted that [completely] leadless defibrillators and pacemakers are still a ways off, "but we are at the place of disruptive innovation, and we need to move on to the next step, and this is where we're going."

Wilkoff is an unpaid advisor for Medtronic, St Jude Medical, Spectranetics, and Cameron.