CardioStim 2014, Day 2: Nano, Mobile, and Wireless . . . Is Electrophysiology on the Cusp of Disruption?

John Mandrola


June 19, 2014

Anytime a new technology comes with the suffix "less," I get interested. Less, as in leadless implanted devices, may indeed be the future of cardiac pacing. Multiple studies presented here at CardioStim 2014 lend credence to such a bold statement.

The stuffy and small conference room was as packed as I have ever seen one. Attendees lined the walls, aisles, and even sat on the floor. As I sat there in a rickety chair, I worried about a vasovagal episode, falling onto my lap and laptop.

The session was given the provocative title, "Revolutionary Technologies for Implantable Devices." The first presentation included the terms, "First-in-man . . . "

The tech-hungry crowd, therefore, was not surprising.

The driving force for devising a way to stimulate the heart without permanent transvenous leads is the impossibility of engineering the perfect lead. I had a student with me recently during an implant, and she asked a question that many of us experienced electrophysiologists easily forget: "Does that lead do damage going through the veins and heart valves?" It was striking that even a novice could recognize the weak link of current pacing systems.

So it is that companies big and small are entering the race to develop a wireless pacing system.

heartwire journalist Michael O'Riordan has this coverage of the very early (as in four patients early) experience with the Medtronic Micra self-contained leadless RV pacing device[1]. Dr Clemens Steinwender (Linz General Hospital, Austria) presented their experience with the 2-g self-contained device, which is delivered through a deflectable sheath placed via a femoral approach. Much like the St Jude Medical NanoStim leadless pacemaker, except with tines instead of a screw, the Micra device provides excellent acute pacing performance. The one-month follow-up pacing parameters remained unchanged, and no complications were observed.

In the following presentation, Dr Fleur Tjong (Academic Medical Center, Amsterdam, the Netherlands) presented one-year follow-up of their eight patients from the original 33 patients enrolled in the LEADLESS trial, which enrolled 33 patients implanted with the NanoStim leadless pacemaker[2]. This trial was last updated at Heart Rhythm Society Sessions last month. The Dutch team reported today that their eight patients had excellent pacing parameters, rate-responsive functionality, and no adverse effects.

The St Jude NanoStim device has a clear head start in the leadless pacing race, with two trials, one in North America and another in Europe, currently enrolling patients.

Leadless in the LV?

Leadless pacing isn't just going on in the right ventricle. Remarkably, the technology is also being considered and studied in the left ventricle (LV). That's right, a metal lead on the arterial side of the circulation.

The idea is to offer cardiac resynchronization to the 10% to 20% of CRT-eligible patients who are not suitable for transvenous coronary sinus leads. These patients have a problem because the only option at this point is to surgically place an epicardial lead, which, despite some surgeons' opinion, is far from "less" invasive.

In a session yesterday at CardioStim, Dr Peter Neuzil (Na Homolce Hospital, Prague, Czech Republic) presented a series of 14 patients implanted with a cardiac resynchronization therapy (CRT) device equipped with a wireless LV endocardial pacing system[3]. The Wireless Cardiac Stimulation System (WiCS-LV, EBR Systems) comprises an ultrasonic transmitter and leadless pacing electrode, the latter implanted directly on the LV endocardium. My understanding of this system is that a small leadless pacemaker is implanted in the lateral LV endocardium via a retrograde aortic sheath and intracardiac echo guidance. Once affixed inside the LV, an ultrasound transmitter is implanted in a nearby intercostal space. The extracardiac device senses RV pacing stimuli and 10 ms later delivers an ultrasound pulse that tells the LV device to pace. (Wow.)

The researchers achieved cardiac resynchronization in 12 of 14 patients. There were three patients who developed procedure-related adverse events, including pocket hematoma, femoral pseudoaneurysm, and cerebrovascular accident in an AF patient in whom warfarin was interrupted. The authors concluded that wireless endocardial LV pacing provided consistent stimulation with QRS narrowing in patients with prior failed CRT systems.

This is not the first group to report results with this novel pacing system. A different group of European researchers reported a series of 17 patients in EuroPace earlier this year[4]. They found similar efficacy results, but enthusiasm was dampened by the report of three patients who had pericardial effusion, including one who died as a result. In the discussion section, the authors noted that the effusions were likely related to the sheath, not the lead, and that design improvements were planned.

Seeing the Future

I have the sense that we are on the cusp of something big. Looking back on the past 20 years of implanting devices, the repeating problem is the lead. Everyone knows it. And it is ironic that our biggest lead mistakes have led to some of the most significant advances. The Sprint Fidelis lead (Medtronic), for example, accelerated the development of noise-detection algorithms, while the Riata (St Jude Medical) changed our collective view of lead size and the need for a superior vena cava (SVC) coil. (That's the thing about mistakes: no one likes to make them, but they sure do teach a lot.)

So now, nano and wireless technology may be leading a major disruption in delivering electrical stimuli to the heart. Yet I know you want more than just the wishful meanderings of a jet-lagged columnist.

This is why I emailed one of the most knowledgeable guys in my inbox. It was a pleasure to sit down with Dr Charles Love (New York University, New York) this afternoon at CardioStim. I wanted to get the impression of a leader in the field of rational thinking about cardiac devices, and a real doctor who has actually implanted a wireless pacemaker.

Dr Love, I am happy to report, agrees with me about the disruptive potential of these technologies. Yes, he thinks leadless pacing is the future. "Right now, the patient population amenable to wireless ventricular-only pacing is small, but think about what could happen if this technology is combined with the subcutaneous ICD?" Recall that the main barrier to subcutaneous ICDs is the lack of pacing, for both bradycardia and painless termination of tachycardia. "When we get a leadless pacemaker that communicates with a subcutaneous ICD, the benefit/risk ratio of the ICD turns strongly in favor of benefit" is a paraphrase of his comments. It makes perfect sense.


Small. (Perhaps even nano.)

And wireless.

These are the words of technology in the nonmedical world. It's got to be the same in electrophysiology. Imagine what future electrophysiologists will think of us dinosaurs who implanted physical leads that scar into blood vessels and cardiac valves.

But wait, don't think too far into the future, because then you might see a generation of caregivers who are able to cure cardiac arrhythmia with injections of cells that transform, regrow, and heal the cardiac myocyte and conduction system. Wait, that's way into the future.



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