John Mandrola


September 01, 2015

After years of practice and thousands of procedures, I still love implanting a pacemaker. Patients with bradycardia often ask about options. Is there a medicine or procedure to speed up the heart?

I'm all about options, but in this case, I give the obvious answer—there is either the device or the disease.

The pacemaker is pure: the patient is sick, and I have a remedy. For sure, when the heart stops, we treat disease—not a risk factor.

But pacemakers are far from perfect. They come with risks and trade-offs. Complications such as infection and hematoma can occur at the site of the pocket in the chest. The weakest link of the pacemaker is the lead. Pacing leads are susceptible to fracture, insulation breaks, and dislodgement; they can perforate the heart, cause occlusion of the veins, and induce tricuspid regurgitation.

Like an internet connection, a pacemaker would be much better without a wire.

A study released as a hot-line trial at the European Society of Cardiology (ESC) 2015 Congress (and published in the New England Journal of Medicine) ushers in a new era in cardiac pacing[1]. Primary investigator Dr Vivek Reddy (Mount Sinai Hospital, New York) presented the results of the prospective multicenter LEADLESS II study.

In LEADLESS II, 526 patients with symptomatic bradycardia who were eligible for single-lead ventricular pacing underwent an attempt at implantation of a St Jude Medical leadless pacemaker. The 4-cm long, 6-mm wide NanoStim is a self-contained leadless pacemaker that is implanted in the right ventricle via an 18-Fr femoral venous sheath.

The results of LEADLESS II were decidedly positive. The device was successfully implanted in more than 90% of cases—despite the fact that 99 of 100 operators had never done a single leadless implant. Pacing performance was excellent at 6-month follow-up. Battery longevity is projected to be well more than 10 years, including rate-adaptive (VVIR) pacing.

Safety end points were also quite good. The incidence of cardiac perforation was 1.3%, but not all effusions required intervention. Femoral complications occurred in less than 1% of patients, and device dislodgment requiring retrieval occurred in 1.1% of patients. No patient died as a result of the device, but two deaths were related to the procedure. One patient who died had a significant bleed at the access site in the groin, and the other had a pericardial effusion that was drained but subsequently developed atrial fibrillation and massive stroke. Overall, the risk of any adverse event was 6.5%


Let's begin with the limitations of the study. As Dr Reddy emphasized in his presentation, LEADLESS II was not a randomized clinical trial. It was an observational single-arm assessment of a novel pacemaker. Follow-up was short, at only 6 months. And leadless pacemakers pace only the RV; single-chamber devices are used in a small minority of patients referred for pacing (approximately 5% to 20%).

On the matter of complications, vascular-access issues are not uncommon during any cardiac catheterization procedure. Pericardial effusion and subsequent atrial fibrillation and stroke are also complications of putting catheters in the heart, especially in the elderly. I have little doubt that rates of complications will decrease with experience.

I reached out to a couple of my go-to pacing gurus. Dr Edward "Jay" Schloss (Christ Hospital, Cincinnati, OH) said this was "exciting but challenges remain. Making a VVI pacemaker functional is step one. Getting beyond that is going to require some creativity. Think about challenges in pacing and sensing the other chambers. Think of how infrequently a VVI pacer serves the needs of your patients today."

Dr Charles Love (NYU Langone Medical Center, New York) brought up an interesting aspect of this technology, one I had not considered. In an email, he wrote, "[Leadless pacing] does open the door for [nonelectrophysiologists], and this is not as important in the US, but it has significant implications for third-world countries, where EPs are scarce."

To those who worry about overtreatment once this technology is available to any cardiologist who can get vascular access, I'd be reassured that—at least in the US—we have strict national coverage decisions for pacing and ICD implantation. (I'll resist the urge to type anything further about why we have such restrictions.)

I can't help thinking about the older patient with atrial fibrillation and AV block. This device, which can be placed in a cath lab in 30 minutes and last more than a decade, seems attractive.

More attractive, however, is the future. This week, the Journal of the American College of Cardiology features a review article on leadless pacing[2]. The authors made clear that future iterations of a leadless pacing device will likely be combined with a defibrillator generator or placed in the LV to perform CRT. During a video interview (coming soon), Dr Reddy told me companies are working on the combination of a leadless pacemaker and a subcutaneous ICD. That would be a significant advance.

It's about time electrophysiology began cutting the cord. Of course we should be careful about anything that is new and novel. Electrophysiology is best when it goes slowly. Postmarket surveillance of these devices will be critical. But all that said, I'm going on the record: This is the beginning of a great new era in cardiac devices.



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