In 2015, it is hard to imagine the small working-class city of Wilkes-Barre, PA as a seat of pacing innovation. Keep reading; it's a cool story.

What excites me most about His-bundle pacing (HBP) is that so few see it. At the Heart Rhythm Society (HRS) 2015 Scientific Sessions, thousands gathered in a grand ballroom to hear about a complex futuristic device done in 39 patients in Eastern Europe, while downstairs in the poster hall, two private-practice doctors quietly presented compelling data using basic FDA-approved leads and devices.

Over the past decade, the electrophysiology community has struggled to understand the underpinnings of pacing-induced dyssynchrony and cardiac resynchronization therapy (CRT). We know right-ventricular (RV) pacing can be bad. We know CRT works, at least some of the time. But what is CRT? Is it not merely a complicated solution for a failed conduction system—a juryrigged way to simulate the synchrony of His-Purkinje conduction?

Dr Pugazhendhi Vijayaraman

In 1978, long before pacing-induced cardiomyopathy or CRT were ever conceived, Dr Benjamin Scherlag and his colleagues in Oklahoma City demonstrated that the His bundle had predestined tracts. Bundle branch block was due to focal disease within the body of the His bundle[1], and HBP (seemingly north of the block) could normalize bundle branch block[2].

Drs Pugazhendhi Vijayaraman and Gopi Dandamudi (Geisinger Health System, Wilkes-Barre, PA) paid heed to these observations and have shown that HBP is feasible, safe, and efficacious in multiple abstracts presented here at the HRS meeting. More provocatively, HBP, in their hands, can reverse both right and left bundle branch block in a vast majority of patients. Pause on that for a moment: reverse left bundle branch block!

Here is a summary of their data:

  • They started HBP in 2010, and in this abstract[3], they attempted implantation in 242 patients. Success improved from 75% in 2010 to 91% in 2013. Vijayaraman told me the advent of a newly designed sheath helped a lot. Procedure time was under 80 minutes, X-ray time was approximately 10 minutes, and chronic threshold was 1.4 V.

  • Eight patients with HBP presented for generator change and had stable lead function[4]. That's over an average of 70 months of lead stability. Vijayaraman told me longevity is improved because they no longer use backup RV pacing leads. This allows them to use a regular dual-chamber generator rather than a CRT generator.

  • HBP reversed both and right and left bundle branch block in 48 of 53 patients (83%). QRS duration decreased from 142 ms to 125 ms on average[5].

  • Contrary to historic teachings, His-Purkinje block could be normalized in 76% of patients who presented with advanced AV block[6]. These data provocatively suggest infranodal block is more often within the bundle (intra-Hisian) than below the bundle (infra-Hisian).

Dr Gopi Dandamudi

The group recently published a series in the journal Pacing and Clinical Electrophysiology in which they recorded acute injury from His-bundle sites. Injury current predicted low thresholds and long-term lead stability[7]. This February, they teamed up with a group at Virginia Commonwealth University and published a comparative study in the Heart Rhythm Journal in which HBP outperformed standard RV pacing[8].

Drs Vijayaraman and Dandamudi are not the only doctors working on this technique. Dr Daniel Lustgarten (University of Vermont, VT) and colleagues are doing impressive work with HBP  in patients with CRT indications. He and his colleagues performed a crossover study in a small number of CRT-eligible patients in which HBP looked equivalent to CRT in QRS narrowing and quality-of-life and ejection-fraction gains[9]. (There is also a group from Roverto, Italy doing active HBP[10].)

Comments

If these remarkable findings can be replicated by others, and I think they can, HBP could be the next disruptive "advance" in cardiac pacing. I put advance in quotes because the concept is really not new; it's being restored from a 25-year dormancy.

On a basic physiology level, these findings change standard thinking about His-Purkinje function.

From a bradycardia-therapy standpoint, HBP prevents the deleterious effects of RV apical pacing.

From a CRT view, HBP accomplishes with two leads what we now do with three leads. Less is more . . . again.

Select secure lead [Source: Medtronic]

Taken together, there is too much potential gain to ignore. These observations deserve our attention. And if electrophysiologists try HBP and are successful, industry will follow with improved designs.

At his poster, surrounded by only a handful of attendees, I asked the soft-spoken Dr Vijayaraman what factor holds this technology back. He did not hedge. He said it was inertia. "Doctors think it's too hard." He assured me it was not.

It is time for the EP community to give HBP a fair shot.

JMM

Comments

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