Henry Huang, MD, FACC, cardiologist at Rush University Medical Center, recently conducted an interview with Parikshit S. Sharma, MD, MPH, FACC, electrophysiologist at Rush University Medical Center and expert in the field of Permanent His Bundle Pacing (PHBP). Sharma shares his experience and knowledge in electrophysiology as he has performed more than 100 PHBP implants and published extensively on the topic.

Huang: While it seems like there is tremendous amount of excitement regarding the potential application of PHBP, the procedure is still mostly limited to select academic centers. Can you tell us about the procedure and the appropriate patient population?

Sharma: PHBP is a more physiological form of pacing that involves permanently placing a lead at the Bundle of His (HB), typically distal to the site of potential disease or delay in the conduction system. This allows ventricular activation in a more synchronous fashion using the native conduction system, thereby minimizing the potential adverse effects of conventional right ventricular (RV) apical pacing which include incident atrial fibrillation, pacing-induced cardiomyopathy, hospitalizations from heart failure and associated mortality. The lead is positioned at the HB using a pre-shaped delivery system after mapping the AV junction/HB from the tip of the lead in a unipolar fashion. Intuitively, patients that would be ideal candidates for PHBP would be patients that have the potential need for or a high anticipated burden of ventricular pacing such as patients with advanced AV nodal disease.

Huang: His bundle pacing has been around since 2000, so why is there so much clinical interest now?

Sharma: Pramod M. Deshmukh, MD, et al., first published their experience with PHBP in 2000 in 12 patients (of 18 attempted) with permanent atrial fibrillation, cardiomyopathy and anticipated AV junction ablation. Subsequently, PHBP was attempted by various European centers. However, the lack of a good delivery system with low success rates (65 – 70 percent), need for an additional HB mapping catheter and lack of data on safety and clinical outcomes were some of the factors that limited early adoption. With the newer delivery systems, ability to map the HB from the tip of the lead resulting in improved success rates (80 – 90 percent), and emerging safety and outcomes data, PHBP has now made a comeback! It allows us to obtain a better understanding of the physiology of the conduction system and has made the world of cardiac pacing exciting for all of us again, hence the renewed interest.

Huang: What is the learning curve for the procedure?

Sharma: It is prudent that the implanting physician have a thorough understanding of the electrophysiology of PHBP and the anatomy of this region. Typically, we recommend about 10 straightforward cases to feel comfortable performing PHBP. That number might be higher before an operator should attempt PHBP for patients with an indication for cardiac resynchronization therapy (CRT) given the need for more extensive and delicate mapping in patients with remodeled atria. Thus, the learning curve might be both operator and indication dependent. To quote a recent recommendations manuscript we published in Heart Rhythm Journal, "It is reasonable to expect that any well-trained implanting electrophysiologist could learn to perform HBP with focused didactic training and case observation and/or the presence of an experienced proctor, with an approximate learning curve of 10 cases."

Huang: It seems like it requires effort to become proficient at PHBP implantation. Do you feel like this is an important skill set to have for young implanters?

Sharma: Intuitively, PHBP seems to make the most sense physiologically. There is also a large amount of emerging data on the safety and improved clinical outcomes among patients with PHBP. In our initial paper, we demonstrated that patients with PHBP have improved outcomes in comparison to RV pacing. There is also promising emerging data on use of PHBP for CRT.

With an increasing amount of data on the success rates and improved outcomes with PHBP, I believe most device implanters should consider training on PHBP. It not only seems to be the best available way to activate the ventricles but it also adds an additional skill set to one's armamentarium. Particularly in patients with a failed coronary sinus lead for CRT, it gives an implanter another option before sending these patients for a surgical epicardial lead.

Huang: It seems counterintuitive to implant a lead into the His bundle when there is the level of AV block is infranodal. How robust is the safety and long-term data?

Sharma: We are learning more about the pathology and physiology of conduction system disease with PHBP and have realized that a fair amount of infra-nodal disease is possibly within diseased fibers in the HB and can be recruited as long as the lead is placed distal enough on the conduction system. Pugazhendhi Vijayaraman, MD, FACC, et al., reported their experience in a small series of patients with PHBP who returned for generator changes and demonstrated no evidence of progression in conduction system disease in medium term follow-up. In cases where there is any concern about the level of disease or disease progression, we have learned that trying to achieve non-selective (His + RV) pacing might provide more safety since we would still have RV pacing back-up. Occasionally, we might consider implanting an additional (back-up) lead in the RV.

Huang: What is the story behind #DontDisTheHis on Twitter?

Sharma: PHBP is the new kid on the block. Social media has been instrumental in helping us (the believers in PHBP) increase awareness and generate excitement about PHBP. #DontDisTheHis was the tagline for PHBP that Vijayaraman – the "Father of Modern HBP" and my original mentor – and the team at Geisinger Wyoming Valley developed when I was with them from 2011 – 2014. This hashtag has become our "tag line" on Twitter and other social media avenues. Most implanters are posting cases and their experience provides a forum for others to learn or share their experiences. Follow us on Twitter at @psharmadoc and use #DontDisTheHis.

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This feature interview was conducted by Henry D. Huang, MD, FACC, cardiologist at Rush University Medical Center, interviewing Parikshit S. Sharma, MD, MPH, FACC, electrophysiologist at Rush University Medical Center.