The next presentation is by Dr. Olojima Adjijola, and he's going to speak about indications for his bundle pacing, who and when. Good afternoon, ladies and gentlemen. It is really an honor to be here with you this afternoon to talk about who and when in terms of indications for his bundle pacing. And it's really quite an honor because the co-panel of speakers and our chair are legends in this field that have taught us a lot about his bundle pacing. Here are my disclosures and my funding sources. So I've been asked this afternoon to talk about indications for his bundle pacing, who and when. And actually, perfect, you can see my mouse. And, you know, I say this with a bit tongue-in-cheek when I say virtually anyone, especially if they have an increased pacing burden, and virtually any time. And my hope this afternoon is to show you some of the data that actually suggests that this is the case. Of course, keep in mind that we don't have guidelines that suggest this per se. But I think that there's enough data emerging that in experienced hands and in the right patients, you really could consider this as a guideline for indication for his bundle pacing. Specifically, I'd like to talk about just a couple conditions for his bundle pacing, his bundle pacing for cardiac resynchronization, which is one of my favorite reasons for doing his bundle pacing. His bundle pacing in the setting of heart block and AV node ablation, and for pacing-induced cardiomyopathy. Of course, no talk about his bundle pacing is complete without acknowledging the work of Dr. Ben Sherlag, who initially described this in a canine model. You see here that this is what the QRS morphology looks like in sinus rhythm. And with his bundle pacing, that looks identical to that. And with atrial pacing as well. And along with his colleagues, Nabil El-Sharif and others, showed that if you actually look in a patient where left bundle branch block is shown here, and you pace the proximal portion of the his bundle, you don't narrow the QRS. But if you pace the distal his bundle, that results in QRS narrowing. And this observation is, in large part, why we're all here today. Now, there have been quite a number of papers in between that and that that I'm showing here. But I'm just going to highlight a few papers, and that includes one here by Barbara Pichardo, where he moved this concept of narrowing the left bundle forward in 16 patients with left bundle branch block and dilated cardiomyopathy. And keep in mind, this is at the time of using active fixation leads, not the 3830 that most of us use now. And you can see very nicely that they took a very widened QRS with his bundle pacing that was narrowed. If you look at echocardiographic parameters, nice reduction in LA diameter and end diastolic dimension in addition to end systolic dimension, and a nice improvement in LVEF. And this work was extended by our session chair here, Dr. Lustgarten, and his colleagues, where they took a unique approach of a crossover design where patients were implanted both with a his bundle lead and a left ventricular lead. I'll talk about doing two procedures in one. And in that study, at six months, after the six-month time point, patients that were randomized to the his bundle were crossed over to BIV and vice versa. And his findings essentially showed that in this setting, CRT, as we think of it, with the LV lead and his bundle pacing were about equivalent, whether you look at ejection fraction, the patient's NYHA functional class, the quality of life, and the six-minute hall walk test. Our group moved this concept a bit forward by actually using his bundle pacing in lieu of an LV lead. And we did a small feasibility study at two sites where we recruited 21 patients, had five unsuccessful implants, and in total had 16 successful implants in our study. And if you look at the QRS narrowing here, nicely narrowed from 180 milliseconds to about 129 milliseconds, and that was concomitant with a very quite significant improvement in LVEF from a mean of about 27% to about 41%. In addition to that, there was also a reduction in NYHA functional class and reverse remodeling of the left ventricle in these failing hearts. And almost contemporaneously, Parikh Sharma and his colleagues, again, many of the speakers here today, took this concept even further forward in looking at many more patients, although their population did have patients where they similarly used his bundle pacing in lieu of an LV lead, but they also extended this to patients after a failed LV lead and a very nice-sized study with 106 patients. And if you look across their indications here, they had fairly high success rates of implantation, whether it was a rescue, his bundle pacing, for a failed IV, whether it was for non-responders, AV node ablation, et cetera. And their outcomes, similar to ours, were really quite nice. Overall shortening of QRS duration, about 157 milliseconds to 118, and whether that was bundle branch block patients or ventriculate pace patients. Very nice increase in LVEF, LV function. Overall, 30% to 44%. And whether you look at patients who had significantly reduced LVEF or patients who had moderately reduced LVEF, both groups benefited, both in terms of improvement in LV function and also their NYHA functional class. And there have now been actually two meta-analyses. I'm just going to show one here from Francesco Zanon, again, a lot of his co-authors on this paper are actually here on this panel or in this room today. And if you look across all the studies, I mean, he didn't just look at his bundle pacing for CRT. He also looked at patients who needed regular pacing. But you get the sense that this is increasingly used with high success rates. And if you look again across studies, nice improvement in LV function here, again, across the studies from about a mean of 23 to 50s to 33 to 60s. So suggesting, again, this is a very robust use for his bundle pacing. Now, Dr. Saxena talked about this a little bit, so I'm not going to go too much into it. But why does this happen? I think this is one of the most fascinating aspects of doing his bundle pacing is what is the physiology behind QRS narrowing? You see here one patient from our study that narrowed from 200 milliseconds to 112 milliseconds. And as Dr. Saxena very nicely pointed out, this idea of longitudinal dissociation has been thrown out for a very long time. This is the same paper from Ralph Lazara that he showed. And the concept here is that fibers that are going to the right bundle and the left bundle are predestined, such that if you had a block here, as shown here, these fibers, you would get right bundle branch block in this situation, but the left bundle would be fine. And perhaps by putting a his bundle lead in this region, you would recruit both bundles. And they supported that by others have shown sort of how potentially you can get fibrosis within the his bundle itself. But we're not so sure that this necessarily is the mechanism. It is also possible that, as he showed, these very nice fibers that could be sourcing mismatch in terms of getting conduction down the his bundle, again, yet to be proven. Now, I believe the next speaker after me, Dr. Apadia and his colleagues just published this very nice paper in a circulation where they showed, essentially mapped 88 patients or 88 patients with both the left and right side of the septum. And they didn't so much find split hisses, which may suggest longitudinal conduction. They saw a lot of proximal bundle branch block. And those are the patients that actually narrowed with his bundle pacing proximal block in the left, high up in essentially where the left bundle comes up. And potentially, this might be the mechanism by which patients can narrow. I imagine he may talk more about this. But the point here is just that the jury's out. I think that we still don't completely understand why it is that we're able to narrow the QRS substantially with his bundle pacing. Now, looking at another indication in right bundle branch block, that has also been done by Parikh Sharma and his colleagues. And if you look here, they had a total of, I believe, 39 patients that were successful in instituting permanent his bundle pacing in 95% of the patients. They narrowed their right bundle branch block from about 158 milliseconds to 127 milliseconds. And that was regardless of whether the patients were paced with an underlying right bundle branch block or not. They got very nice reduction. And you can see here a significant improvement. I think many of us would be happy getting our patients' LV ejection fractions up by these numbers that you see here. And improvement in functional class as well. So right bundle branch block, also a feasible and approachable for his bundle pacing here. So overall, shortening of the QRS duration and improvement in LV function overall, and both in patients with low ejection fraction and a higher ejection fraction as well. Now, often people are worried about instituting his bundle pacing in patients with complete AV block or patients that you're going to do AV node ablation in. And the concern's always, well, what if the lead dislodges and the patient has no underlying rhythm? That could be a big problem. So this paper very nicely addressed that, among others as well, where Poguel showed here the use of his bundle pacing at the time of AV node ablation. And showed the regions where he actually ablated to get AV blockade. And they're very close to the his bundle lead. And here's a fluoroscopic image of this, where you see the ablation catheter in pretty close proximity to either the distal or the proximal ring of the his bundle lead. And here's an example of a patient with AF, rapid conduction, and a cardioversion of that patient in his bundle pacing with a very, very narrow QRS. And if you look across their study, even at 19 months of follow-up, they still had essentially stable QRS narrowing in these patients, and the thresholds didn't rise substantially from 1 to 1.6, which is still within the means. Yeah, time? Yeah, okay, perfect. All right, and improvement in LV function from 43 to 50%. I just have one more study to show here, which is his bundle pacing for chronic AV block and pacing-induced cardiomyopathy, also from Pogal's group, very nicely here. And I think one thing that stuck out to me about this paper is that they took patients that had AV block for a long time and had been paced. For example, this patient, for 8 years, they were still able to narrow the QRS. This one, for 22 years of chronic pacing, and were still able to substantially narrow the QRS. And you look across their study here with very nice numbers. Now, the one thing just to say is that for those that are concerned about complete AV block and his bundle pacing, non-selective his pacing can serve as a protective mechanism where you still capture some of the local ventricular myocardium to prevent complete loss if you lose his recruitment. And the last point just to make is that we actually now have some guideline recommendations for the use of his bundle. I won't belabor this too much in the interest of time. And many ongoing studies. As of this morning, this is clinicaltrials.gov, 42 studies on his bundle pacing. So I think there's a lot more to learn and a lot coming. So I'll conclude by saying his bundle pacing is a reasonable option for many pacing indications. I've just shown some examples here. And this may be particularly true in patients with bundle branch block and depressed LVEF, now appearing in guidelines and likely to expand, and better understanding is absolutely needed and will take this forward. And with that, I'll stop and acknowledge my colleagues at UCLA. Thank you. Okay.

bundle pacing

cardiac resynchronization therapy

heart block

AV node ablation

pacing-induced cardiomyopathy