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EP Fellows Curriculum: Electrophysiologically Corr ...
Electrophysiologically Correctable Cardiomyopathie ...
Electrophysiologically Correctable Cardiomyopathies
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Thank You Rod and thank you Nishant. It's my honor and pleasure to talk to you today. I'm thrilled to have this opportunity and I look forward to sharing some insights about this condition with all of you. So the title of my talk is electrophysiologically correctable cardiomyopathies. One of the first questions I had was how do you spell correctable? Is it I-B-L-E or A-B-L-E? Turns out both are correct and so we'll go with A-B-L-E for now but as an aside that was an interesting thought I had. How do you spell correctable? So as I started to work and develop this talk I really wasn't sure if I was biting off more than I could chew or I was hanging on for dear life because the more I delved into it the bigger the topic seemed to be and so I'll be giving you some you know a google-eye view of the issue in some ways but I'll also go into some details that may not be well recognized. So I'll let you decide by the end of the talk if I have been successful in hanging on or whether it was a bigger bite than I should have taken. So here's the outline for our talk today. I'm going to define correctable cardiomyopathies and going to quickly go over the types, epidemiology, and history. We will then talk about the underlying pathophysiology which is I think very interesting and relatively new information. We're going to then talk about the two main categories. The first category being tachycardia mediated cardiomyopathy and we will touch on sinus tachycardia even when it is appropriate for example in its interaction with worsening heart failure. We'll talk about focal atrial tachycardias and double fire tachycardias. Just a couple of slides, one on each and then a few slides on atrial fibrillation and flutter resulting in rapid rates that can cause a cardiomyopathy. And then we'll talk about the second big category of correctable cardiomyopathies which is dyssynchrony mediated cardiomyopathy and that's really the bulk of my talk. I'm going to talk about left bundle branch block and I think you guys know all about left bundle branch block as a class one indication for CRT so I'm not going to delve on that but I'll share a couple of important or interesting insights that you may not be aware of. One slide on pre-excitation or right-sided pathways that can actually cause a cardiomyopathy because it mimics dyssynchronous activation akin to left bundle branch block. A lot of slides on frequent PVCs and pacing-induced cardiomyopathy. And that is really a summary because you can have an individual talk for a full hour on each of these two topics, PVCs and pacing-induced cardiomyopathy. And then I'll mention a few words about his bundle pacing how it is I think the ultimate resynchronization therapy. And then we'll end with some take-home slides. So with that definition with that outline let's get started with the definition. So what is a correctable cardiomyopathy? It's a condition in which atrial or ventricular rhythm or conduction disturbance can result in left ventricular dysfunction leading to systolic heart failure and the hallmark of this condition as far as we electrophysiologists are concerned is that it has partial or complete reversibility once the arrhythmia that causes it is controlled or the conduction problem that causes dyssynchrony is corrected. And as I said there are two categories. There's tachycardia-mediated cardiomyopathy and dyssynchrony-mediated cardiomyopathy. So let's talk a little bit about the epidemiology. Now the true incidence and prevalence are really uncertain because they are very under-recognized entities. We're only now beginning to understand how prevalent they might be and the more we study them the more prevalent they seem to become seem to be. So it really is under-recognized. Tachycardia-mediated cardiomyopathy is really a problem with heart failure patients and atrial fibrillation. That juxtaposition of two pathology pathologic entities is really bad news. AFib and heart failure and many patients with cardiomyopathy and atrial fibrillation have worsening symptoms and ventricular function mainly due to poor rate control or loss of atrioventricular synchrony. It's a bit of a chicken-and-egg situation. You don't know if the heart failure got worse and that's why they got AFib but once they get AFib their heart failure certainly gets worse. No question about that. And when it is due to SVT it is actually as you'll see more common in children. It is known to cause hydrops fetalis that is not the immune variety but due to tachycardia often seen with PJRT or the incessant form of reciprocating tachycardia. In adults it is less common for SVT to cause tachycardia-induced cardiomyopathy compared to pediatric populations. And then for this synchrony cardiomyopathy it is not as frequent as AFib and heart failure which is up to 50% but up to a third of patients you can invoke frequent PVCs as a contributor to cardiomyopathy that is otherwise not explained. And right ventricular pacing as you will see is also turning out to be an important contributor to this synchrony-mediated cardiomyopathy. What about the history? It's interesting to think back when this was first recognized. Long-standing tachycardia has been recognized as a cause of LV dysfunction for a long time. The first four cases were actually reported in 1913 by Gossage in four men with atrial fibrillation and rapid rates who developed unexplained LV dilation and heart failure and one experienced sudden death during exertion. And he writes here that on examination the heart was found to be dilated and the rhythm very irregular and he goes on to describe it. And clearly this was done before the age of spellcheck because you see he misspelled face and he said his fika were cyanosed rather than his face was cyanosed. But that typo has now become historical in 2000 sorry 1913 more than a hundred years ago. In terms of tachycardia-induced cardiomyopathy in utero that was first described in 1947 and Dr. Garvin was the first author and he reports that a woman at the end of her sixth month of pregnancy you know was found to have a very rapid fetal heart rate 200 to 250 beats per minute. The baby went on to get delivered but an x-ray film of the baby of the baby's chest showed cardiac enlargement mainly to the left of the midline. So back then again it was recognized that the rapid heart rate could have been causing the cardiomyopathy in the baby. And the concept of PVC-induced cardiomyopathy was first proposed by Duffy in 1998. So you see that we are coming to the modern era but it's not that long ago that this was even first recognized. And he had seven patients with more than 20,000 PVCs on a Holter and EF less than 40%. They were treated with amiodarone for PVC suppression. Five of the seven patients were suppressed and four out of those five had a significant improvement in functional status and ejection fraction and they concluded that suppression of PVCs can be associated with improvement of LV function in many patients who are presumed to have an idiopathic cardiomyopathy. So that's a little bit about the definition, the two main categories, the epidemiology and the history. Now let's come to the underlying pathophysiology. And in order to assess the knowledge level of our audience I've put together one question that I'd like you to please answer using your multiple choice questions. Nishant you will help me here. The pathophysiology underlying reversible cardiomyopathies involves A, defective fast voltage-gated sodium channel malfunction related to SCN5A mutations. B, defective potassium channel function related to the delayed rectifier current IKR. C, defective calcium channel function in the sarcoplasmic reticulum related to junctophyllins, whatever that is. And D, defective parasympathetic innervation of the ventricular myocytes due to postganglionic axon apoptosis. So I'd like you folks to please enter in your questions and let's take a look. And I'm watching the counters build up and it does appear that the majority of you have it correctly recognized. Nishant how long do we give before we declare the... It looked like it was closed there so let me share the results. You can see it I think. Yes I can. Can everybody see it? So the majority did get it right. It is due to calcium channel function defect related to junctophyllin. Okay so I'll ask Nishant to take that off. Do you want me to take it off or can you? Yeah it's off. It's still on my... Okay let me close it here. Maybe I can close it here. There we go. All right so now let's go ahead and look and see what this is all about. So the pathophysiology of reversible cardiomyopathies. Most of the data are actually derived from animal studies and dogs and pigs. And heart failure is induced either by sustained atrial or ventricular rapid pasting. And there are a whole host of changes that have been described. Hemodynamics you know in various manners have been studied. Structural changes have been reported in a gross level in terms of visual examination. Cellular or histologic changes have been reported. And neuro hormonal changes have been reported. So a whole variety of changes have been reported to occur in the setting of these animal models with rapid pacing induced cardiomyopathy. And many of these changes are not unique to a tachycardia myopathy but are seen in other forms of heart failure as well. So it's quite likely that they're related to the downstream effects of heart failure, high feeling pressures, decreased cardiac output, rather than to the tachycardia itself. Talking about the neuro hormonal pathophysiology, again lots of pacing data from animals. It shows a predictable time-dependent change in neuro hormonal pathways with a change in synthesis and release of some bioactive peptides. And they are all listed here. And I'll point your attention to the last line, calcium overload of the sarcoplasmic reticulum leading to contractile dysfunction. That is a very key finding. These changes in neuro hormonal pathways likely reflect changes in the LV status from compensated to decompensated. And it's possible that these neuro hormonal biomarkers can be used to assess the progress and the status of a tachycardia-mediated cardiomyopathy. But again, calcium overload of the sarcoplasmic reticulum is key. And let's look at the mechanism by which that might occur. Calcium overload and defective calcium cycling leads to defective excitation-contraction coupling. I'll discuss this with you in more detail in a moment. And myocyte contractile dysfunction results with decreased inotropic responsiveness. This blunted contractility then results in LV dilation, lengthening and slippage of myocytes. There's actually changes in the extracellular matrix that occurs before there is change in the myocyte itself. And then this pro-apoptotic cascade is triggered that reduces cell viability, eventually leading to scarring. So this is this gradual vicious cycle that just perpetuates. In the animal model, it seems to occur much more rapidly than it does in human clinical scenarios. So what is the role of rate versus dyssynchrony in animal studies? You can study it quite readily. You can do rapid atrial pacing and ensure one-to-one AV conduction with a narrow QRS. And that would be a pure tachycardia cardiomyopathy because there's no dyssynchrony as long as the QRS remains narrow. Or you can do rapid right ventricular pacing, which then increases the rate plus gives you intraventricular dyssynchrony. And they show that there's more rapid onset of cardiomyopathy and a more precipitous drop in ejection fraction. So clearly adding dyssynchrony to tachycardia makes matters even more worse. But there is a lot of limitation to this data. The time course, as I mentioned, for development in animals is much quicker. In humans it can be months to years. And some arrhythmias can have mechanisms that are different and not fully explained by just rapid pacing and dyssynchrony or rapid pacing without dyssynchrony. So now that brings us to this important concept of junk to filin and how they represent the molecular underpinnings of correctable cardiomyopathies. What are junk to filins? They are a conserved family of proteins that are seen in all excitable, electrically excitable cells. They are important in maintaining that subcellular architecture that facilitates calcium signaling by providing close coupling of the cell surface to the intracellular sarcoplasmic reticulum channels. I'll explain this to you further. In myocytes, junk to filin 2 serves as a dyad or a coupling protein between the sarcolemma and the transverse tubule and the sarcoplasmic reticulum. So you may remember from your basic electrophysiology that the L-type calcium channel resides deep in the transverse tubule and it is directly opposed to the head of the sarcoplasmic reticulum which is then responsible for releasing calcium via the ryanodine receptor. And junk to filin is the protein that holds this association closely. It's a mechanical scaffold that makes sure that this L-type calcium channel is directly opposed to the ryanodine receptor at the head of the sarcoplasmic reticulum. It is a central mechanism that you have a calcium induced calcium release. That is, one ion of calcium coming in from the extracellular space causes a flood of 10 ions from the sarcoplasmic reticulum and then that calcium affects the sarcoplasmic reticulum, sorry, the sarcomere itself. So one ion of calcium comes in and you see that ion coming in yellow and then you can see a whole flood of calcium coming out which then interacts with the sarcomere. The calcium then floods the contractile apparatus. It causes troponin-tropomyosin configuration change which then exposes the actin heads which then interact with the myosin chains and you have contraction and systole. That entire process hinges on the correct apposition of the L-type calcium channel to the ryanodine receptor and that is maintained by junctophyllin 2. So this junctophyllin 2 is the anchoring dyad that makes sure that this coupling is always there. What happens in heart failure? It's very interesting. Isolated ventricular myocytes from transplanted hearts show that there is this t-tubule loss and disorganization that occurs in advanced heart failure which contributes to dis-synchronous calcium release and impaired contraction. T-tubule remodeling can be seen under the electron microscope in response to rapid rates, dis-synchrony, pressure overload, or infarction. From a tubular structure it becomes a sheet-like structure and this t-tubule reorganization then alters the spatial configuration or relationship between the L-type calcium channel and the ryanodine receptor. Junctophyllin is disrupted. Orphaned ryanodine receptors result in fewer dyads and less calcium release. Normally in health there is a nice lining up of these transverse tubules coming in from the cell surface near the sarcoplasmic reticulum but once you get remodeling then this transverse tubule becomes flat or sheet-like. There are some ryanodine receptors that are not directly opposed. The junctophyllin is orphaned and if you can reverse the problem at this stage it is still correctable but if you let it get to this stage it may be no functional recovery. So time is of the essence here in doing this correction early on. And here is actual electron microscopy in health and in heart failure. And in health you can see that the sarcoplasmic reticulum has these nice little thin transverse tubules that come in from the surface and they are very thin and tubular but in heart failure they become flat and transverse. They are malopposed to the sarcoplasmic reticulum. So this is an actual physical disruption of the structure of the subcellular apparatus that results in a disconnect and inefficient calcium release. In addition to t-tubule modeling there's also downregulation of the mRNA that controls the production of junctophyllin-2. And that leads us to the role of junctophyllin in a canine study. They actually did a study where they mimic frequent PVCs by right ventricular pacing protocol and they showed that there was a marked downregulation of junctophyllin-2 and this destabilized the t-tubules as we have discussed and resulted in a drop in ejection fraction. And now they are thinking that if we can restore junctophyllin-2 expression even in the face of continuing dyssynchrony you might be able to reverse the cardiomyopathy. And so they are now doing studies on gene therapy with a knockout gene that can restore dyad function in canine models of dilated cardiomyopathy and we await the results. So you might have a gene therapy based on this bench understanding. So this is another wonderful example of bench to bedside translation of our understanding in treating our patients. What is the time course? I've already alluded to that. In animals it's much faster. You can see that the effects on filling pressures and so on plateau within a week. In an animal model cardiac output EF and cardiac volumes continue to worsen for the next three to five weeks and within 48 hours of cessation of pacing things seem to get better back to baseline levels in control animals but that is not the case in human heart failure. And in animals EF normalization usually takes less than four weeks but we know that in humans it may take many months. Okay so that brings us to our next section which is tachycardia mediated cardiomyopathy and before I ask you before I tell you more about that let me pose you another question. Which of the following statements is true regarding tachycardia mediated cardiomyopathy? A. Restoring AV synchrony in patients with atrial fibrillation and heart failure is superior to rate control even when comparable heart rates are achieved by both strategies. Tachycardia cardiomyopathy is usually seen with ventricular rhythm disturbances and is uncommon with atrial tachyarrhythmias. Unlike atrial fibrillation with rapid ventricular rates sinus tachycardia focal atrial tachycardias and other regular SVTs are not associated with tachycardia mediated cardiomyopathy. And the results of the CASEL-AF trial which I'm sure you're all conversant with are inconsistent with prior meta-analyses of trials in similar patient populations. So let's see let's have a vote and once again I see that the vast majority are getting the correct answer that is regression to the mean. Majority wins. Okay so A is in fact the correct answer. It is true that restoring AV synchrony in patients with heart failure is superior to rate control even if you achieve comparable heart rates with sinus rhythm and continued AF and rate control AV synchrony helps. Okay very good so with that let's move on and take a closer look at some of this data. We quickly go over the SHIFT trial. This is a trial that was published almost a decade ago now and in fact a decade ago and it looked at the effect of slowing heart rate in heart failure patients with this medication IVABridine which is a specific sinus node sorry sinus current inhibitors IF inhibitor and they included patients with heart failure and heart rates at rest that were greater than just 70 beats per minute. Not very you know high threshold there and who had been on stable guideline driven medical therapy including beta blockade and they had about 3,000 and 3,000 patients randomly assigned to IVABridine or placebo and their primary endpoint was a composite of death or worsening heart failure and the primary endpoint was seen in 24% of IVABridine versus 29% of placebo an absolute risk reduction of 5% not a relative risk reduction relative risk reduction was much greater and the outcomes were driven mainly by reducing heart failure admissions but also reached statistical significance for death due to heart failure 5% versus 3% and they concluded that heart rate reduction with IVABridine improved clinical outcomes in heart failure and it confirms the important role of elevated heart rate in the pathophysiology of worsening heart failure in spite of optimal guideline driven medical therapy. So even when sinus tachycardia is quote-unquote appropriate to the level of heart failure slowing the heart rate seems to help. I think this is a an important point it is very often overlooked that patients may be at heart you know on a maximal therapy including tolerated beta blockers heart rates of 80 to 90 beats a minute on average and they could benefit from further heart rate slowing by medication that has no negative inotropic effects. Let's move on to focal tachycardias as a cause of tachymyopathy. Has that been reported? How often does it occur? Yes it has. In this study of 330 patients who underwent atrial ablation for focal tachycardias in the atrium there were 10% who had an EF of less than 50% and the others were normal EFs and LVF recovery was also assessed and they showed that the ones who had tachymyopathy tended to be more often male and they were younger compared to the patients who did not get tachymyopathy or didn't present with tachymyopathy and actually the people who had tachymyopathy had very incessant and frequent tachycardia which meaning that they had a higher burden of the arrhythmia and they actually had slower heart rates during tachycardia 120 beats versus 150 but it was very incessant and after successful ablation 97% of the patient normalized their ejection fraction in three months so they concluded that tachymyopathy from focal atrial tachycardia occurs in about 10% of such patients those patients tend to be male they tend to have slower tachycardias and ablation restores EF to normal so don't think SVT can't do it it can it's just not as common it's much more common in children these were all adult patients we had reported on a very interesting a double fire tachycardia as a specific manifestation of dual pathway physiology where one sinus impulse results in two QRS complexes the first goes down this fast pathway the second goes down the slow pathway and this is the electrocardiogram from that patient on telemetry there were frequent bouts of this sort of arrhythmia and you can see that the P waves march right through but some P waves are associated with two QRS complexes down this fast and down the slow and eventually the fixed conduction stops and it goes back to one-to-one conduction only for it to recur an ablation of the slow pathway reverses the myopathy and improve the ejection to norm how about atrial fibrillation and cardiomyopathy again we have information about the prevalence of AF and rapid rates as a cause of irreversible heart failure 104 consecutive patients without heart disease were hospitalized with AF and HF and about 60% had reduced ejection fraction whereas 40% had preserved ejection fraction off this 60% about half showed normalization of the EF within six months after treating atrial fibrillation in other words after restoring sinus rhythm about half of these patients with reduced EF normalized their EF the other half showed persistent reduction in EF even after restoring sinus rhythm and they concluded that in patients with heart failure and atrial fibrillation tachymyopathy is the cause of heart failure in approximately one-third of all patients since about 30% or 40% actually have preserved EF to start with so again not uncommon but the problem is it's hard to identify this is a retrospective look at after outcomes were achieved prospectively you don't know which patients are going to get better after you get rid of atrial fibrillation so I think the bottom line is you have to try here are some additional summary data I had a whole bunch of slides that I just summarized into one slide here's a study that looked at 659 patients of which about 10% had tachy due to AF and rapid ventricular rates and they showed significant improvement in all parameters after AFib ablation this was a meta-analysis of 19 studies with a 914 patients and they had a similar outcome at the end this is another meta-analysis of six patient six studies with 324 patients catheter ablation of AFib with reduced EF improved EF functional capacity and quality of life compared to rate control even though rates were comparable in the two groups so AV synchrony certainly matters in heart failure and another meta-analysis essentially showed the same results improve quality of life exercise capacity after ablation compared to medical therapy for atrial fibrillation and rate control so the bottom line is that in heart failure restoring AV synchrony restoring sinus rhythm matters it makes a difference so whenever it's feasible to do so you should contemplate doing so and this was way before we had Castle AF and now with Castle AF this has been consistent with all these previous data in that the death or hospitalization from heart failure is improved by catheter ablation compared to with medical therapy so again whenever possible whenever appropriate when the atrium is not terribly diseased when the heart failure is not to end stage offer rhythm control strategy and in those settings usually it's ablation that's the winner rather than medical therapy okay and that brings us really to the bulk of our talk which is dyssynchrony mediated cardiomyopathy and we'll start with left bundle branch block just a couple of slides there because you guys all know about left bundle branch block but before I do that let's ask you a question so regarding dyssynchrony mediated cardiomyopathy which of the following statements is correct a patients with new onset dyssynchrony cardiomyopathy due to left bundle branch block should undergo a three-month trial of guideline driven medical therapy prior to consideration of CRT B uncontrolled hypertension equally affects patients with left bundle or narrow QRS as long as they have a low EF hypertension is equally bad for both sets of patients low EF and left bundle and low EF with narrow QRS C epicardial PVCs are less likely to result in a dyssynchrony cardiomyopathy compared to endocardial PVCs D the percentage of right ventricular pacing associated with the development of dyssynchrony mediated cardiomyopathy is greater than 50% in other words you have to have a fair amount of RV pacing before you are at risk of developing this cardiomyopathy and E all of the above statements are false so let's take a look and see dr. Poverty maybe I'll use this as a break to ask a couple of questions have come through certainly do you have any either clinical or echo parameters that you would use to say that a cardiomyopathy is irreversible and maybe not worth the effort of an ablation so that's a very good question but it's a very difficult one to answer with very little data the data we that I am aware of talks about looking for scar by late gadolinium enhancement on MRI so if you get an MRI and you see a boatload of scarring that cardiomyopathy is not going to improve it is very unlikely that it will improve but however if you see very little or no scarring those are the patients that tend to get better the most I will go over some of the specific clinical features that are more likely to result in a cardiomyopathy and but again there's no real data that identifies which of those patients are most likely to reverse the cardiomyopathy it's usually a matter of catching the patient before irreversible damage has occurred before that irreversible slippage of the transverse tubules and the sarcoplasmic reticulum alignment has occurred before that results in apoptosis and scarring so the sooner you jump on the patient the better off you are and I'll tell you one of the clues on the ECG that a left bundle branch block is relatively recent in onset is very underappreciated we are actually able to recognize new or recent onset left bundle from long-standing left bundle branch block and that relates to the height of the T wave if the precordial leads show very tall T waves that is a recent onset left bundle branch block morphology if the T waves are of low amplitude and flat even though the QRS complexes in V1 through V3 are deep and narrow I mean deep and tall that is a long-standing cardiomyopathy so the height of the T wave clues you in to new onset or recent onset left bundle branch block and that would be a clue that this might be reversible as well. I don't know if you have any additional thoughts to add Nishant or Rod. No that was great the other question that came through you may get to in the next section but you know people are asking for patients that are asymptomatic but with a high burden of PVC's how hard do you have to push to push treatment in terms of ablation or drugs? Yes I will answer that in later in the talk when we get to the PVC portion I actually have that area addressed specifically I will get to that. That's what I thought and I put the poll results up for you there. Okay so I'm actually surprised that I thought that it would be a no-brainer the way I had worded it everybody would go for E which is the correct answer but a substantial number actually looked at A favorably so let's take a look and see why A is not the correct answer actually. All right so let's go on now and see what we can learn from this. I'm glad I put up that question first so let's quickly go over left bundle branch block. You guys all know this here's a meta-analysis of CRT trials and you know that if you have a classic left bundle branch block pattern then you know that the ejection fraction improves survival is better everything gets better with CRT but if you have a non left bundle wide QRS complex then that is not the case. So when you have classic left bundle branch block which meets all the correct criteria for left bundle branch block CRT is definitely the way to go and you should actually offer it as soon as you can. So let's take a look at this data now. This was us every once in a while I come across a paper that I think is very important but seems to fly under the radar and is not may not be as well recognized or picked up. I think this was one of such studies. They looked at new onset left bundle branch block and idiopathic cardiomyopathy and the response to guideline driven medical therapy and they called it the Neolith study and the question was in patients with new onset left bundle and cardiomyopathy that is recently recognized in other words patient that was known to have a normal EF and a narrow QRS and now they present with heart failure low EF and left bundle. What is the response to guideline driven medical therapy versus CRT? So these patients had an EF of less than 35 left bundle or narrow QRS and they looked at a hundred and two such patients 70 with narrow 32 with left bundle all got guideline driven medical therapy and post therapy EF increased in 56% of patients within three months of GDMT with a narrow QRS but only in 6% of patients with the left bundle and after CRT all of the left bundle patients showed improvement in EF and a super response to near normalcy was seen in 8 out of 32 patients. So they came to the conclusion that three months of guideline driven medical therapy did not improve EF in any significant manner if you are convinced that this was new onset left bundle and a new onset cardiomyopathy and CRT actually was the right thing to do and offered a higher rate of super response. This data has since been confirmed. Here is a more recent publication and they looked at this was a retrospective study but they wanted to answer the question do these patients with left bundle and cardiomyopathy adequately respond to medical therapy as compared to other QRS morphologies and they looked at the Duke echo database so many important papers have come out of that huge database that they have. They identified patients with low EF and our follow-up EF after three to six months and the QRS morphology was classified into three groups left bundle non left bundle wide QRS or narrow and they compared the change in EF with they adjusted the change in EF for other comorbidities and therapy that the patients received and they had a total of 659 patients 111 with left bundle 59 with non left bundle wide and 489 with narrow and you can see that with guideline driven medical therapy 2% showed an improvement in ejection fraction but the actual increase in ejection fraction was 2% in that group whereas the increase in ejection fraction was 8% in the narrow complex group and intermediate in the non left bundle wide complex group and they concluded that GDMT results in no significant increase in EF in patients with cardiomyopathy and left bundle non left bundle wide QRS show some benefit the greatest benefit for medical therapy is derived in patients who are already synchronous to begin with. It highlights to you the profound impact of dyssynchrony on the failing ventricle. Dyssynchrony is bad news. This beautiful narrow QRS complex that nature has provided us with perfect synchronized activation of both ventricles is a wonderful thing and when possible should be restored or preserved. Okay let's look at the response of left bundle branch versus narrow QRS in the face of increasing afterload. So how does uncontrolled hypertension affect patients with left bundle branch block? They looked at 11 asymptomatic patients with isolated left bundle and 11 age match controls with narrow complex. Systolic blood pressure was raised artificially by pneumatic extremity compression and isometric hand grip and they then did a study on eight anesthetized dogs in whom they implanted left ventricular micromanometers and dimensional crystals to look at the deformation and the function myocardial work of the left ventricle. And in human patients the controls raising the systolic blood pressure by 38 millimeters caused the EF to drop from 60 to 54 if the narrow QRS but in left bundle it went from 56 percent to 42 percent. And in the dog model the bending of the aorta was done to afterload increase the on the left ventricle and they created left bundle branch block surgically and they showed that when they elevated the blood pressure the septum made no contractile contribution to LV global work and instead it absorbed energy from work done by the LV lateral wall. And they concluded that even a moderate increase in blood pressure can cause a marked decrease in injection fraction in the setting of left bundle branch block and cardio depression of the dyssynchronous LV due to loss of septal function. So again highlights the impact of dyssynchrony when it is when the failing ventricle has to deal with a higher afterload just can't handle it if it's not synchronous. That brings us to one slide on pre-excitation. After all right sided pathways cause left bundle branch block like activation. The RV activates first. This was a study in 10 children. They had no incessant SVT so this was not a tachymyopathy. All had right sided pre-excitation and everything else was normal in those hearts and they showed that eight patients were ablated. Two patients had spontaneous loss of pre-excitation and injection fraction improved in all of these patients after loss of pre-excitation and they concluded that right sided accessory pathways and the resulting LV dyssynchrony can cause a dilated cardiomyopathy that reverses after loss of pre-excitation. Dr. Pavri before you move on can I ask a couple questions about dyssynchrony? Of course. One was whether you think there's a role for CRTP in patients who have an EF of 35 to 50 percent and does the location and extent of LV dyssynchrony predict outcomes for CRT patients? So yes I'll answer the first question later on in the talk. There is a little bit of information about that but regarding the second question I'm not really aware of any good studies that have definitively shown that dyssynchrony in a certain portion you know is more likely to respond as detected by echo. These echo tissue doper imaging studies and strain imaging studies are frankly beyond my level of comprehension as a dumb electrophysiologist and I am not able to answer that question in an informed manner so I think you should probably consult with somebody who knows more about than I do. Do you guys have any insights Nishant or Rod or anybody else for that matter? No I don't. Okay all right so let's go on and talk about frequent PVCs. So PVCs and cardiomyopathy are a well-established association and although considered generally benign epidemiologic studies from Framingham to Mr. Fit to Eric have all consistently shown that patients with PVCs have a worse prognosis and a higher morbidity and mortality compared to patients without PVCs. Now diagnostic evaluation for a patient with PVC should include as you know a complete family history and a personal history, a physical exam, 12 excuse me ECG, Holter monitor, echo and advanced imaging with a treadmill, cardiac MRI, endocardial voltage mapping to exclude structural heart disease. So you really need to characterize these patients before you declare them as being you know structurally normal hearts. And the management options are watchful waiting if asymptomatic with a normal EF with annual evaluation, medical trial with beta blockers, calcium blockers and antiarrhythmic drugs but they are rarely effective and then catheter ablation which has clearly been shown to be superior to medical therapy and often curative if the patient has a cardiomyopathy that you think is due to frequent PVCs. So once again it's a matter of timing, you're not sure what came first, sometimes in clinical practice it's impossible to tell as long as you don't see a lot of scarring by MRI you go ahead and offer them an ablation and you wait and see does the EF get better or not if you're able to successfully ablate them. So here's a meta-analysis of PVCs and their relationship to cardiac mortality in the general population published in 2013. They looked at 11 studies and a total of 106,000 patients and the bottom line was that sudden death was higher in patients who had frequent PVCs and total mortality was higher in patients who had frequent PVCs and this was after adjustment for all other conventional risk factors for these outcomes. So there's no question that these PVCs do contribute to bad outcomes. So you know our clinical practice is that if a patient has a structurally normal heart and they're asymptomatic if they have frequent PVCs you leave them alone. That's probably still true but I want you to understand that these these subtle changes that occur can only be picked up by long-term follow-up you know the mortality over decades or a subtle drop in ejection fraction that may contribute to slightly less longevity. That kind of subtle impact is going to be hard for most clinical datasets to pick up and you'll have to depend on population-based studies or meta-analyses to pick up that kind of subtle effect. So yes if you have a low EF or if you're symptomatic it's a no-brainer but the question remains somewhat unanswered what to do with a truly asymptomatic patient who has a truly normal ejection fraction but has a very high ventricular burden of ectopy. This data that I'm showing you would suggest that those patients ought to be offered ablation but it has not yet made it into the official guidelines. It's certainly not a class one indication for ablation. Now let's look at factors that influence the propensity to developing a cardiomyopathy with PVCs. Certainly the frequency and burden ectopy overall matters. The number of PVC morphologies has been shown to make a difference. The coupling interval whether they're interpolated or followed by a compensatory pause that seems to affect the risk of developing a cardiomyopathy and interpolated PVCs may be bad news. PVC width, the width of the QRS complex during the PVC matters. The site of origin reflects directly for the width of the PVC so these are sort of the same idea and the duration of follow-up. How long do you follow a patient actually increases the yield of your concern in the sense that more patients when followed over a longer period of time may show the development of a cardiomyopathy. And then the question is does ablation work and I think you know the answer to that one. Yes it usually does but not in everybody. So let's look at frequency and outcomes. How do you define frequent PVCs? Guess what? As long as you have more than one PVC on a 10-second ECG that's frequent PVCs. One PVC translates to about 8,400 a day if you do the math. More than one PVCs is somewhere above that number and that is considering that we usually have between 80 and a hundred thousand heartbeats a day. That's upwards of 12% of PVCs if that 10-second ECG is representative of the rest of the day. So the question is is it? Yes it turns out it is. Many studies have used a spot ECG for PVC assessment and then correlated it with a 24-hour holter. And the sensitivity and specificity for high burden on a holter from a single ECG showing more than one PVC is 74 and 94 percent. So it's not bad when you see more than one PVC on a resting ECG. Think about frequent PVCs occurring and get a holter. However it's also true that there is tremendous day-to-day variability in ectopy burden and multi-day holters have reported a doubling from the lowest to the highest daily PVC counts. So this is sobering. If you get a 24-hour holter on somebody where you suspect the tachycardia mediated cardiomyopathy because you saw some PVCs on the ECG and the holter reports you know 5% ectopy. If you are convinced that there's no other cause, don't dismiss that as a possibility. You might want to repeat a holter. Which is why I typically get a longer day recording. I get a four or seven day holter. Today's patch monitors are very easy to use. They're not cumbersome and inconvenient. And then I look at the daily burden of ventricular ectopy. Not just the average but the day-to-day burden and make sure that there's no single day where it's clearly much higher. That kind of patient may potentially have a PVC mediated cardiomyopathy. And then there's data about the consistency in hourly PVC frequency throughout the day. PVCs that occur mainly at night for example are different from patients who have PVCs throughout the day. Nocturnal PVCs may be benign. PVCs that occur throughout the day may be more likely to be associated with cardiomyopathy even though the total PVC count may be the same in the two sets of patients. How about the width and coupling interval? Here is a study of 1,500 patients and they broke them into low, moderate, and high PVC burdens depending on the number of PVCs per 24 hours. And the high PVC burden was associated with the lowest ejection fraction. And you can see that with each quartile the EF drops and the LVN diastolic volume increases. And the wider the QRS the lower the survival rates and worse the ejection fraction. And you can see that with wide PVCs the EF dropped more compared to patients with narrower PVCs. So the PVC duration is also important. The width of the QRS interpolated PVCs were more likely to cause a cardiomyopathy in this study. A little bit more about the PVC duration and site of origin. In 294 patients Yoko Kawa et al described that frequent PVCs that were referred for ablation they measured the QRS duration and the ejection fraction and they basically came to the conclusion that the broader PVCs had an epicardial origin and they were more likely to be associated with the development of cardiomyopathy. Fewer epicardial PVCs are required to cause a cardiomyopathy. In other words, look at this last line here. Threshold PVC burden for developing a cardiomyopathy was lower in patients with a narrow PVC versus a broad PVC. So you needed only 22% if you had a PVC duration greater than 150 versus a higher burden of ectopy if you had a narrower PVC. So I think this is again offers you some insight into the dyssynchrony that is being imposed by these PVCs. Obviously the wider the QRS the longer it takes the two ventricles to get depolarized the more dyssynchronous they are. How often does cardiomyopathy develop and how long does it take? We've already alluded to this but in this study of 239 patients structural heart disease was excluded and they followed them for almost five and a half years and there was a significant inverse correlation between the PVC burden and the drop in EF and a positive correlation between the burden and the increase in LVN diastolic dimension and 5.5% developed a drop in EF and PVC burden and initially EF were independent predictors. EF worsened steadily with time and so you can see how the EF starts to drop in everybody over time and the LVN diastolic volume increases in those patients in those 13 patients. So you realize that even when it's dropped it's still in the narrow in the normal range right it's going from 80 to 70. You wouldn't call this a cardiomyopathy you would ignore it. So that's what I was referring to earlier when I said that these subtle changes in EF that occur over extended period of time may not immediately translate into bad outcomes and you will need population-based studies and large data and long follow-up to really recognize this impact of a minor reduction in EF. But the bottom line is that frequent PVCs are associated with worsening of left ventricular function and size and then there's data about sudden death and total mortality as well. Okay so conclusion the prognosis in patients with frequent PVCs is usually benign because none of them during that 5.6 years had any serious cardiac events but EF does drop and it is especially true if the baseline PVC burden is high and those are the patients that need careful follow-up. So here's a meta-analysis of whether ablation works. You have lots of studies including lots of patients and the percentage of patients who improved ranges anywhere from 60 to 100% and the ejection fraction improves in anywhere from 55 to 100% of patients who are offered an ablation and so yes ablating frequent ventricular ectopy does help but not everybody. Success rate varies a lot for the procedure. It depends on the operator experience, the modalities used, and the location of the PVC. As you know crest PVCs from the crest of the interventricular septum and epicardial PVCs in general have a lower success rate compared to endocardial PVCs. So that brings us to pacing induced cardiomyopathy and let's talk a little bit about that. This is a study of 800 plus patients who received a pacemaker for complete heart block and started out with a normal EF and a pacing induced cardiomyopathy was defined as need for upgrade to CRT with the drop in EF of less than 40% and the response was defined as an improvement by 10% or a drop in LDN diastolic volume. 12% developed a pacing induced cardiomyopathy over four years and the post pacing EF was 34% in those patients. Multivariable analysis showed that RV pacing percentage greater than 20% had a 6.7 fold increase in risk of developing a pacing cardiomyopathy and overall when they got an upgrade 84% responded but only 45% actually got an upgrade. So they said that pacing induced cardiomyopathy is common. It is associated with as little as 20% RV pacing and CRT response rate is high but is underutilized. We have similar data from other studies as well. I haven't included all the studies out there. What are the ECG factors that are associated with pacing induced cardiomyopathy? Here's 1,700 patients and they looked at patients who had more than 20% RV pacing and they defined a cardiomyopathy in a similar fashion and they showed that the wider the paced QRS duration was the more the risk of cardiomyopathy development and a paced QRS duration greater than 150 milliseconds was 95% sensitive for the development of a cardiomyopathy and all it needed was 20% pacing. So once again you know 150 milliseconds with a paced QRS, that's very common. How often do you see RV pacing with a QRS complex that's more than 150? Practically all the time. So all it takes is 20% of pacing and you are at risk of developing a cardiomyopathy. What ECG factors again? Another study, 194 patients, they divided them into three groups with a paced QRS duration that was very broad, more than 190 between 160 and 190 and less than 160 and they showed that in patients who had these very wide QRS complexes they had the worst prognosis. So a wider paced QRS duration has a detrimental effect on long-term cardiac function with RV apical pacing. All of these leads were in the quote RV apex but I put it in in quotes because very often radiographic impression of a right ventricular apical lead location is actually incorrect and CT scans and MRIs will show you that the lead is actually on the free wall near the apex but it's not on the septum or it's on the inferior wall, it's not really at the apex of the right ventricle. So the wider the QRS, the worse the prognosis with RV pacing, RV apical pacing. So what about non-apical sites? So yes there's again lots and lots of data. I'm just showing you a little summary here. There were three locations in this study apex, outflow tract, and inflow tract and this was precisely determined by right and left sine ventriculography at the time of pacemaker implantation and they showed that there was a significant narrowing if you put the lead on the septum. The septum had the narrowest QRS complex. So this would be the RV apex, this would be the septum, and this would be the RV outflow tract and the septal sites are the ones that have the narrowest QRS complex and there's a clear relationship between pacing site and the width of the QRS complex with pacing. Now does trying to get a narrow QRS result in less left ventricular dyssynchrony? In other words if you can find a site that has a narrow QRS will you get less dyssynchrony? Yes indeed you do. I always do this double curve. This is a stylet that I have shaped with two curves to it and there's a secondary curve that points it to the septum and using that stylet you can reliably get to the septum in the majority of patients and that does give you the narrowest QRS complex of all and in this study they actually did intraoperative echo with pacing at different sites and they showed that with tissue Doppler and M mode that the least dyssynchrony was noted when the lead was on the septum and not on the free wall. And the QRS duration of course was narrower on the septum as well and so yes a narrower QRS obtained from the septum translates into less LV dyssynchrony. So you should think about not using the apex. You should think about using the septum for your pacing site. Now just like with left bundle branch block we decided that medical therapy is not very helpful if the left bundle is indeed responsible for the cardiomyopathy. The same question can be posed for pacing induced cardiomyopathy. Does pacing induced cardiomyopathy respond to guideline driven medical therapy? And the answer is unfortunately no. That these patients do not respond to guideline driven medical therapy. You need to upgrade them to CRTP and it improves EF. And that's where CRTD does not seem to make a big difference. There is really no major advantage. The majority of these patients actually do get better. One way to assess that again is to look at pre-upgrade MRI and if you see very little late gadolinium enhancement that's the kind of patient who's likely to improve their EF significantly. If you see a lot of late gadolinium enhancement they have substrate that is fixed and there you might want to think about upgrading them to a defibrillator. Okay so this is the question upgrade to CRTP or CRTD and in this study with 199 patients they showed that CRTP was really as good that there was a only three patients who died from primary arrhythmic death in the CRTP group and there were no rhythmic deaths in the CRTD group obviously but there were 32 other deaths. And so this non-significant small difference in mortality was really accounted for by non-sudden death and women were at especially low risk of sudden death versus men. So especially in women you're pretty good if you don't have a lot of MRI to just upgrade them to a Bi-V pacemaker or CRT pacemaker. I hesitate to say Bi-V in today's day and age of his bundle pacing and left bundle area pacing and I'll get to that in a moment but really a defibrillator should be carefully thought off it's not necessary for everybody. CRTP may be enough. And that brings us to his bundle pacing which in my humble opinion is the ultimate resynchronization. Look our beautiful His-Purkinje tree has evolved over millions of years of evolution. This is the same model that is present in mammal on the planet and it achieves this perfect systole the squeeze of the left ventricle but perfectly timed delivery of electrical activation. We'll talk more about that. How is it possible first of all to recruit the left bundle branch if it's blocked by pacing the bundle of His? After all left bundle branch block implies there's disease below the His, correct? In the left bundle branch. How can pacing above the left bundle in the His bundle recruit a blocked left bundle or is this our correct understanding? Actually the truth is that in 70% of patients the left bundle branch block pattern is most often due to disease in proximal His bundle fibers that are predestined to travel to the left bundle. In other words these His fibers show longitudinal dissociation. They don't conduct side-to-side but they're all about rapid propagation in the anti-grade direction and pacing distal to such a disease site still in the distal common bundle of His can be distal to the disease segment and can recruit the left bundle branch block pattern. So here's how it works. So here is a schematic of the AV node His bundle and the right and left bundle branches and the fascicles. And the concept is that there are fibers that are committed in the His bundle to travel to one or the other side. They show very poor side-to-side communication but excellent longitudinal communication. If you see a left bundle branch block pattern in lead V1 you expect that the disease is out there, correct? It's not. In 70% it's out here proximally but in fibers destined to travel to the left side and therefore when you pace the common bundle of His in a more distal location you can capture the whole bundle and narrow the QRS complex with His bundle pacing. So this is the simplistic explanation. It probably has more to do also with the higher output that we deliver through artificial pacing compared to the low microvolts that are delivered by native propagation and how you might be able to overcome disease if there is a higher output. So here's an example of a patient with atrial fibrillation right bundle branch block and rapid response. You can see the right bundle branch block here in a white QRS. We did a His bundle pacemaker. Back then I was putting in a backup right ventricular lead because I wasn't sure how good I would be with His bundle pacing and this is the backup RV lead chronic AFib so I connected to a dual chamber pacemaker, kept the AV delay long, put the His bundle lead in the atrial port and that was the electrocardiogram with His bundle pacing. We were able to overcome right bundle branch block because of this concept of proximal disease and committed fibers. So let me ask the audience a question. What is the average fiber length shortening of a healthy myocardial sarcomere? If you take a healthy myocyte and stimulate it maximally, remembering that our EF is 60%, how much do you think the fiber length shortens? The answer is 7%. That seems pretty miraculous, correct? How do you translate a 7% reduction in fiber length shortening into an ejection fraction of 60%? Almost wants to make you believe in a god. So how does nature translate a 7% shortening into an EF of 60%? It is driven by fiber orientation. It's the swirls and the whirls and by the perfectly timed delivery of electrical stimulus via the His-Purkinje system to perfectly coordinate the sequence of LV contraction. And left bundle branch block or right ventricular pacing or right-sided pre-excitation disrupts this coordinated sequence and therefore causes a drop in ejection fraction. So I think this is a great video to watch. This is a dissection that has been done off the heart and you can see, you can appreciate the swirls and whirls that go up, go on to make up left ventricular function and why you can achieve an ejection fraction of 60% when fiber length shortening is 7%. And there you have it. It's a complete swirl of contiguous fibers end-to-end that wrap around each other and that has to contract in the perfect sequence for you to get that ejection fraction of 60% and the left bundle branch achieves that. You have left bundle branch block, your ventricle is in trouble. So ladies and gentlemen, take-home messages. Number one, be on the lookout for tachymyopathy and dyssynchrony-mediated cardiomyopathy, especially AFib with heart failure, frequent PVCs, new left bundle branch block indicated by tall T-waves in the precordial leads and more than 20% right ventricular pacing. Medical therapy is at best an adjunct in tachymyopathy and it's seemingly futile in dyssynchrony cardiomyopathy so it behooves us to recommend ablation and CRT. Hallmark is correcting the offending factor either by ablation or resynchronization, resolves symptoms and it restores EF to normal and it's curable therefore. And few things in medicine are curable, right? We don't cure hypertension, diabetes, coronary disease, we manage them. But this is a cure for a certain proportion of patients provided you get them early enough before that irreversible slippage has occurred. The time course to cardiomyopathy development is variable and we are not yet fully understanding of that but we will be able to get to a better understanding in the near future I'm sure. Watch out for arrhythmia recurrence because some of these patients can have a rapid decline in LVEF when they redevelop the dyssynchrony or the tachycardia and that may be due to underlying ultrastructural abnormalities that remain even after you correct the problem. Why many patients seem to resist this dyssynchrony cardiomyopathy is unclear but maybe there is a role to mutations in the junctophile in gene that may make them more susceptible to that dyssynchrony because we've all seen patients with constant RV pacing or with long-standing left bundle branch block who show completely normal EFs but yet there are some people who take a crash quickly after development of RV pacing or left bundle branch block. Why the difference? There may be a genetic predisposition. The common theme is that the wider the QRS the greater the risk that's true for left bundle pacing and PVCs. When performing RV pacing in high grade AV block with anticipated more than 20% pacing please consider putting your lead on the mid septum or consider better yet his bundle pacing or left bundle area pacing to minimize the risk of developing dyssynchrony cardiomyopathy. The role of his bundle pacing is not yet fully defined but it makes sense that it is likely to be the ultimate form of CRT. We don't know about its long-term durability, extraction issues, etc. so those details have to be worked out. Several aspects of tachymyopathy remain unsolved. What are the predisposing factors? What are therapeutic strategies to prevent the ultrastructural changes and the long-term risk of sudden death? For patients with AF and heart failure you should consider offering ablation as virtually every study has reported improved EF after ablation. For patients with heart failure and sinus rates greater than 70 consider ivabredine based on the SHIFT trial to reduce at least heart failure hospitalization. Aim for more than 98% IV pacing in AF patients because less than 98% impacts adversely on mortality. For patients with frequent broad PVCs check the EF if it is abnormal offer them an ablation. All systematic reviews and meta-analyses have supported the use of ablation to improve ejection fraction in these patients. And for patients with more than 20% RV pacing check the ejection fraction and consider his bundle pacing or CRT before the EF reaches ICD territory as every study has reported improvement in EF after upgrade because these are truly correctable cardiomyopathies. And I thank you for your attention. That was fantastic. I don't think I've seen this data organized and summarized in that way. There were a few more questions. I'll try and ask them sequentially so they make some sense. A couple of them were related to diagnosing. So isolated left bundle cardiomyopathies and pacing induced cardiomyopathies. What do you do in terms of diagnostic testing? For the left bundle the question was in regard to you know inflammatory cardiomyopathies or sarcoid. Do you get a PET scan in everyone? And then for pacing induced if they had their pacemaker placed a long time ago do you go back to the beginning and rule out all other causes of cardiomyopathy before you settle on pacing induced cardiomyopathy? So I'll tell you that in clinical practice my personal threshold to recommend resynchronization is quite low. When I see a ventricle that is struggling in the setting of dyssynchrony my knee-jerk response is to immediately think will this patient benefit from CRT and I look for a reason to offer them CRT. But at the same time I have to try at least to look for reasons that identify a patient as being one who may not respond or at least has a high likelihood of response a lot lack of response to CRT. So I heavily depend on chronicity, atrial dimension, and MRI. The longer standing the cardiomyopathy has been the more the late gadolinium enhancement I find on MRI the less likely they are to respond. So if I see somebody with a end-stage heart you know left ventricle dilated to six centimeters you know awaiting heart transplant that's not the kind of patient I'm going to offer resynchronization to either for left bundle or for pacing induced cardiomyopathy. MRI with a large burden of late gadolinium enhancement I'm not going to offer them CRT. Very often these patients have pre-existing leads that may be abandoned, vascular access can be a problem, occluded vessels. Those are patients that again I think twice before recommending upgrade in any way because it often involves doing an extraction to access the heart which is pretty high risk. In terms of excluding other cardiomyopathies like sarcoid, yes that is very important. If you have any suspicion that this is sarcoid then you really are required to exclude that. So chest x-ray, pulmonary findings, hyaluronidinopathy, blood testing, all of these are appropriate to consider if your clinical index of suspicion is even modest for sarcoidosis because as you know in those patients immunotherapy will often improve ejection fraction. Immunotherapy has been proven to reduce PVC burden and reverse the cardiomyopathy and you don't even need to do an ablation in those patients. So yes if you have any suspicion for an infiltrative process you should offer them a workup for that and treatment if you find it. Amyloidosis unfortunately patients don't do well no matter what you do. So again for that indication I often think hard before offering them CRT because those ventricles are basically not going to respond whether you resynchronize them or not. Then one of the other questions was in patients who have multifocal PVCs what do you do in terms of offering them ablation versus drugs or what drives you one direction or the other? Correct. So again a tough clinical scenario. I often look at the Holter result and at least some Holters especially the older generations now we don't see that with the patch Holters anymore but with the older generation Holters they used to actually quantify the PVC morphologies. Some of the modern ones still do that as well. So if you look at multiple morphologies of PVCs but if you look at the distribution if you find that 80% of the PVCs are coming from one morphology and the other four PVCs make up 20% then that's a kind of patient where you might want to think about offering them an ablation. But really if there are four morphologies that look completely bizarre and not you know a predictable location and they are sort of equally distributed among the four different morphologies then I would not offer them ablation. I would think about trying medical therapy first. I tell you that I have done ablations for patients who show two morphologies of equal distribution provided I'm convinced that they are coming from you know recognizable locations like RVOT and left posterior fascicle. Sure I'll ablate both of those if the PVC burden is high and the ventricle is failing I believe I can get those two with a reasonable degree of success. But if the morphology is not consistent with any predictable location it looks epicardial it looks very bizarre and wide and there are multiple morphologies then I will think about medical therapy first. So it's a clinical judgment call depends on how comfortable you are with your procedure how much imaging support you have and so on. It's an individual judgment you make for a patient. Again Nishant and Rod and anybody else please jump in if you have additional thoughts and recommendations. I think I would agree with what you said there and then one other question was the role of left bundle branch pacing versus his pacing. Do you think one is better than the other? Okay that's a probably a different topic from what we are covering today but I'm happy to share some thoughts that I have and some of the preliminary data. There are pros and cons to each strategy. What are the pros of his bundle pacing? You have a very nice narrow QRS complex. There is no even if there is some non selective capture and you're pacing part of the ventricular septum you're still going to achieve perfect resynchronization because timing of the free wall occurs through the left bundle branches and it's like having a delta wave in the septum. It's like having a septal pathway and those patients do quite well. There is no lead that crosses the tricuspid valve so there's no tricuspid regurgitation involved and the procedure has been around a little bit longer than left bundle branch area pacing. The disadvantage of his bundle pacing is that you have a problem with thresholds over time. In a substantial number of patients the thresholds may creep up. The sensed R waves are small because you're in the membranous portion of the septum. You might pick up atrial signals from that location and lead to false inhibition. Programming sensitivity and outputs and battery life are all issues. For left bundle area pacing the benefits are that you have always have myocardial captures. You never have to worry about losing capture if you have complete heart block and pacemaker dependency. It's a little bit of a hit and miss at least in my own personal experience which is small I will admit freely that I have encountered patients where I burrow through the septum towards the left endocardium and I find that left bundle signal and I pace from there I get a right bundle morphology QRS duration drops down to like 110 120 and I'm thrilled but then I have patients where I have burrowed three times I can't seem to find anything that looks like a left bundle and then I finally land up just leaving it in the myocardium of the septum but even there I have to admit the QRS duration is not terribly wide. It is quite narrow. It's usually in the 120 to 130 range. It's certainly better than RV endocardial or RV apical pacing for sure. So my sequence is that I usually give his bundle pacing a good try but I don't try his bundle pacing in patients who may have intra his block. Then I go on to left bundle area pacing and if that results in a QRS duration that is less than 130 I accept it. If not I do what is called hot CRT where I also put in an LV lead and pace the septum and the LV free wall and that can often result in really dramatic narrowing of the QRS complex.
Video Summary
The video transcript discusses two types of cardiomyopathies: tachymyopathy and dyssynchrony-mediated cardiomyopathy. Tachymyopathy is caused by rapid heart rates, such as atrial fibrillation, while dyssynchrony-mediated cardiomyopathy is caused by disruptions in the coordinated contraction of the left ventricle. The speaker emphasizes the importance of identifying and treating these cardiomyopathies early, as they are reversible conditions. Medical therapy alone is not very effective, so the speaker recommends ablation or cardiac resynchronization therapy (CRT) as treatment options. Other causes of cardiomyopathy mentioned include frequent premature ventricular contractions (PVCs) and pacing-induced cardiomyopathy. For patients with frequent PVCs, the speaker recommends checking ejection fraction (EF) and considering ablation if it is abnormal. For pacing-induced cardiomyopathy, upgrading to CRT is recommended before EF reaches critical levels. The speaker also mentions a potential treatment option called his bundle pacing for dyssynchrony-mediated cardiomyopathy, involving stimulating the bundle of His. However, more research is needed to fully understand its effectiveness. Overall, the speaker emphasizes the importance of timely intervention and selecting the most appropriate treatment option for each patient.
Keywords
cardiomyopathies
tachymyopathy
dyssynchrony-mediated cardiomyopathy
rapid heart rates
atrial fibrillation
ablation
cardiac resynchronization therapy
premature ventricular contractions
PVCs
ejection fraction
his bundle pacing
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