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EP Fellows Curriculum: Hypertrophic Cardiomyopathy ...
EP Fellows Curriculum: Hypertrophic Cardiomyopathy ...
EP Fellows Curriculum: Hypertrophic Cardiomyopathy - Diagnosis and Treatment 2020
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And thanks for not only inviting me, but for doing this whole series, which I think is a wonderful series. And all of our fellows here spend their Saturday watching it. They're not watching it on Friday morning live anymore, but they are all watching it on Saturday. So I'm pleased to give you the talk on hypertrophic cardiomyopathy today. It's been a passion of mine for over 20 years. You know, I started the HCM Center at Tufts prior to Marty Maren coming. And I've been a big participant in the HCM Center down here, which was started by Aslan Turar. So I'm gonna have a little background first. The significance of HCM is it's the most common cardiovascular genetic disease. It's the most common cause of sudden death in the young and in athletes. But it affects individuals of any age. It's unrecognized clinically in many patients. And it's an important cause of cardiovascular disability, including heart failure, AFib, and stroke. And it's something that we as EPs will certainly be seeing these patients because they have AFib and they have sudden cardiac death. This is a typical MRI that you can see the markedly thickened septum. It's important, it's defined by unexplained ALB hypertrophy, and that's important, unexplained. So there's nothing else that could cause the hypertrophy. But it's important to recognize there is a differential diagnosis of HCM. So don't always assume what you're seeing is HCM. Athlete's heart is one that pretty commonly referred to us to try to determine whether it's athlete's heart or HCM. With MRI, it's becoming a little bit easier to tell the difference, but still is a diagnostic dilemma in many people. The infiltrated storage diseases can look like HCM. Mitochondrial disease can look like a Fabry's. We always find a Fabry's every few years that's been diagnosed as HCM for years. A Noonan syndrome, hypertensive heart disease, especially in the more elderly population, sarcoid, amyloid, and non-compaction. So always think that these diseases could be present also. Just a little bit about the treatment of the heart failure symptoms, and I'm gonna focus really on REP involvement here. If they're not obstructive, it's medicines. It's all you have, medicines and then transplants. If it's obstructive, you have the medicines, but in addition, you have surgical myectomies and alcohol septal ablation. Now, determining who should get a surgical myectomy and who should get an alcohol septal ablation is really gonna be dependent on the center that you're at, because some centers just don't do septal myectomies. Alcohol septal ablation is done, you find a septal perforator that feeds the area of the septum that obstructs. And so whether it's gonna be the first or the second really depends on the individual anatomy. So you're gonna find that septal perforator, you go in with a balloon, occlude the vessel, and then inject one to three cc's of ethanol. More and more now we're injecting less, and we're going down to one cc. Some of you may recall there was an ablation paper that you could do radiofrequency ablation for this, came out of Europe somewhere, I forget exactly where. But if you look at that paper, their mortality rate was like 15 to 20%, so an incredible mortality rate. So not something I would advise at this point. And then surgical myectomy goes through the aorta and basically creates a trough in the septum. Now, why do we have to know this? And here's again, how you sort of pick. If you have a good surgeon that does septal myectomies, and you have a younger age group that's otherwise reasonably healthy or needs other cardiac surgery, septal myectomy is the choice. The older people get, the more unfavorable surgical candidates they are, the more alcohol septal ablation should be done. But what's important is that in the US, there's becoming a shortage of myectomy surgeons. And so there are many centers that don't have a good myectomy surgeon anymore. And if you don't have a good myectomy surgeon, you shouldn't be doing myectomies. Now, why is this important to us? It's because pacemakers are pretty common after both myectomy and after alcohol septal ablation. The Mayo series would say that the myectomy heart block is three to 5%. There's no other series that's that low. Almost every other series is gonna say 10% after myectomies. And alcohol septal ablation is probably a little bit higher risk of heart block than myectomies. Now, importantly, if you look at alcohol septal ablation pre-op normal conduction, 40% get a right bundle branch block after alcohol septal ablation, 40%. So that means if you start with a left bundle and you have a 40% chance of getting a right bundle, you're gonna get complete heart block. And in this series, 75% of those that had a preexisting left bundle got complete heart block. And so you can tell your patients before they go in, what are their odds? And myectomy is exactly the opposite. In myectomies, you create a left bundle in roughly 50%. So if you start with a right bundle and you add a left bundle, you're gonna get complete heart block. So this might play some role in the choice of procedure also. And this is the way I remembered is surgical myectomy goes in through the left. You're taking the left side of the septum out. So that's where the left bundle is. And alcohol septal ablation is just the opposite. I honestly don't know why alcohol septal ablation preferentially affects the right bundle, but it does in every series. A right bundle branch block is very common after alcohol septal ablation. This is a paper that's just published that is actually not even published in print yet, but it is on the web. And it's a series of patients that got alcohol septal ablation and then got implantable monitors placed. And you can see that the incidence of heart block now in this long-term population approaches 20%. And the early heart block is that previous slide is probably 10 to 15%, but even later you get heart block in these patients. So alcohol septal ablation has a relatively high incidence of needing pacemakers afterwards. And then if you're gonna need a pacemaker, you have to look pretty hard to see if there's any indication to give them an ICD. And we'll get into that when we go into our ICD section. Okay, that's heart block. Heart block is predominantly only seen in patients that have undergone procedures. Incidence of heart block in other individuals is no higher than the normal population. AFib, however, is very common in patients with HCM. And here's the age-related prevalence. In the young, it's unusual, but a 7% incidence of AFib in individuals under 30 is very high compared to normals. Normals, it's nowhere near that. But the incidence increases with age. And when you start to get out here in the over 60s, you're starting to talk about 40% incidence of AFib. And when you get AFib, it's associated, not necessarily causal, because it may mean your disease is worse, but it's clearly associated with a worse outcome. And if you look at survival patterns here, the survival over a 10-year follow-up, 25% of people die that have AFib. And chronic AFib, no surprise, is worse than paroxysmal AFib, because chronic AFib is further down the road. And then younger age, it's actually worse to get AFib at a younger age. And again, this is an association and may solely reflect the fact that if you're getting AFib, you have a worse phenotype. We know that AFib in HCM, just as it does in non-ACM, increases heart failure admissions dramatically. And in this series that's from Japan, the heart failure admissions were over 90% in patients with AFib. And in patients without AFib, it was 20%. And AFib, no surprise, increases embolic events. Again, in this series from Japan, number of embolic events was very, very high. It's interesting that the prognostic impact of AFib in hypertrophic cardiomyopathy is much worse than AFib in the general population or AFib in heart failure. The cardiovascular death is four-fold higher in HCM when you have AFib, compared to 1.5 to 1.9 higher when it's in the general population, and 1.4 higher in the heart failure population. And the risk of stroke, and the risk of stroke, look at the risk of stroke here, eight-fold higher than those without AFib, whereas in the general population, it's only four-fold higher. The predictors of AFib are age at diagnosis greater than 50, heart failure, class II, and then even worse with class III or IV, and then the left atrial dimension greater than 45 milliliters. So those are the four risk factors. So let's move now to the treatment of AFib. We're first gonna talk about anticoagulation. I showed you the slides before, and I could show you multiple other series that show you that HCM patients with AFib are at very high risk of thromboembolism, and this is important. You do not use the CHADS-2 and the CHADS-VASc scoring systems. They don't apply to HCM, because in HCM, the yearly risk of stroke is around four when you have AFib, so you are equivalent to a CHADS-VASc of four. So it doesn't make any difference if your CHADS-VASc is zero. If you're an HCM patient, you're at least at 4% risk of stroke per year, and so again, I see this time and time again. People apply the CHADS-VASc score to HCM patients. That should never be done, and so in general, we should be more aggressive in anticoagulation in HCM patients compared to non-HCM patients. The time length of AFib is always an issue, and I know that Dr. Passman has published a very nice paper on this in CERC in the combination of time in AFib, density in AFib, and CHADS-VASc. We don't have that kind of data in HCM, so it's extrapolation from the other series in non-HCM, but what I generally say is if it's a 24-hour episode of AFib, that is long enough that they should be anticoagulated. If it's less than a five-minute episode, which we frequently will see on devices, then in general, I think you can avoid anticoagulation, and if it's between five minutes and 24 hours, that's a gray zone, and as in many gray zones, you weigh the risk and benefits of anticoagulation. The longer the episodes, the more frequent the episodes, the more they should get anticoagulation. The shorter the episodes, if you have 10 minutes and it occurs once in six months, I'd be pretty comfortable not anticoagulating that. However, if you've got 12-hour episodes and they're occurring three times a week, that kind of patient, I would want to anticoagulate. So again, that gray zone is between six minutes, five minutes, and 24 hours, and that's true of all patients. That's true not only in the HCM population. That's true in the regular population also, and this is the paper that Rod published that if you had a higher CHA2DS2-VASc score, you didn't need as much Afib in order to put you at risk of stroke. You can use the vitamin K antagonist or the direct anticoagulants. There was some pushback originally in 2011 that there wasn't data on the direct anticoagulants, but I would argue there's a lack of data also on warfarin, and it's become widely accepted now that you can use the direct anticoagulants or warfarin just as you can in other diseases. So that's anticoagulation. I tend to use very little warfarin in my practice anymore just because it's so painful to use, but I don't think there's anything wrong with warfarin. I think it's a perfectly reasonable drug for people that can tolerate it and can tolerate the INRs. Rate control in Afib is often difficult, and it's difficult because they tend to be younger patients, and so their AV nodes are more functional than the AV nodes of 80-year-olds, but you use the same agents with Afib. You use beta-Agnes, non-dihydroprene, calcium channel blockers, and you often need a combination of both of those, and then when you do that, you'll get notified by the pharmacist that don't you know that this may cause bradycardia? Yes, that's why we're using it, so you'll frequently get those calls from the pharmacist, but you will often need both. I've found that most of my younger HCM patients do not like being in Afib. They just don't go for a rate control strategy because they're miserable. The older a person gets, I find the better tolerated Afib is, and I'm not exactly sure why that is, but I think that's probably true in non-HCM populations also, and this is the agents we have for pharmacologic control in HCM. We have the class 1A disoperamide and then the class 3s. Just like in other types of heart disease, I don't use the 1Cs, even though there really isn't any data specific to hypertrophic cardiomyopathy that these agents are dangerous, just like there's very little data in diseases other than coronary disease. This is all extrapolation from CAS, which is coronary disease. Then there's catheter-based ablation. We'll spend a little time on that in incertical maze. The data for disoperamide treatment of Afib is really kind of weak. What this slide shows is that at least it does not increase sudden cardiac death. This is a treatment of heart failure symptoms, not a treatment of Afib, and it shows that the disoperamide treatment did not at least increase the risk of sudden cardiac death. So in the 2011 guidelines, disoperamide gets a 2A. It is reasonable as an antiarrhythmic drug. Amiodarone, again, surprisingly little data on these antiarrhythmic drugs and HCM patients, but this is an old paper, 1990, in which amiodarone was used. And again, there was no sign of toxicity here, but relatively short-term. This is probably a two- or three-year follow-up, but did maintain sinus rhythm in most patients. The story in the Oliveto series is not the same. Oliveto series is the largest series of Afib in hypertrophic cardiomyopathy that's been published. And of the 77 with PAF, 43 were treated with amiodarone, but there was no difference of sinus rhythm and survival, even when you corrected for heart association class, left atrial size, and Afib development. Amiodarone still gets a 2A indication because it's thought at least to be safe in hypertrophic cardiomyopathy. So while you can tell how old this slide is by the quality of the figure, 30 patients with HCM, double-blind crossover, and it was used for both SVT and VT in this group. And it eliminated SVT, which was largely Afib, in six of seven patients. We published our data from Tufts last year, and we defined efficacy as really staying on the drug. That was our primarily way we defined efficacy because no one expects them on drug treatment to have no episodes. And importantly, I tell my patients that, is that you are going to have episodes. This is not going to completely cure you of Afib. And we used predominantly four drugs, amiodarone, disoperamide, dofetilide, and sodalol. And you can see that they're all roughly similar. There was no difference. There was no significant difference between these drugs. And roughly at the end of three years, 50% of the individuals stayed on that drug. So, again, not great, not perfect, but not horrible. I mean, we're still getting control. And that included all four of these drugs were very similar, right? You know, three years, about 50% of people still stayed on the drug. Now, they were having episodes, to be sure, but the physician and the patient thought the drugs were good enough to continue. Importantly, this safety signal, when you look in here, it's not horrible. There was non-sustained BT in four individuals on sodalol. Non-sustained BT, no one had sustained BT. Shortness of breath was in one that caused discontinuation. Amiodarone had no safety events, but a lot of side effects causing discontinuation. Disoperamide surprisingly had a high number of safety effects, including anaphylaxis, non-sustained BT, and sustained BT and QT prolongation. And then, not surprisingly, a high amount of anticholinergic side effects causing discontinuation. And then dofetilide had some non-sustained BT, symptomatic bradycardia, which I know it's not supposed to cause, but one patient had it discontinued for that, and two patients with syncope, which was really concerning and had it discontinued. And almost 15% quit for side effects causing discontinuation. So probably similar, I don't think any different to what you would see in other populations. These are potent drugs that have real issues with them. And so, estonal dofetilide and dronetarone are given to be indications for patients with HCM. What about ablation? There's increasing data about ablation. In fact, there's more data about ablation with HCM than there is about antiarrhythmic drugs. This is one of the early series that has been published, and basically, most other series are gonna show you the same thing. When you take people with HCM and ablate them, you don't have as a high success rate as you do with non-HCM. So there is something about HCM that lowers the success of ablation. And when you look at what that is, there are a couple things that are important. Left atrial size is probably the biggest importance. And again, this is true in non-HCM. Once the left atrium dilates, it's a marker for an atrial myopathy. It's a marker for increased left atrial pressure. So it isn't necessarily causal as much as a marker, but it is clearly a marker. And so I try, if we're gonna go for a rhythm control strategy in HCM patients, I try to move earlier to ablation and try to prevent this left atrial dilatation. Again, there's no proof on preventing the left atrial dilatation, but I don't like to wait until they get big dilated left atrium. I think that's a mistake. Radiofrequency ablation is given a two-way indication in the 2011 guidelines. Now, the guidelines are being rewritten and will come out either later this year or early in 2021. And then this is the flow chart from that guideline. Now we're gonna shift to ventricular arrhythmias and sudden cardiac death in HCM. Barry Marin's published a lot on this. When you look at Barry Marin's series, HCM is always the number one cause of sudden cardiac death in his series. Now, importantly, that's not true in all series. That's not true in data that comes out of New Zealand or Australia, but HCM is a common cause of sudden cardiac death in the young. There's an age-dependent mortality in HCM. The younger you are, the more likely you are to die suddenly. And as you age, the sudden death risk drops a little bit and the risk of dying of stroke and heart failure increases. A little bit of this is survival of the fittest. If you have a very poor phenotype, then you're more likely to die when you're young. And when you die when you're young, you're not gonna live to have stroke and heart failure. These are the traditional risk factors for sudden cardiac death. Again, if you've had prior sudden cardiac death that you've been resuscitated, of course, you're at high risk and that makes it easy. These are the five other traditional risk factors. Family, and we'll go into these, family history of sudden death, massive hypertrophy, syncope, non-sustainability, hypotensive response to exercise. Again, the guidelines are being rewritten and this is being looked at. So this is a slide from one of Barry Marin's series that looks at the ICD shocks or ICD treated arrhythmias in primary prevention versus secondary prevention. And you can see the secondary prevention, Kaplan-Meier curve is very steep. And at two years, 25% have had some intervention. And by five years, about 35, 40% have had some intervention. So very high rate of ICD therapy in people that have had a prior sudden cardiac death. Again, no surprise. This curve is also relatively steep for a primary prevention group and reflects really the clinical diagnostic acumen of picking the patients that are more at risk. Now, I fully recognize that ICD shocks are not a surrogate for sudden cardiac death. And everyone recognizes that. And these are ICD shocks. Wall thickness has come out as one of the leading risk factors. And you can see that it's a continuum. It's not an abrupt step up of 30. We use 30 in the current guidelines, but the Europeans, I think, do it more correctly, and they use this as a continuous variable. Where does this 30 come from? This comes from a Barry Marin series that you can see individuals that have 30 millimeters of thickness, and that's anywhere in their heart, have the highest likelihood of sudden cardiac death. This is a slide from Elliott that actually came out after the Barry Marin series and confirmed what he had found. In nearly all series, a family medical history of sudden cardiac death is one of the strongest predictors, and it's kind of interesting that, by implication, you would think that genetic analysis would be a stronger predictor of sudden cardiac death, but not as strong as we would have thought. And the reason it is is because there are only a dozen or so genes involved in the abnormalities, but within those genes, there are hundreds, if not thousands, of mutations that can cause problems. And so different mutations in the same gene are not going to cause the same risk of sudden cardiac death. I don't have the slide in here, but there was a series from the SHARE Registry that I should update here. And what they found in the SHARE Registry is the individuals who had a gene abnormality, a positive mutation for HCM, were more likely to have an ICD shock or sudden cardiac death than those without a gene. They could not find any specific gene that caused them to be at higher risk, but just having a genetic abnormality puts you at higher risk. Syncope, if it's unexplained, that is, if it sounds arrhythmic, and it's relatively recent in onset, does predict for sudden cardiac death. Syncope that occurs in childhood, syncope that's vasovagal, does not predict for sudden cardiac death. So this has to be unexplained syncope that occurs in individuals. Non-sustained PT is very important. It's not just having non-sustained PT. There's a couple of things about the non-sustained PT. Importantly, the age at non-sustained PT is very important. And if the age is under 30, it's very predictive of sudden cardiac death. And this is a problem because you'll have an adolescent come in with non-sustained PT, and I'm much more concerned about that adolescent than I would be if the individual came to me at age 55. And in this series, age greater than 30 did not predict for sudden cardiac death. And this has been shown in a couple other series too, that age, especially as you start to approach 60, non-sustained PT doesn't make any difference. But it's not only the age, it's the rate. And again, this is something you would expect, but never had been shown until 2017 that the individuals with faster non-sustained PT, and in this study, the cutoff was 200, but you could look at it at 180. It was really more of a continuous variable. The faster the rate, the more concerning the non-sustained PT. And again, not surprising, but not shown until this study in 2017, is the length also played a role. The longer episodes of non-sustained PT were more concerning than the shorter episodes. Multiple risk factors puts you at higher risk. Study from Perry Elliott in Great Britain. Now there's some emerging risk factors in HCM, and these are being looked at very closely in the upcoming guidelines. Probably the one with the greatest data currently is the gadolinium enhancement, or we call it fibrosis, but it's really gadolinium enhancement on the MRI. This is an example of gadolinium enhancement. You can see these white areas, and we all know, we're getting quite familiar with gadolinium enhancement, not only in HCM, but in the non ischemic cardiomyopathies and in scar-related PT ablation. So as EP, we are getting to be more expert in the MRI. And this is a study from Boston, from the BI and Tufts, that when you quantify a scar, the more scar you have, the more risk of sudden cardiac death events. And the cutoff here is somewhere between 15 and 20%. Now I would caution you that the gain settings on the MRI make a huge difference to scar. So you have to be familiar with what your institution calls scar and not. And so I'm a little troubled by this because I've had patients sent to me with 50 to 55% scar burden. That's impossible. You can't have 55% scar burden and live. And these patients were without heart failure. So again, I'm a little concerned about the fidelity of this across the institutions. Alphalete tract reconstruction makes a little difference, not a big difference. Apical aneurysms probably makes a big difference. And it's important that this is apical aneurysms. This is not apical HCM. There's a huge difference between the two. Apical aneurysms occur more in a late stage of HCM and are scar. And as scar in other conditions, scar predisposes to ventricular arrhythmias. And interestingly, the ventricular arrhythmias in apical aneurysms tend to be more monomorphic VT. And the ventricular arrhythmias in garden variety HCM tend to be more ventricular fibrillation. So these are very ablatable arrhythmias. And this starts from Tufts. If you have an apical aneurysm, your risk of having VT or VF is markedly higher than if you don't. In-stage disease. And in-stage disease in HCM is really defined as an EF less than 50%. Because patients with HCM start with EFs greater than 70%. So to see an EF of 45% in an HCM patient is a dramatic drop in their left ventricular ejection fraction. This is from 2011. This will be updated, but 2011, this is what we walked through. Prior cardiac arrest, yes, you should get an ICD. These are the three major risk factors in 2011. Family history, alveolar thickness, recent unexplained syncope, ICD is reasonable. And then non-sustained VT or abnormal blood pressure response were thought to be less of risk factors. Now, I would argue if the non-sustained VT is fast or long, or they're young, I would argue that that's a much more important risk factor than if it's short and slow. But in this group, you can look for other sudden cardiac death modifiers. And those include the ones we just talked about. Alveolar obstructive obstruction, LGE, apical aneurysms, or multiple genetic abnormalities. So if you have any of those, you should, well, the ICD can be useful. ESC has a calculator and the differences are that they use age and alveolar thickness as continuous variables, not as binary. They still use the family history, non-sustained VT and syncope as binary. They add left atrial size as a continuous variable. And left atrial size is a marker of disease. It's a marker of badness. They also use alveolar tract gradient as a continuous variable. They use this equation, which no one can use, but luckily they provide a calculator. And if you Google ESC HCM calculator, you'll come to the page that gives you this. And then when you click on it, you can just plug in the variables. And what the ESC calculator will do will give you a five-year risk of a sudden cardiac death. And they split it up into risk less than 4% at five years, less than 4% at five years, four to 6% at five years, greater than 6% at five years. So that's what they use. And in their document, what they say is that if it's greater than 6%, you probably should get an ICD. But if it's less than 6%, you probably shouldn't get an ICD. So there is a difference in thinking between the United States and across the pond in who should get ICDs. And there's no doubt more patients would get ICDs in the US system than in the ESC system. This is a validation. And in their validation cohort, you can see that, yeah, the high-risk individuals had a fair amount of sudden cardiac death, but the low-risk ones didn't have a terribly low risk. And there was no difference between the low-risk less than 4% and the four to 6%. And when you look at that series, the low-risk and intermediate risk accounted for 86% of the cohort, but over half of the deaths. So over half the deaths in that population were defined as low-risk. And that's a problem. And it's a problem with HCM is that we don't have a great risk tool. And I'm the first to admit that the US is not fantastic either. These are based on limited number of patients. It's a heterogeneous disease. It's not so easy to predict the future in hypertrophic cardiomyopathy. So the first decision is who should get an ICD. And then the second decision is, should they get a transvenous versus a subcutaneous ICD? So the first decision was what we've just talked about for the last five, 10 minutes, are the risk factor analysis. But now that you've decided that an ICD is necessary or is wanted, I should say, there's other things that go into that decision, including patient's age. Do they have kids that depend on them? Other comorbidities. It's a shared decision-making. It really is on who should get ICDs. But now that you're gonna get one, let's look at the data for transvenous versus subcutaneous. So a couple of trials. I'm gonna go over those. So we all know the benefits of transvenous ICDs. There's a long track record. They can pace both ATP, sinus gradient, CRT, and they have long battery lives. The current transvenous ICDs are 10 to 14 years. We all know the risks. Lead failure. They all do have inappropriate shocks. Endocarditis or infection is a real issue. And then extracting them is not so easy and has real risks. This is the Fidelis fiasco. When the Fidelis lead came out, it was a great lead. It was thinner. It was easy to implant. I loved the Fidelis lead when it came out. But look at what happened over time. It just disintegrated. And it fell apart for a couple of reasons. One was that the tip was soldered. And so there was a lot of breaks there, which is an unusual place to break at the coil. And then it also wore out in the insulation at the shoulder and that's a more common place where leads fail. This is data from CHOPS that again, shows the monomorphic VT accounts for about half the episodes. And the reason this can be important is that ATP can terminate monomorphic VT, whereas it's likely not gonna terminate VF. Importantly, most of the monomorphic VT episodes were in people with apical aneurysms. So for people with apical aneurysms, there is a potential benefit to getting a transvenous device so you can get ATP. And the success of ATP is very high, even for these very fast flutters. Now here's the device implantation related complications over 12 months for transvenous ICDs, not small. Hematoma, 5%, lead dislodgement, 2%. And if it's a dual chamber, it's even higher. Pacing threshold elevation, corrosions. And so a 9% one year incidence of device complications. That's in a non HCM population, but it's high. It's higher than we would like. And then what about recalls? This is the Fidelis lead picture I showed you before, but this is an even more concerning Fidelis lead picture. When you look at individuals who are younger than 20, their Fidelis lead fell apart. And at five years, there was a 40% failure rate of the Fidelis lead. So an incredibly high failure rate in individuals under 20, and very important for our HCM population because there's a fair number of patients under age 40. And the other thing I feel strongly about is you really have to think about, if you're gonna put a transvenous device in these young individuals, you have to really think about an atrial lead. Because an atrial lead increases the both short-term risk of complications and long-term risk of complications. And so I'm a big fan of simplicity that I think in general, the default should be a single chamber. The default should be a single chamber ICD for individuals with HCM. Because again, they rarely develop heart block and therefore rarely need. Brings us to the subcutaneous ICD. And I know Northwestern is a big fan of these, so I don't have to sing its praises. The big advantages are no transvenous leads, so you don't have subject to wear and tear. It doesn't rub over the can. It's easy to put in, it's easy to take out. Disadvantages is it's a bigger can, it can't ATP. There's some T-wave over-sensing and fascicular over-sensing. And there's concern about defibrillation efficacy, especially in patients with HCM. Now, fellows don't even see this anymore because it's an automatic tool that checks for T-wave over-sensing. But this is the theory and this is what we used to do before we had the automatic algorithm. You'd print out strips and it would be the same strips that, vector one, vector two, vector three. Then you'd use this very colorful tool to see and then find out where the R-wave, you'd put the R-wave in this location and then make sure that the T-wave fell within the colored zone. And this is an appropriate one. The T-wave is all within the colored zone. And this is an inappropriate one because the colored wave got out. Nowadays, you won't see this tool anymore, but this is what the automatic algorithm is doing. This is from the IDE trial. And that, you can see there's a lot of inappropriate shocks. The IDE trial included patients without HCM. So in the early trials of subcutaneous ICDs, there was a lot of inappropriate shocks. And that's been dropped quite a bit by a number of technological enhancements. The first one, including a dual rate zone, which dropped it a lot. And then the other thing that happened is they're sensing algorithm change. And in series of subcutaneous ICDs, HCM does have a higher risk of inappropriate shock. So it is there. And this is the SmartPASS algorithm. And with the SmartPASS algorithm, the data is that the inappropriate shock rate is probably similar to transvenous ICDs. Importantly, I think is programming for subcutaneous ICDs and actually transvenous ICDs in patients that have hypertrophic cardiomyopathy. More often, these are younger compared to our patients with coronary disease that are getting devices. And in a younger population, you really have to set the VT and VF zone at a much higher rate. So I set my VT zones typically somewhere between 200 to 220 on my patient with HCM. The age, if you think of an individual's 16 years old, then their maximum heart rate on average is gonna be 204 beats a minute. And that's the average. So there's a wide standard deviation around that. So for someone aged 16, they should not be programmed for a VT zone at 200 beats a minute. Their VT zone should be at least 220 and their VF zone, 250. And I think that's, I see this quite commonly that these young individuals are set with zones typical to our CAD patients, and that's a mistake. A 16 year old should never be set with a VT zone at 180 beats a minute. So that's important when you take care of these patients is to think of the programming also. So in conclusion, AFib and stroke are very important aspects of HCM. AFib is more concerning in HCM than in other populations and thus should be anticoagulated at an earlier stage. Treatment for AFib is similar to treatment for AFib in other conditions. That includes antiarrhythmic drugs and ablation, but treatment is more difficult in HCM. Success rates for both drugs and for ablation are lower in HCM than in other cohorts. HCM patients have a risk of dying suddenly and every HCM patient has some increased risk. There's no HCM patient that I think has no risk. The problem is we incompletely have the ability to predict which ones are going to die suddenly. And so there's no doubt that we put in too many ICDs. It's just that we don't know which ones not to put ICDs in. The European calculator has a higher specificity, but a lower sensitivity than the U.S. calculator. And the ICDs save lives and I'm a big fan of ICDs, but not without risk of their own. So again, thank you for having me. Thank you, Nishan, for doing this series. I think this series is fantastic. Our fellows have truly enjoyed this and learned so much about EP. And I think it's a great idea that it's living on YouTube that everyone can go back and look at these presentations. Thank you. That was a fantastic review. There are a few questions, if you don't mind answering. Maybe I'll start with the ones that seem related to risk stratification. Does apical HCM have the same ventricular arrhythmia risk as other forms of HCM? Yeah, the apical HCM, and again, different than apical aneurysms, and this is the so-called Yamaguchi variety because it was first described in Japan, probably has less of a risk. And part of that may be that these individuals don't tend to have as thick a septum or as thick of hypertrophy as the non-apical patients. So probably lower risk. The data would support that. And then you already touched on this, but I'll ask it. NSVT is a risk factor. I think all of us have seen a 60-year-old with a triplet get implanted with an ICD. How much NSVT do you really worry about and do you use other criteria? Yeah, I definitely use other criteria. NSVT is not all the same. The younger the individual, the more concerned I am about NSVT. The longer it is and the faster it is, the more I'm concerned. We published data from the Tuft Registry that once you hit age 60, probably none of the risk factors make any difference anymore because you've survived. So I would agree with you that a three-beat run of non-SVT in a 60-year-old with HCM wouldn't bother me and wouldn't make me, wouldn't want me to put an ICD in. But an eight-beat episode of non-SVT in a 16-year-old and that's 200 beats a minute, that really bothers me. I know it's hard to put in devices in kids, but that would really bother me. And then in terms of devices, is there any role for pacing for LVOT obstruction nowadays? Or is that not a consideration anymore? Yeah, I actually thought about including those slides because I still think there's a role in certain patients. If you look at the randomized data, randomized data would say overall the population doesn't benefit, but there appears to be a subset that does benefit. And that subset is the individuals over age 60. So there are times when I will put a pacemaker or defibrillator in individuals over 60 who are having real heart failure symptoms and have obstruction. Importantly, you have to have obstruction. There's a role still, but that is not a role for people under age 60. I do not think the data warrant younger individuals getting heart beat pacing. But yes, over 60, alpha tract obstruction, symptoms of heart failure. Yes, I think there's a role. Okay, and then there's a couple of AFib questions. One is whether you think the AFib from these HCM patients are due to the genetic mutation or is it ventricular dysfunction or hypertrophy that predisposes them to AFib with left atrial enlargement? Yeah, interesting question, good question. There's clear evidence of an atrial myopathy in HCM. So there's no doubt that's the genetic abnormality that has an atrial myopathy. There's also clear evidence that the higher the left atrial pressure and the more left atrial stretch you get, which are related, of course, the higher risk of AFib. And that's the left ventricular side. So there's both aspects. And I think that's why AFib is more common in HCM than it is in other forms of heart disease. And then the second question is about ablation for AFib. I think most of us get the sense that maybe PVI alone won't control AFib, but do you have some guidance in terms of lesion sets that you would recommend? Yeah, I treat my HCM patients with AFib in terms of ablation with the same strategy I treat my non-HCM patients, to be honest. So my strategy, and again, I'm not saying this is the only strategy, but it's my strategies. I like to do a cryo balloon first, and sometimes I'll do a roof line with the cryo balloon, especially if there's a short roof line to do. But I tend to stop there. So I tend to do just PVIs on the initial ablation, but then for repeats, then I would go in with a radio frequency. I would touch up the veins. I would do a roof line. I would do a floor line. I'd isolate the posterior wall. Consider doing a cable tricuspidismus line. But I really do treat them the same in terms of ablation strategy as I treat my other AFib patients.
Video Summary
In this video summary, Dr. Barry Maron discusses hypertrophic cardiomyopathy (HCM), the most common cardiovascular genetic disease. HCM is the most common cause of sudden death in young individuals and athletes, but it can affect individuals of any age. It is often unrecognized and can lead to heart failure, atrial fibrillation (AFib), and stroke. Diagnosis is typically made based on unexplained ALB hypertrophy and ruling out other differential diagnoses. Treatment options for heart failure symptoms include medications, transplants, surgical myectomies, and alcohol septal ablation. The choice between surgical myectomy and alcohol septal ablation depends on individual anatomy and the availability of experienced surgeons. AFib is common in individuals with HCM and is associated with a worse outcome. Anticoagulation is essential for HCM patients with AFib due to the higher risk of stroke. Risk stratification for sudden cardiac death in HCM is complex and based on several factors including family history, alveolar thickness, recent unexplained syncope, and non-sustained ventricular tachycardia (VT). ICDs are generally recommended for individuals with HCM at high risk of sudden death, but risk stratification is challenging due to the limited ability to predict which patients will die suddenly. The choice between transvenous and subcutaneous ICDs depends on individual characteristics and preferences. Pacing for LVOT obstruction is primarily considered in individuals over 60 with symptoms, obstruction, and heart failure. Atrial fibrillation in HCM is influenced by genetic mutations and atrial myopathy. Ablation strategies for AFib in HCM are similar to those used in other populations and include pulmonary vein isolation and additional lesion sets depending on individual characteristics.
Keywords
hypertrophic cardiomyopathy
sudden death
heart failure
atrial fibrillation
stroke
diagnosis
treatment options
ICDs
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