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EP and the Unusual Cardiomyopathies
An Update on Arrhythmia-Induced Cardiomyopathies ( ...
An Update on Arrhythmia-Induced Cardiomyopathies (Presenter: Jason M. Garnreiter, MD, CEPS-P)
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Our next speaker is Jason Garnreiter from St. Louis, Missouri, discussing an update on arrhythmia-induced cardiomyopathies. All right, good afternoon. This has been a great session, a lot of really interesting speakers, and it's all about to go downhill for you guys, unfortunately. So I was asked to give an update on arrhythmia-induced cardiomyopathies. So sort of what are these sort of arrhythmia-induced cardiomyopathies? So this is really a situation where you have a tachyarrhythmia or frequent ectopy that results in ventricular dysfunction. And you'll see these sort of variably termed tachycardia-induced cardiomyopathies, arrhythmia-induced cardiomyopathies, arrhythmia-mediated cardiomyopathies. But what really is important here in this group is that the arrhythmia is the cause of the cardiomyopathy, not in response to the cardiomyopathy. And sort of the hallmark for these types of conditions is that the cardiomyopathy tends to resolve once you control the arrhythmia. This can be a little bit difficult to think, probably everybody in the room can appreciate that oftentimes these conditions will coexist. And you may have arrhythmias that exacerbate an underlying cardiomyopathy or arrhythmias that may be secondary to an underlying cardiomyopathy. And so you sort of get into this chicken and egg situation of which came first. Was this the arrhythmia inducing the cardiomyopathy or the cardiomyopathy causing the arrhythmia? And we're going to talk a little bit about that. So what sort of things cause this? Especially, I think, in the pediatric population, we tend to see this more with the diagnoses in which you tend to have incessant and oftentimes sort of insidious arrhythmias. This can be atrial or ventricular arrhythmias. In adult patients, atrial fibrillation is sort of far and away the most common. Although in the pediatric population, ectopic atrial tachycardia and PGRT are the most common causes. Ectopy alone can result in a tachycardia or arrhythmia induced myopathy. It tends to be seen much more in PVCs than in PACs, which sort of speaks to the point that tachycardia alone is sufficient. But in combination with some ventricular dyssynchrony, it tends to be worse and progress a little bit faster. And at least in adults, there's really not been any definite heart rate cutoff, although some studies have used heart rates over 100, 110 to sort of be part of this diagnosis. Just as an example, here's an EKG of a patient who presented when he was about three years of age with a long RP incessant tachycardia that turned out to be ectopic atrial tachycardia. Probably not surprising to anyone. He presented with left ventricular dilation and dysfunction, some mitral valve regurgitation. And this responded well to beta blockade. Here's an EKG about a year or so later on Natalol. And his arrhythmias have been pretty well controlled. And his echocardiogram has had essentially normalization of his LV function, although his left ventricle remains a little bit dilated. So why does this happen? What about these situations results in the development of a cardiomyopathy? And a lot of the information that we know about this has come from animal models, particularly models that look at rapid atrial or ventricular pacing. And so in the animal models, you can see that there's reduced myocyte energy store. So there's decreased levels of creatine ATP, glycogen, and decreased function of the sodium potassium ATPase. And patients will then sort of go on. So that's kind of the initial phase. And then patients will go on to develop cellular and extracellular matrix remodeling. There's evidence for oxidative damage to mitochondrial DNA, activation of matrix metalloproteinases, loss of normal collagen, as well as sort of elongation of myocytes and disruption of myofibrils. And that you get this decreased binding also between myocytes and the extracellular matrix. And then throughout this process, as it continues, patients will develop abnormalities in calcium cycling, which leads to defects in excitation and contraction coupling. There's also neurohormonal activation. So there's elevations in atrial and B-type nitratic peptides, activation of the reanine angiotensin aldosterone system, and decreased responsiveness to vasodilators. And then sort of later in this process, you develop LV remodeling, including dilation of the left ventricle, decreased ejection fraction and contractility. And then patients will develop increased filling pressures, LV wall stress, and systemic vascular resistance. This is a figure from a nice review that discussed this. I think it's a little bit harder in the pediatric population sometimes to know the time course, as a lot of our patients will present, and we really don't have a good sense of when their arrhythmia is actually initiated. So sort of how do you make this diagnosis? I think this can sometimes be a challenging diagnosis. The easy part, if you control the arrhythmia and the cardiomyopathy gets better, well, it's probably arrhythmia-induced cardiomyopathy. Great. Which is fine, but I think maybe is not always the best way to approach this. This is kind of a reactive rather than proactive diagnosis. You don't actually really get the diagnosis until quite a bit later in the disease process. And at onset, it can be really unclear. I do think you need to have a high index of suspicion for this. I think we can all talk about times where there was a case presented earlier today where the EP sort of was brought into the diagnosis relatively late, and it was sort of underrecognized. So you do have to have a pretty high index of suspicion. And I think especially for our adult colleagues who see sort of a veritable sea of cardiomyopathy and atrial fibrillation patients, it can probably feel a little bit like finding a needle in a haystack in terms of actually coming to this diagnosis. But I think it's really important that we get this diagnosis right. This is figures from a paper that Jeremy Moore published in 2016 looking at outcomes in patients with dilated cardiomyopathy compared to tachycardia-induced cardiomyopathy. And draw your attention to the recovery curves here. And you can see in those tachycardia-induced cardiomyopathy, pretty substantial recovery in contrast to those with dilated cardiomyopathy. So I think getting this diagnosis right can have really significant impacts on our patients. And so what tools can sort of help us make this diagnosis? So this is from that same paper that Jeremy Moore published. They looked at 80 patients that ended up being diagnosed with an arrhythmia-induced cardiomyopathy and compared to 135 controls with dilated cardiomyopathy. They looked at ECG, echo, and clinical parameters and came up with this clinical risk score. And they had two different models, one that looked at primarily echo and clinical parameters and one that looked primarily at ECG parameters and found the model that looked at ECG parameters to be more predictive and to see here with those that had three or greater than three points was considered to be high risk for the diagnosis of an arrhythmia-induced cardiomyopathy. So I find this to be really helpful. Jeremy had this great online calculator, which unfortunately has subsequently disappeared. But you can go to the actual paper and calculate this, and I find that really helpful. There's other tools. So MRI may be a useful option. This was a study published in 2012 that was in adult patients that looked at patients who presented with either frequent PVCs or ventricular tachycardia who also had decreased LV function. And then they looked at those patients who improved with arrhythmia control compared to those that didn't. And in those that did not approve, the majority of them had evidence of late gadolinium enhancement, where in those that did improve that presumably had a tachycardia-induced cardiomyopathy, only about 5% of them had late gadolinium enhancement. So MRI may be useful, I think, especially for those kids that present in incessant tachycardia. The MRI cardiologist is probably going to laugh at you if you think you can take a kid with a heart rate of 180 and get a useful MRI. But once you control the arrhythmia, maybe early on in the process, you can get that, and that can be some useful information. Electroanatomic mapping may be helpful. This is also a study in adults published in 2012. They took 55 patients with cardiomyopathy and did voltage mapping, looked at both bipolar and unipolar voltage, and found that especially in those with a high burden of low unipolar voltage and scar, that tended to suggest patients who were going to have non-reversible cardiomyopathy, presumably not tachycardia-induced, compared to those with a tachycardia-arrhythmia-induced cardiomyopathy in which they had much lower scar burden. And at least in this study, they found that a cut point, if you had 32% or more of your left ventricle with less than 8.27 millivolts in a unipolar voltage, that this was pretty sensitive and specific for suggesting an arrhythmia or a cardiomyopathy that's not arrhythmia-mediated. This was an interesting study published in 2017 that actually looked at biopsy specimens. So this had 19 patients with arrhythmia-induced cardiomyopathy that they compared to those with dilated and inflammatory cardiomyopathies, and found a few differences in those that had arrhythmia-induced cardiomyopathy. They had, actually on this study, lower levels of fibrosis compared to those other diagnoses. They also found increased expression of MCP1, which is associated with ATP generation. So these patients tended to have higher levels of ATP generation based on that expression. And they also had this interesting pattern of migration of mitochondria towards the intercalated discs, which was not seen in the other types of cardiomyopathy. So again, I don't think probably many of us are going and doing biopsies on these patients, but these are some additional tools that may help in cases in which you think the diagnosis is unclear. Sort of looking towards the future and other sort of options. So I think treatment of these conditions, most of us in the pediatric community, I think, strongly move towards a rhythm control strategy in terms of treatment. But in adults, especially for adults with atrial fibrillation, the data is a little bit less clear. Some studies have suggested a rate control strategy alone may be sufficient. There's a little bit of data that suggests actual irregularity in the ventricular rate may be a risk, even if you actually have controlled the overall rate. So some people advocate more strongly for rhythm control. There have been reports of persistent left ventricular dilation despite arrhythmia control and normalization of EF. And actually, the patient we had mentioned his left ventricle remains dilated. And somewhat concerning, there have been a few case reports of patients actually dying suddenly who have had a history of arrhythmia-induced cardiomyopathy in which they had complete normalization of their LV ejection fraction. And so the authors in that biopsy paper have actually sort of wondered aloud whether there might be some point of no return in which you have some irreversible changes that might predispose people to arrhythmias down the road, which is a little concerning. Again, I think for a lot of our patients, we may end up discharging them. And perhaps we need to keep a closer eye on them. So that's all that I have for you today. I'm happy to take any questions. Thank you. So why, if you have a teenager with a heart rate of 180 who has it because of atrial ectopic tachycardia near the sinus node and you have a teenager who has a heart rate of similar but inappropriate sinus tachycardia, why do you think the inappropriate sinus tachycardia or the POTS girl or whatever never develops cardiomyopathy whereas the other patient does? Yeah, that's sort of been discussed a little bit in some of the papers and some people have felt like it may be due to differences in autonomic tone and that patients with inappropriate sinus tachycardia or POTS may have different higher levels of sort of resting autonomic tone relative to those patients who have sort of a mismatch in their heart rate and resting autonomic tone, but I think that's not really well characterized. There has been a little bit of data that suggests some genetic factors may play an influence and that there's actually been a couple of cases that have reported angiotensin receptor polymorphisms may be related to some of this, so whether there may be some genetic factors that predispose certain patients to the development of sort of an arrhythmia mediated cardiomyopathy I think remains to be seen. Do you think that some of the patients with tachycardia and just cardiomyopathy tend to be less symptomatic at presentation and that might be like a clinical clue? That's just been my observation. That they're less symptomatic? Yeah, that's slightly crept up on them and they're used to it. Yeah, I think so. I think it's that, yeah, sort of that insidious, incessant nature of some of these that I agree. In the babies it's hard to tell, but in the older kids, yeah, I've had a number of kids that it's sort of crept up on them and that they haven't necessarily had a lot of symptoms and it may be that that's that time course and I do think the time course is somewhat variable and that you may have infants that present relatively quickly with evidence of dysfunction and there may be teenagers or other patients that that develops in a much longer term. And I wonder if some of those are maybe less reversible over time, too, that they may be later on in that cascade and they end up having more cellular apoptosis and maybe that's some of those patients that have a longer term risk that we haven't fully characterized. That was scary about the VF-MS, do you think any of those patients actually had some kind of channelopathy that caused the atrial tachycardia and was also the cause of the sudden death later? Yeah, I think that's very interesting is that might the diagnosis have been not correct necessarily at the beginning and I think a lot of those patients have not necessarily been followed so it's harder to know did they have changes or progression in their phenotype over time that wasn't fully appreciated. Thank you very much.
Video Summary
In this video, Jason Garnreiter from St. Louis, Missouri discusses arrhythmia-induced cardiomyopathies. These are situations where tachyarrhythmia or frequent ectopy leads to ventricular dysfunction. The arrhythmia is the cause, not a response to the cardiomyopathy. The condition tends to resolve once the arrhythmia is under control. It can be challenging to differentiate between arrhythmia-induced cardiomyopathies and cardiomyopathies that exacerbate arrhythmias, as they often coexist. In the pediatric population, it is more commonly associated with incessant atrial or ventricular arrhythmias. In adults, atrial fibrillation is the most common type. The development of a cardiomyopathy in these cases is due to reduced myocyte energy, cellular and extracellular remodeling, abnormalities in calcium cycling, and neurohormonal activation. Diagnosis can be challenging and requires a high index of suspicion. Tools that can help in diagnosis include clinical risk scores, MRI, electroanatomic mapping, and biopsy specimens. Treatment often involves rhythm control strategies. Long-term follow-up and close monitoring are important, as some patients may have irreversible changes and remain at risk for sudden death.
Meta Tag
Lecture ID
3461
Location
Room 203
Presenter
Jason M. Garnreiter, MD, CEPS-P
Role
Invited Speaker
Session Date and Time
May 09, 2019 1:30 PM - 3:00 PM
Session Number
S-031
Keywords
arrhythmia-induced cardiomyopathies
tachyarrhythmia
ventricular dysfunction
differentiate
pediatric population
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