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EP and the Unusual Cardiomyopathies
Skeletal Myopathies With an Arrhythmia Phenotype ( ...
Skeletal Myopathies With an Arrhythmia Phenotype (Presenter: Naomi J. Kertesz, MD, FHRS, CEPS-P)
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Our next talk will be by Naomi Cortez from Columbus, Ohio, discussing skeletal myopathies with an arrhythmia phenotype. Thank you very much, Dr. Davis and Dr. Shetty. So I'm going to discuss on a very clinical, non-basic science level the skeletal myopathies and arrhythmias and what we as electrophysiologists need to know. So what are we going to talk about? We're going to talk about Duchenne and Becker muscular dystrophy, type 1 and 2 myotonic dystrophy, Emory-Dreyfus, fascoscapulohumeral, and the limb-girdle muscular dystrophies, and finish up with Kern-Sayer syndrome. To give you sort of an overview of the incidence and the onset, Duchenne muscular dystrophy is the most common muscular dystrophy. You'll see that the Duchenne, Becker, fascoscapulohumeral, and the limb girdles all have onset. In adulthood, and then the Emory-Dreyfus also has onset in childhood, but only occurs in one of 100,000 people. The myotonic dystrophies are much more common in adults and are much more common muscular dystrophy. So the big picture from us as electrophysiologists is each of these diseases manifests as either a cardiomyopathic, conduction abnormality, or arrhythmias. The Duchenne and Becker muscular dystrophies predominantly have the cardiomyopathy phenotype, whereas the myotonic dystrophies have much more conduction abnormality, as well as the Emory-Dreyfus. So to take a deeper dive here, we're going to start with Duchenne and Becker muscular dystrophy because, as I said, it is the most common form of muscular dystrophy occurring in one of every 3,000 alive births. It is an X-linked disorder caused by mutations in the dystrophin gene. Duchenne muscular dystrophy is characterized by the absence of dystrophin, whereas Becker muscular dystrophy shows dysfunctional or shortened dystrophin. So they're really the same disease, but spectrum of the same disease. The incidence of arrhythmias does seem to correlate with the severity of cardiomyopathy. However, the severity of the cardiac disease does not correlate with the severity of skeletal disease. And this can be a mistake made by your neurologic colleagues, that they don't refer them to cardiology until they're manifesting muscle disease, and they can already have sustained significant cardiac disease. From an arrhythmic standpoint, persistent sinus tachycardia is the most common arrhythmia seen. Nobody knows why that is, but it is seen throughout both Duchenne and Becker muscular dystrophy. Atrial arrhythmias are uncommon, but you can see atrial flutter and fibrillation. Ventricular ectopy, composing mostly of PVCs and couplets, occurs in 30% of patients and correlates with a decreasing ejection fraction. Sudden death occurs, but how much is cardiac versus respiratory is really unknown. So we put together an international registry and have data from nine centers in four countries of patients with Duchenne and Becker muscular dystrophy with an EF of less than 55%. Up till now, we have 124 patients with an average age of 21 years and a mean EF of 37%. Forty-nine patients have an EF less than 35. Nine patients had ICDs placed, seven of whom had an EF less than 35, and none received a shock. Twelve patients died, three who had ICDs in place, none were arrhythmic in etiology. Six patients who had VT also died, five with EF less than 35, none arrhythmic. Which raises the question, do the adult guidelines for ICD implantation in all patients with an EF less than 35 apply to this population? Now if you're going to decide that you are going to go ahead and put in a defibrillator in one of these boys, understand this is not going to be your simple shock box. Most boys with Duchenne muscular dystrophy are afraid of being intubated and want conscious sedation. They are difficult to sedate and have difficulty lying flat. The muscle in Duchenne and Becker muscular dystrophy is replaced by fat, making finding tissue planes difficult. If you look at this slide here, you'll see this is what the color of the muscle is in patients with Duchenne muscular dystrophy. So if you're dissecting through the fat and waiting until you hit the pink muscle, well you'll probably hit the ribs before you find any pink muscle. Most of these boys also have significant scoliosis, so can't lie flat and make it very complicated for anesthesia to sedate them. Also this isn't just a normal heart. Remember that the body that these poor boys live in, many of them have this significant contractures. So here you can see this is actually the right hemidiaphragm in this patient. This is the bowel extending over here in the other patient. So many times when I'm placing devices in this population, I will actually take an angiogram when I get access to better delineate where I'm going. So to move on to Emory-Dreyfus muscular dystrophy, this is an X-linked recessive type. It's seen in childhood. It has mild skeletal involvement, but it is coupled with life-threatening conduction abnormalities and arrhythmias. Atrial fibrillation and flutter and atrial standstill can be seen in all three of Emory-Dreyfus muscular dystrophies, making anticoagulation an important decision, understanding that using CHAD scores does not apply to this population. Sudden death is the most common cause of death, and risk factors include non-sustained VT, an ejection fraction less than 45%, Lamin-AC, nonsense mutations, and male sex. ICD rather than bradycardia protection alone is preferred in this population. I'm going to go through with you a patient of mine who is a 14-year-old with Emory-Dreyfus. This is his resting ECG on a beta blocker. You can clearly see those very large and distinct P waves, so I'm going to zoom it up here. Here are these wonderful little P waves. He's in an incessant atrial tachycardia. Unfortunately, he is both bradycardic and tachycardic on medical therapy, making him difficult to manage. So since it seemed like he had one predominant atrial tachycardia, we decided to take him to the cath lab to see if we could potentially ablate this. And well, this is what we found. You can see in the turquoise, this is a pentory catheter in the right atrium. The green is in the coronary sinus, and the yellow is in the hiss. I will point out that he did have a normal HV, which is an evaluation of his conduction, but he clearly does not have a normal atrium. We actually did voltage mapping, and here the red shows voltage of less than 0.1 millivolts. You can see, even at age 14, what a diseased atrium we are dealing with. So to move on to the limb-girdle muscular dystrophies, these muscular dystrophies are grouped together because the patient's manifest weakness in limb, shoulder, and pelvic girdle distribution. There's a heterogeneous inheritance of multiple different abnormalities in genes, and it affects different proteins and enzymes. So anything that's autosomal recessive is a 2, and anything that's autosomal dominant is a 1. You can see there are types 2A to 2P and 1A to 1H, and that's as much similarity as they have to each other. But what we do know about them is arrhythmias are related to the specific subtype with a high incidence in subtype 1B. These patients are at risk of sudden death, and again, it includes non-sustained VT, LVEF less than 45, male sex, and Lamin A C nonsense missense mutations. Very reminiscent of the Emory-Dreyfus patients, these patients have a different prognosis, and it's very important to make sure that you have the right specific diagnosis. Patients with the limb-girdle muscular dystrophy 2I are at risk of cardiomyopathy and actually have a phenotype much similar to the Duchenne and Becker muscular dystrophies and really should be followed the same as you would those muscular dystrophies. Myotonic dystrophy 1 and 2 is the most common muscular dystrophy presenting in adulthood. Myotonic dystrophy 1 typically has an earlier and more severe cardiac involvement. There is a congenital form of myotonic dystrophy. However, these patients usually don't demonstrate cardiomyopathy or arrhythmias in childhood. However, their parents, who may only have a mild skeletal abnormality, may not have been seen by cardiology, and it's very important that their parents see cardiology as their arrhythmias may be a problem already. The cardiac pathology involves degeneration, targeting the conduction system with the most common finding being a prolonged HV, which can progress to AV block. Asymptomatic patients want close monitoring as their AV block can follow an unpredictable course. Atrial fibrillation and flutter are common, and up to one-third of patients with myotonic dystrophy type 1 die suddenly, some of which has been reported to occur in patients with pacemakers, making the question of whether they need defibrillators rather than pacemakers. So the rest, fascio-scapulohumeral muscular dystrophy is the third most common muscular dystrophy. It is autosomal dominant. It is not something we have to deal with much because significant cardiac involvement is rare. I wanted to mention Curran-Sayer syndrome, which is a mitochondrial myopathy because these patients also have an onset before the age of 20, and they have conduction system disease that has an unpredictable course with up to 20 percent of patients dying suddenly. So in conclusion, the muscular dystrophies are a diverse group of progressive diseases. Life expectancy is getting longer in DMD, Duchenne muscular dystrophy, even with patients living into their 30s, which is resulting in more patients with significant heart disease. The ICD indications in this population are unclear. The degree of skeletal disease does not correlate with the severity of heart disease, and it's important to realize that arrhythmias as well as conduction disease are seen. The pacemaker and ICD indications are different in these patient populations. Unfortunately, there should be a heart rhythm consensus guideline that should be published later this year. Thank you. So is that guideline going to have, it's going to have, be about children mainly? No, actually it's going to be, it's a combined. It's going to be both adults and children because of the myotype. It's going to encompass all the muscular dystrophies. Yeah, so that'd be very good to have some guidance because it's very complicated to decide what to do. Questions? Thank you very much. There's one question. I've implanted a couple of defibs, CRTs actually, in patients Duchenne, and I completely agree with all your comments, but there was a question of, none of them have had shocks, and it does seem when you look at the retrospective data on defibs in Duchenne, they don't get shocks. I've got a couple of others coming up I need to implant. I'm thinking I should probably implant a CRTP, not a CRTD, and I would value your thoughts on that. So I think it's a very difficult conversation because if you look at dilated cardiomyopathy and the adults and children, if you look at SCUD-HEFT, which all the guidelines are based on, the average age is 55 to 60. So if you look at dilated cardiomyopathy from the cardiomyopathy registry, you'll find that the incidence of sudden cardiac death in young age group is much, much less than it is in their adult counterparts, and I think that's what's raising the question of, do we really need to put defibrillators in these boys? This is both a retrospective and prospective study that I would love for you to join if you have ICDs in your patients with Duchenne. I think it's a conversation with them. I don't have a good answer for you. I will tell you that I don't use an EF of 35 to put in a defibrillator, and so it is really, as their function continues to progress, if they're having a lot of ventricular arrhythmias, I will present it. I think that this population very much brings up the end-of-life issues, because if before you put this device in, you need to discuss when or how you're going to turn it off, and what their long-term desires are, and I think that this population, more than others, really requires you to sit and have a long conversation with them. I think that's it. Thank you.
Video Summary
In this talk, Dr. Naomi Cortez discusses the relationship between skeletal myopathies and arrhythmias. She focuses on various forms of muscular dystrophy, including Duchenne and Becker muscular dystrophy, Emery-Dreifuss muscular dystrophy, fascioscapulohumeral muscular dystrophy, and limb-girdle muscular dystrophy, as well as Kern-Sayer syndrome. Dr. Cortez highlights the incidence and onset of these diseases and their manifestations as either cardiomyopathic, conduction abnormality, or arrhythmia phenotypes. She also discusses the challenges and considerations in implanting defibrillators in patients with muscular dystrophy. The talk concludes by emphasizing the need for guidelines specific to this population.
Meta Tag
Lecture ID
3459
Location
Room 203
Presenter
Naomi J. Kertesz, MD, FHRS, CEPS-P
Role
Invited Speaker
Session Date and Time
May 09, 2019 1:30 PM - 3:00 PM
Session Number
S-031
Keywords
skeletal myopathies
arrhythmias
muscular dystrophy
cardiomyopathic
defibrillators
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