false
Catalog
EP on EP Episode 106: Workup and Therapy in Idiopa ...
EP on EP Episode 106: Workup and Therapy in Idiopa ...
EP on EP Episode 106: Workup and Therapy in Idiopathic Cardiac Arrest Patients
Back to course
[Please upgrade your browser to play this video content]
Video Transcription
Hi, I'm Eric Bustowski. Welcome to another segment of EP on EP. I have a guest with me today who's a rising star in our field, Dr. Albert Sun. Welcome Albert. Albert is the associate professor of medicine at Duke and he's also the director of the inherited disease area for arrhythmias. That's right. Okay. I got it right. You got it. All right. So, so guess what? Based on all that, Al, what we're going to talk about is this, this annoying area for clinicians of the idiopathic cardiac arrest, sort of the workup and treatment is an overview. And let me start with, I guess the most important question is when do you get to call it idiopathic? So what are the things we should do before you arrive at that diagnosis? Yeah, it's a, it's a great question. And I think it's an evolving question because the true definition of idiopathic would be in the absence of anything that is clearly known, say structural heart disease, say coronary disease. And if you take the broader sense of sudden death, that's all the non-cardiac cases, but we'll stick purely for the cardiac cases. Okay. But the reason why I say it's evolving is as we know from longitudinal data for follow up of family members or people who experienced sudden cardiac arrest, what we think is the absence of a structural heart disease may blossom later down the road. Okay. But that's where it starts. Where it starts is we know for years and decades and decades and decades, we know that structural heart disease lends itself to an increased risk of sudden cardiac death. So in the absence of that, that's where the work really started, starts with trying to identify are there electrical abnormalities? Are there genetic abnormalities? Are there arrhythmia issues that are still without a clear underlying trigger or cause? And that's where that idiopathic. So let me push on it a little bit because of the workup necessary. So I would assume that you'll do a cardiac cath of most people. Yeah. Right. And then is cardiac MRI a component also of the workup? Yeah. Where it's available, I think you can think about the workup as saying, listen, we need to really hone in on the absence of structural abnormalities. So if you have cardiac MRI available, wonderful. And that would obviously be the test of choice looking for things like delayed enhancement, structure, function, so forth. Echocardiogram obviously is an easier, more available modality. But doing things like CT scans, looking for anomalous coronaries, looking for coronary disease, catheterizations, all that. So anything you can do from a structural assessment should be done. And now even more novel, looking at things like PET scans, looking for inflammation and signs of inflammatory conditions. That should be in the workup as well from a structural standpoint. So what I'm kind of getting at here is a reasonable workup before you make it. I have no problem with what you're saying, but your bill at this point is a phenomenal amount of money. Is it really necessary if you have a totally normal, let's say MRI and a normal cath and a normal ECG, do you really have to go to PET? I mean, I know some people do. If you do PET, do you have to do MRI? In other words, you're starting to layer up a lot of expense, right? Yeah. I think you're right. I think from an expense standpoint, these patients are still relatively rare. So this is not a workup that I would advocate for somebody who has plain Jane's, syncope, even though some syncope may be high risk and may be a precursor. But we're talking about people who are survivors of cardiac arrest. This is where you really are dedicating your resources to. But in regards to PET scan, I do think that that's not been shown in the initial workup. I would say specifically a PET, that may be something we add on if there's evidence of polymorphic and SVT or something that shows more of a global active inflammatory process. Got it. Okay. So let's say you do all that. We haven't talked genetic testing. I assume you do a genetic panel on everyone? Yeah. Absolutely. You know, there's great work, Andrew Kron's group, with the Casper study, which really looked at a very organized, comprehensive evaluation that includes the structure analysis, include the genetic testing and so forth. And again, sort of wide blanket genetic testing is usually what we do, because again, we're looking at idiopathic, which means that the EKG might not have been super obvious. We wouldn't have said, okay, well, someone comes in with cardiac arrest and they clearly have a type one brugada pattern on EKG. That's not idiopathic. That's a diagnosis of brugada syndrome. But you do have to start broad, and that broad would include genes that encode for structural abnormalities, cardiomyopathies, as well as the ion channels and the rhythmic genes. All right. So now you have this done, and our son goes to see him, the whole workup's been done. You found nothing, clear-cut cardiac VF documented in the field, cardiac arrest. What's your next step? So what do you do now? Yeah. Well, I'll take one step even back before that, because I do think that a lot of times we think about genetics as this super special and super complicated. There's variants of uncertain significance. There's pathogenic genes, non-pathogenic, but non-variants. By the way, I hate the BUS. Oh, I agree. Everyone does, myself included. But I think, honestly, it starts oftentimes with a good history. I mean, the fundamentals of being a physician in medicine, you take a family history, and through a really detailed family history, you start to really start to piece together, whether that's early onset pacemaker, you start to think, is this a mixed conduction disease? Is there a sodium channel variant? Is there a lamin variant or something that would predispose you? Are there super young, really, really young people with sudden infant death syndrome? Are there people who have had car accidents that were single drivers and unexpected deaths and things like that? Yeah. So that really, I'd say, even occurs before any of that fancy stuff. And we're lucky at Duke to have a wonderful genetic team, including a genetic counselor that will help us create a wonderful pedigree and where you start to piece all these pieces together. Yes, in that is definitely a comprehensive genetic testing. Well, you're lucky to have such a team. Most of us don't have that kind of a team. But, all right, so now you've done all that. There's still nothing that hits your eye like, oh my God, you know, take him to EP lab? Yeah, it's a good question. And what do you do then in EP lab? Yeah. To me, I mean, this is the way I think of it. Essentially there are going to be a group of patients that have a sudden unexplained that we made potentially just been that one in a million or billion bad luck. However, I don't believe in that as being, that's definitely a diagnosis of exclusion. I think if you look at history, when we look back, you know, 50, 70 years ago, the bucket of unexplained cardiac death was huge. And then long QT syndrome. And then CPVT. And then Brigada. Right. And then early repolarization. And then closely coupled PVCs and ventricular fibrillation. Our understanding throughout the years narrows that bucket and it's become smaller, smaller, smaller. So for me, it's to say, let's really stress the physiology. Let's stress the heart in any way we possibly can to bring out these abnormalities. And that does include drug infusions like high dose isoproteinol. In the lab now. In the lab now. In the lab, you know, certainly EP study inducibility. I don't know what that, we looked at that decades ago. Yes. You put an S4 in, you get VF. I don't know what that means. In a normal heart with a normal EKG, it's pretty nonspecific and pretty low yield. But that doesn't preclude isoproteinol at really high doses. So there is, you know, a study out of Bordeaux that looked at high dose isoproteinol to bring out PVCs in this setting or this suspicion for ARVC. Okay. But that's potentially applicable to non-ARVC. High dose isoproteinol, seeing polymorphic VT, seeing RVOT triggers, the triggers are the key I think. Meaning... Oh, sorry. No, no, it's okay. I'm just saying, rhythm has happened for a reason. So let's say you do that. By the way, I would challenge you and everybody else in this field to show me a study that a high dose isoproteinol in a person without a cardiac arrest never causes a problem. Because we've had a patient in our EP lab who had AFib who went into multiple episodes of VF and it was kind of scary for a while and finally got her out and she never had it clinically and thankfully it's never been back in the lab. So I don't know that how specific that is. So I think it's a great segue into what I truly believe. And I think that many people who suffer cardiac arrest oftentimes have an underlying predisposition. That's again the classic second hit hypothesis. So whether it's a genetic variant that is otherwise benign unless you take fluoroquinolone and have long QT, or you have some mild ischemia, or you have hypokalemia, or you have any of these various triggers including autonomics and so forth, I think that there are underlying predispositions and so forth. So that patient with AFib and VF sticks out to you because they're unusual. It has stuck out for a long time. It's unusual. But why was it unusual? It's because there probably is something different about that person. And I don't disagree with you, but trying to figure out what that is is not so easy. I agree. In the short time we have left, let's get back to your patient. You're in the lab. You produce triggers. So I assume you'll go after them with ablation? Yeah. Maybe? I'm just asking. Yeah. I think a structured way of thinking about the lab and what we're doing is we're looking for the most common causes of sudden cardiac arrest. So long QT, that means epinephrine injections, looking at the QT, CPVT. You're looking for triggers, closely coupled PVCs. Depends on the character of the PVC. Depends on the character of VT that may be induced. There's good data assert that closer coupled PVCs potentially from the Purkinje system may be much higher risk. There's data on the speed and the cycle length of VT that may be higher risk for recurrence. Ablating a PVC trigger is going to be difficult because you most likely are not having a super high burden to be able to just say, okay, I'm going to go into the lab and ablate tons of these PVCs. Most of the time these are pretty rare, otherwise it would have been potentially evident before the arrest. Yeah. Before you got to the lab. That's right. So now you're obviously going to give the patient a defibrillator. Sure. Okay. Now the last question I have for you is something that has come up with me many times over the years and I don't know how to answer it and it's always a tough discussion with the family because you get a true idiopathic and they get a defibrillator and they have two siblings and mom and dad want to know what's going to happen to the siblings. How do you handle that situation? Yeah. I think it's important in the absence obviously of a genetic pathogenic mutation that we can screen the family. It's tough. You just tell them that we don't know, but I mean, I always try to reassure them that there are electrical accidents in the world and it doesn't mean the other kids are going to get the same problem. I think that's right. I think for us the idea is being as comprehensive as possible, identifying underlying physiological traits that would predispose. In general, if you're very comprehensive, the person who presented, the proband say, who presented with sudden cardiac arrest, we have a really high hit rate for identifying an underlying cause. It's not perfect, but there is usually something that comes up. And then you can track that in the other kids. Yeah, that's right. And it's frequent screening. Usually we're looking at recommendations of every couple years, getting repeat imaging, obviously EKGs and so forth. Al, what a wonderful discussion. It's always great having you with us. Thanks so much. Thank you.
Video Summary
In the video segment, Dr. Eric Bustowski interviews Dr. Albert Sun about idiopathic cardiac arrest, focusing on workup and treatment. They discuss the evolving definition of idiopathic cardiac arrest, the importance of ruling out structural abnormalities, and the role of various diagnostic tests such as cardiac MRI and genetic testing. Dr. Sun emphasizes the need for a comprehensive approach, including stress testing and triggers identification in the EP lab. They also touch on management strategies like ablation and defibrillator implantation. The discussion concludes with considerations for family screening and long-term monitoring for potential underlying predispositions.
Keywords
idiopathic cardiac arrest
workup and treatment
structural abnormalities
cardiac MRI
genetic testing
Heart Rhythm Society
1325 G Street NW, Suite 500
Washington, DC 20005
P: 202-464-3400 F: 202-464-3401
E: questions@heartrhythm365.org
© Heart Rhythm Society
Privacy Policy
|
Cookie Declaration
|
Linking Policy
|
Patient Education Disclaimer
|
State Nonprofit Disclosures
|
FAQ
×
Please select your language
1
English