Transcript

PLEASE NOTE: While an effort has been made to correct errors in this AI-generated transcript, some mistakes may have been missed. This transcript should be taken merely as supporting material to the podcast discussion and neither is as an authoritative last word on the subject matter.

MIC CAVAZZINI: Welcome to Pomegranate Case Report. I’m Mic Cavazzini for the Royal Australasian College of Physicians. In this episode we hear about an emergency presentation to a South Australian hospital, of a 74-year-old male with shortness of breath. The curve ball is that he had undergone ablation for drug-refractory atrial fibrillation less than two weeks prior. This discussion gives an overview of developing technologies for AF treatment and developing knowledge about the possible complications. Do keep listening right to the end for some multiple choice questions to test your understanding of today’s case report. Now let me hand you over to series host, Associate Professor Stephen Bacchi.

STEPHEN BACCHI:            Hi, I'm Stephen. I'm a neurology Fellow at the Massachusetts General Hospital, and Jasmine is a sixth year University of Adelaide medical student. And today with us, we have Dr Shaun Evans, who is an electrophysiology Fellow at the Royal Adelaide Hospital. He is interested in atrial fibrillation and artificial intelligence, and is a current PhD candidate at the University of Adelaide. Thank you for joining us, Shaun.

SHAUN EVANS: Thank you so much for having me. Yeah, it's a pleasure to join the podcast.

STEPHEN BACCHI:            So as usual, we'll be discussing a previously published case report in a step by step manner, with a focus on content that is relevant to trainees and a generalist audience. So, today, we have a 74 year old male who was presented to the emergency department with shortness of breath for the last 24 hours, he's also had epigastric pain and presyncope. 11 days prior to this presentation he had an atrial fibrillation ablation for drug refractory AF symptoms. It is important to note that there are other differential diagnoses to consider in this situation, clearly. But knowing that our listenership is well versed in differentials for shortness of breath, Dr Evans, could you please talk to us about different types and methods of AF ablation?

SHAUN EVANS: Yeah, absolutely. And really, this is maybe the best time ever in history to start talking about this, because we've got more options than we've ever had. For the uninitiated, we recently acquired a new technology for AF ablation, bringing a number of methods of isolating to three energy sources. So, things have moved a lot in the last couple decades.

Really, what all these techniques have in common at the moment is pulmonary vein isolation. This the core of this really hasn't changed in the last 20 years. What we understand is that this seems to be a trigger for both initiating and persisting atrial fibrillation. This is not the only issue. So, what we find is we have reasonable success rates, particularly in the early phases of atrial fibrillation in the paroxysmal phase. But as people progress more with atrial substrate remodelling, this particular procedure becomes less effective over time, and we consider augmenting or changing the procedure slightly to try to account for this. But in reality, we don't have a perfect understanding of what we should be doing in the big picture.

That said, we do have pulmonary vein isolation, and this is very effective in the early phases. Initially, this began with the only method we had available, which is radio frequency ablation. This is essentially heating. So, we are looking to create a series of rings to isolate the pulmonary veins from the remainder of the left atrium. There are a number of ways of doing this, essentially as many different ways as you can think of to draw circles around the pulmonary veins.

But about 10 years ago, we were introduced to a new technology called cryoablation, and so rather than a heating technology, now we're freezing. So, this, quite literally, is a balloon filled with liquid nitrogen, which we place at the ostium to each of the four pulmonary veins in sequence. And we chill it with liquid nitrogen to very cool temperatures, watching for electrical isolation much in the same way we do with thermal energy.

And more recently, in the last five years, we have something called pulse field ablation, where instead of a thermal heating energy or a cooling energy, I suppose you could call it, although that's not physically correct, we use very high power, very high power electric fields applied to that region of the pulmonary vein to achieve something called electroporation.

JASMINE LE:       Great, thank you. So, this patient had cryoballoon ablation to isolate the pulmonary veins. This was performed under general anaesthetic while on uninterrupted rivaroxaban. A transesophageal echocardiogram confirmed there was no left atrial thrombus, and assisted with transeptal puncture. After the procedure, a transthoracic echo demonstrated no significant abnormalities. He was discharged after an overnight stay and reviewed in clinic one week later. Four days prior to presentation, revealed no arrhythmias, and another TTE showed trivial pericardial separation. Now, while we don't want to anchor too early, it does seem possible that we may be dealing with a complication of AF ablation here. Could you please talk to us about the type of complications that might occur with AF ablations?

SHAUN EVANS: Yeah, absolutely. So, I suppose the first thing to mention here is that a trivial pericardial separation is quite a normal finding. Many people have this outside of an AF ablation and so, this doesn't necessarily push your radar up for a complication, but it is a great jump off point. So, yes, absolutely, pericardial effusion and the possibility of tamponade is still one of the feared complications of AF ablation, and the rate of that still approaches approximately 1in 200 patients. It has gone down in recent years as 3D mapping and catheter technologies have changed, allowing us to be more deliberate and delicate in the atrium. But still, unfortunately, can occur.

In general, we would divide our complications, I suppose, into anaesthetic and cardiology procedure-related complications. And within that, we would talk about access-related complications, so vascular complications. And then we have the complications that are really related to mechanical manipulation in the heart. So, access to the right atrium, the possibility of perforation and tamponade transept or puncture, the possibility of perforation into the aorta or posteriorly out through the rear of the right atrium. we have the possibility of thrombus formation. Now some might reasonably remember that some of this relates to heating energy. So, higher temperatures increase the rate of thrombus formation, but simply having a catheter in the left atrium can be thrombogenic.

So, we do still talk about dwell time and levels of anticoagulation during the procedure. In fact, even looking at the three different energies, one of the things we still do is uninterrupted anticoagulation and the addition of heparin during the procedure to try to minimize this stroke risk. This is one of the ones we worry about the most. The rate is, again, still about 1 in 200 using these newer methods, to try to avoid it.

Then we also have what are considered, perhaps the more specific complications of AF ablation. These are some, perhaps some of the more feared complications as they occur a little bit later. This is atrio-oesophageal fistula, which usually presents a few weeks after the procedure, which is where we get communication between the left atrium and the oesophagus itself. Now, typically this is brought about because of thermal disruption to the layers between them allowing passage and, of course, is a surgical emergency. We also worry about something called pulmonary vein stenosis. Typically, this occurred with heating energies, so radio frequency energies, where ablation within the ostium of the vein allowed for growth inwards and obstruction to flow returning from the lungs to the heart. Thankfully, we see this less commonly now, as ablation lines and techniques have changed, but it is still something we worry about and still something we see from time to time.

Then perhaps the last complication to mention before we move on is the late complications which can occur after ablation, and these are predominantly electrical. So, we talk about the procedural success, failure rate, recurrence rates. Unfortunately, this is a condition which, either through ablation techniques or through patient risk factors, can reoccur over time, as well as reoccur in ways, perhaps, which change based on the ablation that is done. So, we see things like atrial tachycardias and left atrial flutters, which can occur as the result of ablation lines within the atrium. The change in electrical activation allows new circuits to be formed.

STEPHEN BACCHI:            Okay, so we have some possible complications now, to keep in mind, we'll proceed to the physical examination. So, for our patient in the emergency department, his heart rate was 104 beats per minute, and his blood pressure was 100 over 50. He's an elevated JVP and muffled heart sounds. His ECG showed a sinus tachycardia with up-sloping, widespread ST elevation and reduced pre-cordial QRS amplitude relative to the pre-ablation ECG. Now this is bringing to mind some multiple choice questions that involved an eponym of Beck’s triad for me, Dr Evans, could you please talk us through the significance of the physical examination in ECG findings and what's most likely happening here.

SHAUN EVANS: I mean, this is why we write case reports, right? Because, once in a while we get an amazing clinical exam that points us in the right direction. In this case, yes, Beck’s triad; hypotension, jugular venous pulse distension and muffled heart sounds are the classical findings of cardiac tamponade. And while not the only possible causes of these findings, certainly, given the procedure this patient has had, has brought it to mind.

We see here that the patient is tachycardic, which is not a good sign, if this is sinus tachycardia. We see up sloping, widespread ST elevation, which usually points us at a problem in the pericardium or the myocardium. Now, given that the patient's recently had an ablation, we're concerned there's either been myocardial disruption and perforation or pericarditis. Now, as it turns out, if you see this particular finding after an ablation, the mechanism is usually inflammatory. Because if you have a perforation or a micro perforation, it usually presents a little sooner than this, whereas something inflammatory may take a week or two to develop. So, this is a relatively late presentation of these findings.

We also see reduced QRS amplitude, another fantastic finding, if you see it. This is a sign that the electrical signal has somehow been impeded or disrupted from its journey from the myocardium to our ECG electrodes on the skin. And while there is a relatively wide number of causes for this, the things that come to mind after ablation are certainly the addition of extra fluid in the pericardial space, or, I suppose, a pneumothorax, which is quite a rare complication of AF ablation. Both of these would certainly be on my mind. Now, putting all of this together, we have signs of perhaps, pericarditis, signs of perhaps, tamponade. I am now worried that this patient's having an inflammatory pericardial effusion, and is on the way to haemodynamic instability.

JASMINE LE:       Okay. So, with that in mind, a TTE was performed, which demonstrated a large circumferential pericardial effusion. There was collapse of the right atrial and right ventricular free wall. Urgent pericardiocentesis was performed. This resulted in the drainage of approximately 600 ml of serous fluid. So, now that the cardiac tamponade has been treated, treatment directed at the underlying pericarditis will be required, right? Could you please talk to us about the treatment of pericarditis, acknowledging that the treatment will differ case by case?

SHAUN EVANS: Of course, yes. So, this patient, being haemodynamically unstable certainly needed a more immediate treatment. And so this resulted in Pericardiocentesis in general. This is something that we reserve for patients who are haemodynamically unstable, although there are, of course, situations where we may perform it otherwise. So, most pericarditis is inflammatory in nature, and so the treatment is anti-inflammatories in most situations. We found colchicine to be the drug of choice these days in treating pericarditis although prednisolone is a reasonable alternative. It is used a little less commonly these days, mainly related to some data, which showed a number of years ago in pure inflammatory pericarditis, that recurrence rates seem to be a little bit higher with steroids than they were with colchicine, as well as the ability to potentially avoid side effects associated with steroid use, even if it is short term. So, those are our two main drug options.

Then when we look at the pericardial fluid itself, usually we like to see this settles down. So, in the most common cases, we treat a patient with anti inflammatories. If the pericarditis is associated with pericardial fluid, we'll usually follow them with serial echocardiography until we see resolution. This serves two purposes. One, it makes sure the patient isn't getting worse and heading towards a delayed or a tamponade situation. But two, it also allows us to monitor for a rarer complication still following pericarditis, and that is constrictive pericarditis, which can be quite difficult to spot unless you know you're looking for it. So, in this situation, yes, the pericarditis was treated, but the patient was haemodynamically unstable, and so we proceeded to pericardiocentesis.

STEPHEN BACCHI:            Great. Thank you for that summary, Dr Evans. So, this patient received 25 milligrams of prednisolone daily for seven days, and his rivaroxaban was also interrupted for three days. The pericardial fluid just revealed an inflammatory pattern in red cells. He recovered well, with no further arrhythmia or effusion, so, it's a good outcome for this patient. However, it does highlight that procedures like AF ablation can come with significant risks, and minimizing the risks associated with this is important, and one development that you mentioned before in AF ablation is pulsed field ablation, or PFA. Could you please summarize for us the current state of the evidence around PFA and its possible costs and benefits?

SHAUN EVANS: So, this is our most exciting new development in atrial fibrillation technologies, so it's hard not to be a little bit excited talking about PFA. This is hopefully going to reduce complications for us further, and it also holds some promise of reducing procedure times. If you remember when I was talking about complications, PFA is still going to have some of these, right? Anaesthetic complications may change a little bit if procedure times come down. Access complications are still an issue. Now, while these still occur, they are far less common these days, as most centres have moved towards ultrasound-guided femoral vein access, which has reduced complication rates in broader registries.

When it comes to mechanical complications, this is still can be an issue. So, mechanical complications are really a function of what catheter you have in your hand, how long you're spending in the atrium, and how well you know where it is at any given time. Now we can see where we are either through fluoroscopy, that is x ray, or with 3d mapping systems. And, typically, both of these are available to us for PFA, although certainly 3D mapping is not necessarily required. By using these and by the force feedback on the catheter, we're generally able to have a good sense of where we are to try to minimize injury, but getting the procedure time down helps further still, because the longer we spend in the atrium, the more likely it is that we potentially run into problems.

Now, the real promise with PFA is really when we get to specific complications. Things like pulmonary vein stenosis and atrio-oesophageal fistula. So, far, these really haven't been seen with PFA, with pulse field ablation. Now, I have to make note that these are quite rare complications, even at the worst of times, so, it's going to take a little while before we know for sure where this risk profile sits compared to radio frequency and ablation and cryoablation. So, for example, atrio-oesophageal fistula, while it's one of the complications we fear most, the rate really is about one in 12,000, to one in 30,000 for radio frequency ablation, and probably that's come down over the years. If you recall me talking about force-sensing catheters and 3d mapping and how that's changed things for us.

We also have technologies to try to protect the oesophagus. A number of things have been tried over the years, but perhaps the things that matter most are now considering how we apply energy to the posterior wall of the left atrium. So, there are people who will choose to use higher energies for shorter periods of time. There is somewhat complicated physics involved there regarding conductive heat transfer from the left atrium into the oesophagus, but also the idea that we have a thermal probe in the oesophagus now to monitor temperature. So, this has all resulted in the risk being much lower than it used to be.

Now we thought at one point we wouldn't see this at all with cryo balloons, but it turns out we do, just very rarely. The rate, according to the global registry, is about one in 25,000. So, you can imagine that we're going to need tens of 1000s, if not hundreds of 1000s of cases of PFA before we really know exactly what the risk profile will be for these rare complications. But so far, this is looking really good. In terms of success, the three technologies are all very similar at the moment, so really, we now have some choice and some individual discretion as the best way to go forward to perform an ablation for these patients.

This will continue to develop over time, of course. And while PFA is a new technology, it is somewhat more expensive, considering the equipment costs, compared to a radio frequency generator, which is available in all our electrophysiology labs. But the benefit is that it's really changing access and procedure time. And so this is causing a shift where perhaps more atrial fibrillation ablations can be done in a given day, which means that more people are able to be treated, and access to treatment and access to ablation has been an issue probably for at least the last decade for us.

JASMINE LE:       Right, thank you, Dr Evans, so to wrap up the case for listeners, could you please outline a couple of key learning points or take home messages that Trainees could take from this case?

SHAUN EVANS: Of course. So, for our trainees, we would love for you to recall Beck’s triad and ECG findings consistent with pericarditis and indeed, tamponade when you get electrical alternans as a finding we didn't discuss in this paper, but something to be aware of for your MCQs. But when we think about AF ablation, perhaps the best thing to be aware of at the moment is the complications both immediate and delayed from AF ablation, and how these can be categorized relatively neatly by the portion of the procedure they relate to, as well as, to some extent, the energy modality by which we're doing the AF ablation. So, cardiac tamponade and pericardial effusion, while they are most commonly an early complication, if not a day of complication for AF ablation, they can occur in these delayed settings, and this is typically through an inflammatory mechanism, which is worth keeping in mind, mainly so that diagnostically, we're not inclined to shut off too early to possibilities when a patient presents unwell to the emergency department,

STEPHEN BACCHI:            Fantastic. Thanks, Dr Evans, so that's been a really useful case for me. I found that really educational. I hope our listeners have as well. So, for full details, they can refer to the article that was titled Delayed cardiac tamponade from pericarditis following pulmonary vein cryo-balloon ablatio which was published in the Internal Medicine Journal in 2020.

the first author, Dr Shaun Evans, who's joined us today, and the senior author, Prof Prash Sanders. And now, Dr Evans, I just got to take the opportunity. I know that you have an interest in artificial intelligence, and I mean, everywhere we look, right now, artificial intelligence is making the news, and I was fortunate to collaborate with you on some very interesting cardiology AI research. I wonder if you could just give us your thoughts about the current state of artificial intelligence and where you see it going kind of the near future. What makes you excited about it?

SHAUN EVANS: Oh, I love it. So, while we can be excited about pulse field ablation and newer technologies for AF ablation, perhaps AI is going to be our next industrial revolution in medicine, and maybe even more broadly than that. I think it's got so much potential to change workflows. We are seeing it crop up everywhere. So, to give you a real world example, just Monday morning, our research group was discussing a paper that was just published which talked about the use of AI to guide atrial fibrillation ablation strategies.

And so, AI has so many applications for us. The case is really figuring out where it's going to perform well and where it's going to help us do our jobs better. So, particularly in the electrophysiology, in the EP space, there's really two avenues I see for us as truly exciting. The first is in signal analysis.

A lot has been done with traditional signal processing algorithms in the EP lab to try to improve our ability to see what is going on electrically inside the heart. But often this falls somewhat short and it ends up relying on the physician's eye to see what's going on in real time on the screen. Now this seems like a perfect opportunity for AI to get involved and help highlight areas which may be potential targets for ablation, or what we call a critical isthmus in an electrical circuit.

So, this is part of the theory that went forward in this paper I just mentioned about AF ablation strategies, where the electrograms, or the EGMs, we call them, were fed into an AI machine to provide the physicians with locations to target in AF ablation. And in fact, it was very successful in acutely terminating atrial fibrillation during ablation procedures.

The other side of AI and we can speak more broadly than EP now is to talk about language processing and how that's going to affect all of our workflows. This is not just consulting, but this is on the ward round as well. What opportunities will language models provide us to perhaps pick out details in patient histories that we should have been attuned to and weren't. To guide us with additional questions, especially if you consider disciplines that we don't do in our day to day practice, and how it might help us identify problems sooner. As well as, of course, the reduction in workload and documentation that I think we're all hoping for, and maybe this has been the most talked about thing about AI and language models in the hospital.

STEPHEN BACCHI:            Fantastic. And I could recommend multiple articles by Dr Evans, but I've got to plug one more Artificial intelligence age prediction using electrocardiogram data: Exploring biological age differences published in Heart Rhythm in 2024 was fantastic read, if I don't say so myself.

SHAUN EVANS: So kind of the co-author.

STEPHEN BACCHI:            Hah, Thanks again.

MIC CAVAZZINI: Before we go, we’re introducing a bit of an easter egg to these Case Reports. A quick quiz question to see how closely you’ve been listening. What are the three signs known as Beck’s Triad that are strongly suggestive of cardiac tamponade?
I’ll let you think about it before giving you the MCQ options. For this contribution I have to thank Dr Deniz Tuncer, a basic physician trainee in Melbourne who has recently joined the podcast editorial group.

Okay, let’s hear the possible answers he has provided to the question, what are the three signs known as Beck’s Triad that are strongly suggestive of cardiac tamponade?

Is it (A) Hypotension, muffled heart sounds and Kussmaul’s sign
(B) Hypotension, muffled heart sounds and jugular venous distension
option (C) Hypertension, muffled heart sounds and jugular venous distension
or (D) Hypertension, pulsus paradoxus and Kussmaul’s sign

Have you picked one yet? That answer is (B) Beck’s triad consists of hypotension, muffled heart sounds and jugular venous distension. These are classic signs of cardiac tamponade due to pericardial fluid accumulation which impairs ventricular filling.

Many thanks to Deniz Tuncer, Stephen Bacchi and Jasmine Le for putting their effort into this resource for Trainees, and to the other members of the editorial group who took a listen to early drafts. Please remember that this is out of their own spare time, and it should not be taken as the last word on the topic. Hopefully you found it useful, please share it with your peers and send any feedback to podcast@racp.edu.au. We’re always happy to take suggestions and to showcase research from RACP members through our Journal Club podcasts.

At the web page racp.edu.au/podcast there are links to other resources and plenty more episodes. You can subscribe through any podcasting app just by searching for the name Pomegranate Health. This podcast was produced on the lands of the Gadigal clans of the Yura nation. I pay respect to their elders over tens of thousands of years. I’m Mic Cavazzini. Thanks for listening.