Alexander C Egbe, MBBS: Greetings. I'm Dr Alexander Egbe, assistant professor of medicine and pediatrics at Mayo Clinic. Today we will be discussing atrial and ventricular arrhythmia in complex congenital heart disease. I am joined by my colleagues, Dr Bryan Cannon, associate professor of pediatrics, and Dr Christopher McLeod, associate professor of medicine, who specializes in electrophysiology. Welcome.
Christopher McLeod, MB, ChB, PhD: Thanks, Alexander.
Managing Atrial Arrhythmia in Congenital Heart Disease
Dr Egbe: Let's start with Dr McLeod. Please, can you talk to us about medical management of atrial arrhythmia in congenital heart disease?
Dr McLeod: It is an important [issue]. There are many distinct differences in the rhythm management itself because the mechanisms are different. It's important for every general cardiologist, every internist, to realize that we don't just use standard medications.
I'm going to speak a bit about the mechanisms, because it [explains] why the medicines themselves are different. These are typically young patients and symptomatic. They have fast arrhythmias.
If you think of the non–congenital heart disease population—that group of patients who are young with otherwise-normal hearts—we usually use class IC drugs or even beta-blockade, [atrioventricular] AV nodal blockers for those. This is distinctly the approach that shouldn't be used for [congenital heart disease patients].
Because reentrant scar-related arrhythmias [occur commonly in] the complex repaired congenital heart disease patient, we want to increase repolarization and break these reentrant flutters. So, it's the class III drugs, sotalol and dofetilide [Tikosyn, Pfizer]—maybe amiodarone, depending on the patient (it's never usually our first drug)—that are specifically proven to be of use for and definitely safer in this group of patients who often have ventricular scarring.
I'm sure the audience knows that, if you're going to use a class I drug like propafenone or flecainide in anyone with ventricular scar, you can precipitate dangerous arrhythmias. [Class I drugs are] the standard approach for an adult with a normal heart. But with complex congenital heart disease, we have to steer away from those. It's an important difference.
Bryan looks after a younger population than I do, is there anything different from your [point of view]?
Bryan Cannon, MD: [Treating younger populations entails] basically the same principles and philosophies, but you have to realize that often, there's complex interactions. Sometimes there's sinus-node dysfunction and other [factors] that you have to consider whenever you're picking antiarrhythmic medications. The standard [features], like you said, of an adult after a myocardial infarction don't necessarily relate to complex congenital heart disease. [Patients] may have multiple scars, multiple circuits of flutter, sinus-node dysfunction, or other problems.
Dr McLeod: That's an important [point]. Another point I want to make sure that the fellows who are watching this understand for their training: In reentrant atrial flutters, the atrial cycle length (how long it takes for a revolution) is typically much slower than the regular cavotricuspid isthmus flutter, the typical flutter.
A slower atrial cycle length gives the AV node longer to recover; thereby, you can conduct quicker down to the ventricles. So, slower atrial cycle length, slower atrial flutters have paradoxically faster ventricular responses. That's why AV nodal blockers, metoprolol, [diltiazem] Cardizem, verapamil, don't work in this group of patients. We almost always go to an antiarrhythmic strategy. It may be drugs or ablation. That flutter that, in some patients, you can rate-control, you usually can't in this group of patients.
Dr Cannon: Dovetailing off that, one of the biggest challenges in this population is actually picking up patients who have arrhythmias. When we talk about the standard atrial flutter, that's a circuit using the entire atrium, so that's pretty easy to see on an ECG. You'll see that typical sawtooth pattern.
However, the kind of flutter that we see in congenital heart disease patients is something that we call "scar flutter," or—more properly termed—the "intra-atrial reentrant tachycardia." This is different, and it can actually fool you on an ECG because there may be periods of an isoelectric baseline or a flat baseline, and then you'll see P waves coming through. So you have to very carefully look in the T wave. You have to look for patterns to find intra-atrial reentrant tachycardia, or you'll miss it.
A couple of clues are a P-wave axis change on the surface ECG or a patient who's normally bradycardic in the 40- or 50-bpm range and has a heart rate in the 90s or 100s because, as Chris mentioned, these tend to be slower flutters, so half the battle is actually picking these up.
In addition, if you take a look on Holter monitors, if you see no heart-rate variability or you see a standard heart rate, those may be clues that you have intra-atrial reentrant tachycardia, and certainly it's easy to miss on an ECG.
Dr McLeod: Bryan just brought up a very important point, and we should have probably brought it in earlier, but these patients can present with, as he was suggesting, heart rates in the 90s or 100s. Just because patients have congenital heart disease doesn't mean that they should have a faster heart rate. They can be very well compensated [with] heart rates that are generally on the low side.
In someone with a heart rate of 90 or 100 bpm, you really need to be suspicious that there's not an underlying intra-atrial reentrant flutter. Another subtle clue would be patients doing well and not aware that they're in flutter, but ventricular function has gone down, and so they're being just too long in a slow atrial flutter, not enough heart-rate variability, and the ventricular function is decreased.
Role of Catheter Ablation in Atrial Arrhythmia
Dr Egbe: Thank you very much for this insight. Dr Cannon, can you discuss the role of catheter ablation for management of atrial arrhythmia?
Dr Cannon: I think it plays a very important role for two reasons. First of all, all of the medications have side effects. Our most effective medication that we can use is typically amiodarone. But as Chris mentioned, amiodarone has a litany of side effects, and it's not something we like to leave patients on long term. In addition, most of the other medications have some type of side effect that may be undesirable.
The second [reason] is that, on medications alone, the recurrence rate tends to be very high. [Often], we'll take them to the catheterization lab. Of all the procedures that we do, I think that these can be the most challenging. They take a long time. You need somebody with expertise, with knowledge about the basic underlying anatomy as well as ablation techniques, because the ablations that we do in these patients can be more complex because of scars, because of thickening of the atria and the ventricles, and it can make these ablations very complex.
Having said that, if you have a center that has expertise in doing ablations in congenital heart disease patients, we can have a pretty good success rate, and the advantage of that is we can avoid the patients having symptoms, hopefully help them with their ventricular function or other issues that they may be having and potentially create a situation where they can come off medications rather than having them on that long term.
The other thing we have to realize with catheter ablation is that it's not one and done. These are patients who would typically have a recurrence, and about half of patients will have a recurrence within 5 years. So, you have to be diligent even after you've performed an ablation, to make sure that it has been successful. Chris, anything you want to add about that?
Dr McLeod: Those are all important points. One thing for people to realize is that atrial arrhythmias, in their own right, aren't really that dangerous. Obviously, you don't want ventricular function to decline, but [atrial arrhythmias are] not malignant like some ventricular arrhythmias. They're not associated with sudden death. Whereas medications like sotalol, like dofetilide, do carry risks of sudden death, although they're small.
For example, you have to weigh carefully with the family the pros and cons of starting a 21-year-old with reentrant flutter on a medication that can cause sudden death for a rhythm that doesn't cause sudden death. When presented with the option of lifelong suppressive medication that [carries risk of] malignant life-threatening arrhythmias, often [the patient] would lean toward ablation.
There's one more [point] about the ablation strategies. Our approach here as a group has been preemptive ablation at the time of ablation [targeted] for a particular clinical flutter. The patient would come into the lab with a flutter or we would induce the flutter, confirm that it's the flutter that's been causing the trouble that they've needed cardioversions for, that's affected their ventricular function or symptoms.
Then we get rid of that flutter and carefully map the rest of the atrium or the atria to look for other areas that can potentially form flutter in the future. Sort of a prophylactic strategy so we don't have to come back a few years from now. A preemptive strategy of taking out the electrical milieu substrate, as it were, which really can be troublesome in the future. It does make the ablation longer, but we tell patients that it's better to have one long ablation than to come back for several successive ablations.
Dr Cannon: One of the things I'd like to add is that, typically, we think of atrial arrhythmias as causing symptoms and ventricular arrhythmias as causing sudden death, but in some of the congenital heart disease patients, atrial arrhythmias may be associated with sudden death.
So we can't say, "Well, with atrial arrhythmias, we don't have to be that concerned about them, because they don't cause problems." In congenital heart disease, as Chris mentioned, you can conduct rapidly to the ventricles, because [atrial arrhythmias] tend to be slower. There already tend to be problems with function that can result in sudden death. That's why we have to be vigilant for both atrial and ventricular arrhythmias and either aggressively treat them with medical therapy and/or ablation therapy.
Ventricular Arrhythmia in Congenital Heart Disease
Dr Egbe: Thank you for that exhaustive review of atrial arrhythmia management. We are going to shift gears a bit and talk about ventricular arrhythmias. Dr McLeod, can you discuss the different treatment strategies for ventricular arrhythmia in congenital heart disease?
Dr McLeod: It's clearly a very important [issue], and Bryan was alluding to [the fact] that the atrial arrhythmias can be malignant, which is a real [concern] in this population. Still, the most common cause of death is sudden death from ventricular arrhythmias or ventricular tachycardia.
We break them up into two categories, one of which is scar-related and similar to the atrial flutters or atrial tachycardias we've been discussing. The ventricle has been opened. These are scar-related reentry patterns. The treatment for that is similar in some ways [to treatment of atrial flutters]: you'll use a class III antiarrhythmic drug for prevention. You're also going to consider ablation, because these are often discrete isthmuses. It's one of the categories of ventricular tachycardia that is potentially curable.
That is distinctly different from the ischemic cardiomyopathy patient, from the dilated cardiomyopathy patient, where they have relentless progression of disease over time. Catheter ablation in that group reduces shocks—and even though it may reduce shocks in adults with congenital heart disease–repaired ventricular disease—it also can cure that patient of that substrate. It's not necessarily a reason not to put in a defibrillator, and it often can be a very difficult decision in a young patient where you've been able to get rid of the VT, do they still need a defibrillator or not? That decision needs to be taken carefully by the adult congenital specialist, the electrophysiologist, the family, and the patient. And considering that particular scar-related reentry. Defibrillators as therapy for ventricular tachycardia are important because it's such a big cause for sudden death or mortality in adults with congenital heart disease.
The other type of VT is a little different. It's the big bad right ventricle that's dilated, that's failing—or the left ventricle for the left-sided lesions that's failing. Here, we don't have a discrete scar-related reentrant pattern to ablate. The right ventricle, which was not built to pump to the systemic circulation in [congenitally corrected transposition of the great arteries] CCTGA, for instance, is now failing, it's dilated. There's a lot of disease substrate throughout, and we can't ablate all of that.
Defibrillators are crucial. Risk stratification, how to identify those patients we'll speak about in a minute, but it's a hard one. Class III antiarrhythmics and ablation are going to [help] avoid shocks from the defibrillator. So it's important [for patients] to be seen in a center where that difference can be understood, dissected: Does the patient need a defibrillator; do they need an ablation; do we need adjunctive medical therapy to avoid shocks from defibrillators?
Sudden Death Risk Stratification and Defibrillators
Dr Egbe: Thank you very much. Now that you've mentioned sudden death, Dr Cannon, can you talk about sudden death risk stratification and how you determine candidacy for the different types of defibrillators?
Dr Cannon: I agree completely with Chris. I think this is an incredibly important issue. The first thing that we're learning [about congenital heart disease] is, if you make a scar on the heart with an incision to fix a congenital heart disease, then at some point, you'll have arrhythmias, either atrial or ventricular.
Before, we used to think that the risk of ventricular arrhythmias and sudden death was relatively low. But as we study larger patient populations as they age, we find that that's a real risk and cause for concern. So if you have a patient who has ventricular arrhythmias, syncope, and palpitations, then you need to take that very seriously.
When we talk about treatment, although medications and ablation can have some role—predominantly in decreasing the arrhythmia burden—in sudden cardiac death, the only preventive therapy (or the best one that we have) is an [implantable cardioverter defibrillator] ICD.
The problem is that in patients who have structural congenital heart disease, we often can't put in ICDs in the standard fashion. Based on the American College of Cardiology guidelines for adult congenital heart disease,[1] if you have any mixing at the atrial or ventricular level, the recommendation is to put in an ICD in a way that's not transvenous. Especially patients who have complex congenital heart disease or single ventricles, we typically, except under very special circumstances, don't use the standard transvenous [procedure].
That puts us in a bit of a difficult situation but leaves us a couple of different possibilities. The first is that we can put in an epicardial ICD. So basically we can go into the pericardial sac, put the coil and the leads on the epicardial surface, and tunnel that to the abdomen. That way, there's nothing in the vasculature that would increase the risk of stroke or pulmonary embolus.
The second option is an entirely subcutaneous ICD that goes underneath the skin. We have to meet a specific set of criteria in order to implant those devices. But with these newer devices, patients who may not have been a candidate for an ICD previously may be very good candidates. We may actually be able to provide lifesaving therapy for ventricular arrhythmias through these devices.
Dr McLeod: One addendum to that. It is hard to know which patient should get a defibrillator and who you can avoid putting one in. You don't want to put defibrillators into younger patients, because over the years, many [potential] problems can arise, such as with infection of the leads.
Risk stratification is crucial and, as the audience knows, well-described for ischemic heart disease, nonischemic heart disease, and dilated cardiomyopathies but poorly understood for most of congenital heart disease.
The poster child of this is tetralogy of Fallot, which carries a real risk of sudden death from reentrant ventricular arrhythmias, from near the [ventricular septal defect] VSD patch, the outflow tract, pulmonary-valve replacement. Lots of isthmuses there that can lead to rapid VT and sudden death.
[In tetralogy of Fallot,] there are fairly well-described risk stratification factors and also algorithms that can be used. By and large, though, when confronted with a patient with tetralogy of Fallot, someone who's had a lightheaded spell, someone who's got palpitations, nonsustained VT on a Holter, left ventricle is looking bad, QRS is really extended—all of these are things that we really worry about in that group of patients. But risk stratification hasn't been well-characterized for most of the rest of complex congenital heart disease.
However, the general cardiologist should know that they are high-risk syndromes. Certainly, the d-transposition is one of them; CCTGA is to some degree as well. Beyond that, we don't have any risk stratification tools if someone, for instance, has a single ventricle, that's not been studied.
Dr Cannon: If you take a look at those, they are complex, [with many] factors that play a role in the decision to implant an ICD. But across congenital heart disease, the main factor—just as in adults—is [the presence of] poor systemic ventricular function. Patients who have poor systemic ventricular function are at higher risk for sudden death and arrhythmias. In those are patients you have to seriously consider ICDs earlier.
We don't like to put these devices in because—just as all patients with congenital heart disease develop arrhythmias—all ICDs will fail at some point. The leads fail. They can be difficult to place and difficult to maintain. The batteries wear out. There can be problems with recalls of the leads or the devices.
We take this decision very seriously, but we have to consider these patients in a broader spectrum. If they have known arrhythmias, poor ventricular function, symptomatic palpitations, or syncope, then we need to strongly consider upgrading their therapy and implanting an ICD. As Chris said, it's a difficult decision, requiring expertise and current knowledge of the literature. This is a moving target that changes frequently. And you need somebody who has the expertise who can put it in once you make that decision.
Maze and Preemptive Cryoablation for Ventricular Arrhythmias
Dr Egbe: Dr McLeod, can you talk about Maze and the role of preemptive cryoablation for ventricular arrhythmias?
Dr McLeod: It's important for the cardiologist who is sending these patients to the operating room. Very often, atrial fibrillation in this group of patients is not the same as in patients with normal heart-acquired heart disease, and you may not need to isolate the veins. You should have a discussion with your surgeon, who should be an expert in antiarrhythmia surgery. Often, just an isolated right-sided Maze is necessary, but that needs to be looked at carefully.
There's also good evidence that cryoablation of the outflow tract at the time of pulmonary-valve replacement for tetralogy of Fallot is not proarrhythmic and more than likely prevents VT in the future—two important things.
Dr Egbe: Thank you, Dr McLeod and Dr Cannon, for this very important insight, and thank you for joining us on theheart.org on Medscape.
Cite this: Congenital Heart Disease Arrhythmias March to Their Own Beat - Medscape - Feb 06, 2017.
