Click here to view next page of this article

 

Cardiac Arrhythmias in Children

Signs of arrhythmia is irregular rhythm with normal P-wave and normal P-wave axis meaning that itís coming from the sinus node. It has a gradual lengthening and shortening with a variable P-P, but you can have escape beats. So you can have such a vagotonic situation that you can end up with depressing the sinus node and having junctional escape or even ventricular escape if the vagotonia is acting strongly on the junction itself. We really donít treat unless itís severe and associated with symptoms of sinus node dysfunction. Certainly vagotonia in the presence of sinus node dysfunction can cause some symptoms.

As you can see here we even see a baseline change here with respiration, with inspiration, expiration and the variable P-P. PACís, thereís a premature P-wave and most of the time you can find it or infer it, as weíll give examples in a moment. Usually you have a different P-wave axis because most of the time it comes from areas away from the sinus node area, but some times it can come from the sinus node area and it can look like a sinus node beat thatís coming premature. Variable PR interval exists because it depends on when and how early the P-wave occurs as to how the AB node is going to accept that prematurity.

Clinical situations? Almost always PACís are normal, but occasionally we see those patients who have PACís because they have an irritable atrium and infants who have the deadly high-mortality problem disease of myocarditis, can present with PACís.

Now PVCís are the differential diagnosis if they are different or aberrant. We also occasionally see a wandering atrial pacemaker - actually fairly common on Holter monitors - that we see changing P-waves. They can come in early it looks like because of the sinus arrhythmia and sinus arrhythmia itself. Most of the time we donít treat and if there is a problem and we know what it is we will treat the cause. Especially if itís associated with the onset of SVT. If that is the initiating event of SVT then we will center our treatment on that particular problem. Now into PVCís. Premature again.

We donít see P-waves at appropriate intervals. Abnormal QRS configuration. Notice that I did not say aberrant or wide because in pediatrics, as compared to adults, all it need to be is different because the conduction system of the ventricle including the bundle branch system, the Purkinje system and the myocardial conduction itself does not necessarily have to be a wide or long QRS. It can be different to be aberrant or coming from an actual PVC. Basically they are the same group that I just noted for PACís. Most PVCís in children are normal. But occasionally they can be from the other things we just described. The differential diagnosis is aberrant conducted supraventricular beats, almost always itís a PAC. There are very very few times when you actually have a premature junctional beat. So our job, when we see PVCís, is to try to decide is it a benign problem.

What do we do? Once we declare that the patient has benign PVCís, we donít treat. We may not completely dismiss them from follow-up. It depends on how frequently they have the PVCís. We have had occasional patients who have tens of thousands of normal PVCís on a Holter monitor recording in 24 hours that have developed over years and years and years, have developed dilated cardiomyopathy in response to having all of those PVCís. In most patients, if we follow them closely and we pick that up - as far as a echo dilation or dysfunction problem - and we intervene and we control the PVCís, most often that problem of the LV dilation dysfunction disappears with treatment. So we do follow them if we see multiple, but if there are just a few thousand and completely asymptomatic, we are likely not to follow them in the future. If we find that they are potentially serious -and thatís what Iíve defined as malignant - we treat the underlying cause. Acutely in the ICU, Lidocaine is still the drug that we use predominantly. Procainamide occasionally now that IV Amiodarone is out we may use that if there is non-sustained ventricular tachycardia in conjunction with the PVCís. Occasionally we will use something like atropine or pacing to increase the heart rate to over-drive a bradycardia-dependent PVC. In other words, we decrease the time for which the PVC can occur and then the PVCís can then be controlled in that fashion in an acute situation. Chronically, beta-blockers are what we use most often. Mexiletine is right up there and amiodarone orally along with Dilantin in some of the patients who have responded well in the post op heart disease group.

Okay, now for supraventricular tachycardia for the remainder of the time. We are going to define this as a rapid, regular and, in pediatrics, itís usually a normal QRS duration. Itís usually not aberrant. Itís usually not different than the underlying sinus rhythm QRS. Occasionally it is and when it is it is almost always at the onset of the tachycardia, and then after the bundle branches become accustomed to the higher rate, the aberrancy usually goes away. So that is a difference between pediatrics and adult where you will see a lot more aberrant supraventricular tachycardia on a sustained tachycardia, as opposed to going away, the

The clinical situations? About 15% have abnormal underlying heart in children; 85% or greater or so will have an otherwise normal heart. Wolff-Parkinson-White syndrome (WPW) occurs in about 25% and weíll go a lot more into detail about that in a little bit. Underlying congenital heart disease is about 15%. Of all the congenital heart disease types, Ebsteinís is by far is the most noted for having WPW and tachycardia, as opposed to all of the other types of congenital heart disease. Hyperthyroidism, we always look for and are always concerned about it and it certainly can be an exacerbating cause for the onset but we donít

Sinus tachycardia, to help distinguish between SPT. Notice that there a P-wave in there. On this particular example in this baby a heart rate of 220 beats per minute. Donít forget that sinus tachycardia in babies can get up to 230. The highest I have seen in a baby is about 255 beats per minute. That was very difficult to distinguish between an abnormal tachycardia. But it can

Now this slide, Iím going to take you through, in a sinus rhythm what pre-excitation and WPW look like as well as an example of whatís so-called concealed WPW. (Trans. Note: Wolff-Parkinson-White syndrome) First on the left I have a normal example. The format that Iíve depicted here, the illustration, is that we have the sinus node on the right, we have the lines through here. This depicts the mitral valve thatís closed. This is the tricuspid valve, the right and left bundles in respective ventricles. So as we see here the sinus node emits an impulse. Itís not picked up on the surface EKG unless the atrium of course is depolarized and then the P-wave occurs. From that point to when the ventricular depolarization occurs, all of this is silent on the

Concealed accessory pathway means that a pathway exists but for one or two reasons, there is not the pre-excitation that occurs. One reason, the most common reason - and we donít understand exactly why - but the pathway is not capable of conducting from the atrium to the ventricle. So no matter how close you are, even if you have a catheter over here and you are

The most common by far is ortho-dromic reciprocating tachycardia. We call it ORT. Some people call it AV reentrant, atrioventricular reentrant tachycardia, where the pathway of the tachycardia goes down the normal and up the abnormal and goes around and around and around. Now the initiating event for starting it can be sinus tachycardia during exercise, it can be

Anti-dromic occurs in about 5% of patients. Now this is the true, regular, wide QRS tachycardia. It looks exactly like ventricular tachycardia because the ventricle is activated first and only here during tachycardia. So it looks like a ventricular tachycardia. Thatís where the activation is coming from, right from the ventricle there. It goes around and around. Of course itís not ventricular tachycardia because it is super-ventricular tachycardia. Itís just the anti-dromic and itís going the other way.

Atrial flutter fibrillation is the one you really need to be aware of because that is the one that is potentially life-threatening. Some people with WPW have a pathway that is exceptionally fast conducting. Most people fortunately donít. They either have a slow conducting pathway or they have a medium fast pathway. But there are a few that have a fast conducting pathway, so if you happen to have atrial flutter fibrillation and you donít have an

Most adults who have paroxysmal tachycardia have AV node reentry. It turns out to be probably around 60% of adults. As opposed to children and adolescents, which is the highest percentage of AV node reentry, itís about 20% of all SVT. In babies this is extraordinarily rare and in fact it is somewhat controversial. There may be even some who believe it never occurs. So it is very rare in the infant and child and becomes a little bit more common as age grows, and there is a controversy also about is this

The first thing we do - and I think most people would agree with this - that if the patient has shock or severe congestive heart failure, and most of the time these are babies because they canít tell you that they have been in tachycardia for a day or two. They come in and they look septic. If they have a heart rate of about 250 to 300 and you canít see P-waves, itís most likely SVT. And the first thing you need to think about is getting them out. Thatís the first thing. And you donít even have time to do too much more other than document what you have and then proceed on. What you need to do is think about getting them out with DC cardioversion. While you are doing that, I think itís worthwhile to use the so-called dive reflex vagotonic maneuver where you ice on their face. There are various different ways to do it, but I have found that the best way is to put a washcloth in ice-cold water. Take it out, wring it just slightly and then put it on the babyís face. Leave it on for 15 seconds and that is nice to induce this dive reflex. Itís successful about 60% of the time. So if itís not then you want to DC cardiovert and you want to

If you donít have congestive heart failure or shock, then you have more time. You can repeat this three or four times, letting the baby rest. You also have more time to start an IV. You donít even have time, and besides that the patient has such bad circulation that you are probably not going to be able to do it and you certainly donít want to waste time to do it if itís in extremis, of course then you can go into the interosseus route. But if you have time then you start an IV and you give IV

Now, for older children, Iím not going to spend much time on because itís basically the same with the exception - notice that IV verapamil is now appearing. IV verapamil was not on the infant and children because there have been deaths with IV verapamil in infants so we donít give it. The deaths are probably related to the calcium metabolism which is different in infants, the myocardial calcium metabolism, compared to the older child and the adolescent. It also can cause apnea without hypotension, so we donít know exactly what the mechanism is there but we donít like to give verapamil to the young child, and you probably

Hereís some examples of what we just gave. This is a patient who had tachycardia. That was not real fast. I canít remember how fast it was, I guess it was about 250 or so. And we put the ice cold washcloth on here and about seven seconds later the tachycardia converted. Notice a couple of things. Notice that the T-wave of the tachycardia has a peaked quality to it. Notice down here that it does not. The T-wave shouldnít change. Then notice what the P-wave looks like in sinus rhythm. So you can infer with pretty strong confidence that that P-wave was in the T-wave. Therefore this patient probably has a concealed accessory pathway. The reason itís concealed is because there is no pre-excitation WPW delta wave here. Then you could

This is an example of a patient who had tachycardia of about 200, almost 300 beats per minute. Again, look at the T-wave. It looks pretty peaky and you might think there might be an accessory pathway there. I donít give 50 micrograms per kilogram anymore because Iíve never been successful. I always start with 100 now, and in this particular instance we were successful in converting it at 150 and in this particular instance we can say that we are definitely right because we have pre-excitation following the tachycardia. Again, emphasizing that you donít see WPW. You canít tell WPW during tachycardia. You can only infer it by where the P-wave is and you think maybe this patient has an accessory pathway. Then in sinus rhythm, then you can tell that WPW and pre-excitation.

This one is the one that I said you always need to be aware of. You always need to think of this when you see it in the emergency room or in your practice. And that is, notice that this is - this is an 18-year-old patient who presented with syncope - first arrhythmia that he had ever had. Notice how irregular it is. Anytime you have irregular rhythm thatís tachycardia you have to think, is there underlying atrial fibrillation going on? Itís by far the most common irregular rhythm that we deal with. Atrial fibrillation. And then the next question is, why is it wide and aberrant? Look how fast it is. Itís faster than 300 beats per minute, if you take one R-R interval. Well the combination of WPW and atrial fibrillation

This is a diagrammatic example of what these pathways look like in a sagittal section. As I said before, the anulus fibrosis is ordinarily electrically silent. Kit bundle is what we used to call these accessory pathways. Occasionally youíll see that term used. We have found that if you really read what Kit wrote decades ago, he really wasnít describing this so we donít use it anymore. But it can occur along the mitral anulus, it can occur over here at the tricuspid anulus. It also can occur right beside the normal AV node and his-bundle in the septal area. So these can be anywhere across the anulus from left to right.

This is an illustration of what we do for ablations when patients have accessory pathway and they come to the catheterization laboratory for a curative procedure. We map by taking a catheter inside the heart and on fluoroscopy as well as intracardiac electrograms, we find where this accessory pathway is by our mapping procedure and we do multiple different ways of determining where it is. When we find it we then turn the RF generator on by focusing in this large tipped catheter, electrode catheter, focusing RF energy and heat it up to about 60 degrees centigrade. This is an actual example here of an electrocardiogram where we turned it on and you can see the delta wave and a very prominent pre-excitation here. The P-R interval is extraordinarily short. This is one second from here to there. So within a second we are successful in ablating thin accessory pathway and the patient does not have any WPW anymore.

But we for sure start those patients on drugs therapy. Then we continue the drug therapy for three to 18 months, depending on a lot of factors. Then we stop it if they have not had any recurrence. If they have continued non-sustained tachycardia, in other words on Holter screening they may not have tachycardia but they have the inclination that we know that if we did stop it itís

Almost always with older children the tachycardia is tolerated very well. So that most of them end up on this side of the algorithm and if a patient comes to me with a first time episode I almost always do not start chronic therapy because I donít know if this is an isolated incidence or if itís going to be some time in five years or ten years, as long as they donít have life-threatening signs or symptoms. If they have life-threatening signs and symptoms and come in like that other patient that I showed you did, they go right to the cath lab because that is a life-threatening problem. Thatís not very many patients, but if they are in this other group then I most of the time do not recommend any treatment. The one thatís the most difficult is the athlete that has WPW and it is either noted incidentally or after one episode and they are minimally symptomatic, but that possibility that they may have atrial flutter fibrillation at some point and have been life-threatening sign or symptoms after that point, is a very difficult and controversial area that we argue about every time we go to meetings as to what to do with him. At one end people are saying or advocating; if itís there we should get rid of it. Well, the risk of the procedure may be higher than having it, having the risk of having the tachycardia episode or atrial fibrillation in the future. The chance of having atrial fib, if you have WPW, is higher than if you didnít have WPW but itís not very high. The risk for adults, we do know that if you take 100 patients with WPW, whatís the chance of them having a life-threatening event in ten years is about one in 100. So itís 1% for ten years. We donít know what it is in children. It may be higher, lower or the same. So when you look at the risk of the procedure versus the risk of having it, it can be a very difficult thing to decide and a lot of times it goes on the family, referring physician and everybody how they feel about one or the other of the options.