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New Treatments for Arrhythmias in Children

This is a general outline of the approach to arrhythmias. The first thing you are going to do is; what is the heart rate? Fast, slow irregular heartbeat, palpitations? The next thing you will notice is; is it wide or narrow QRS, because obviously you will be worried about how dangerous this might be. And then you will probably start to look a little more closely and see if you see P waves. And the P waves are whatís going to really give you a diagnosis. They can be absent, they can be normal, they might be retrograde or they might be intermittent or multiple. Whenever possible, itís very helpful to

So weíll start with fast heart rates. The most common fast heart rate is sinus tachycardia, as you might imagine. It usually is a heart rate less than 220. The QRS should be normal. That is, the normal QRS for the patient if theyíve had heart surgery or bundle branch block for other reasons, then it might be wide. If you have a 12-lead EKG of their normal rhythm or

The treatment for this is to identify the underlying cause and treat that. If you are unsure if itís sinus rhythm or not, then adenosine can often be diagnostic. What happens with adenosine is sinus rhythm will slow transiently, you should maintain a normal P wave, which you might be able to see if it comes out of a T wave, and then it should speed back up also very slowly. You

The next most common fast heart rate is supraventricular tachycardia. This is usually an unvarying rate. It will be fixed. It wonít respond to pain and when the child is active and alert it will be the same rate as when the child is asleep. Itís usually a narrow QRS but may exhibit aberrant conduction, left or right bundle branch block and then be wide. P waves can be

One of the more common causes of supraventricular tachycardia and a frequent question on the Boards is Wolff-Parkinson-White syndrome. This syndrome consists of a short P-R interval, a widened QRS, a delta wave which is a slurred up-stroking of the QRS, or in some leads a

Certain children, particularly about 8 to 12-year-old boys, love standing on their head. They can do that. It doesnít work very well in the middle of class. They have often been sent to the 

Atrial flutter, which is also now called atrial muscle reentry, to differentiate it from reentry through the usual isthmus around the tricuspid valve annulus. Atrial muscle reentry is used for patients who have had congenital heart disease and have scars in other places in their atrium where a signal can travel in a circle. These patients usually have atrial rates of 300-500 with 2:1 or higher AV block and ventricular responses of 150-250. These can be very variable, as

Next tachycardia is ventricular tachycardia. This also usually has a steady rate, a wide abnormal-looking QRS. Itís best to check several leads because it can look normal and some leads are narrow. P waves are usually absent or intermittent. An important diagnostic tool is that 

Next weíll go on to slow heart rates. Again, sinus rhythm is the most common slow heart rate; sinus bradycardia. It can be related to increased parasympathetic tone like what you would see with athletes, or anesthesia or sedation. It can also be part of Cushingís triad; increased intracranial pressure which includes hypertension and an obtunded state. It can be seen with hypoxemia. Everybody has probably seen a neonate with apnea and bradycardia. The treatment of sinus bradycardia is to treat the underlying cause as long as itís pathologic. You donít necessarily need to treat an athlete for sinus bradycardia if itís related to their training.

Sick sinus syndrome is the next most common cause of bradycardia. It usually, in children, will follow some kind of surgery or be associated with congenital heart defect. Most commonly, atrial surgery like ASD closure, setting procedures. For patients with atrial septal defect, they can develop sick sinus syndrome without even having had surgery for their defect. Thatís because their defect can involve the sinus node and give them an abnormal sinus node. Itís usually associated with junctional or ventricular escape rhythm and the treatment is; you treat with permanent pacing. There are no drugs that will reliably raise your sinus rate.

Next most common is heart block. First degree heart block does not cause bradycardia because all P waves are conducted, but with a prolonged P-R interval. Each P wave is conducted and the P-R interval is stable. Itís just in excess of whatís normal for age. In general, greater than 200 milliseconds is always abnormal and in most patients greater than 180 milliseconds will be abnormal. There are two kinds of second degree heart block; intermittent failure of AV conduction. The first kind, which is usually benign, is called Wenckebach or Mobitz type I heart block. In this kind of heart block the P-R interval progressively lengthens and then blocks and