 So this video, it will talk about Wolff-Parkinson-White syndrome. In the normal heart, impulses go from the essay note, through the AV note, down to the ventricles. In Wolff-Parkinson-White syndrome, there is an accessory pathway. Most of these pathways will allow impulses to either go up or down through it. There are three main scenarios in which we need to consider the effect of Wolff-Parkinson-White syndrome. These three are in sinus rhythm. We entry tachycardia and atrial fibrillation. We'll take it through one by one. The first scenario is a sinus rhythm. In a normal heart, impulses go from the essay note down to the AV note. There's a slight pause and then the ventricles depolarize. In the patient with an accessory pathway, the impulses travel from the sinus note to the AV note. It also travels from the sinus note through the accessory pathway. The accessory pathway does not have that stopping that the AV note does, so there's no pause. And therefore the ventricles depolarizes through the accessory pathway just a little bit faster than the normal pathway. And since it does not go through the normal conduction pathway, the QRS complex will be wide. This is what it would look like on an ECG. Here is the essay note. It reaches the accessory pathway. Depolarizes the ventricles earlier and wider. Since there are two different ways to depolarize the ventricles, this is what the result ECG would look like. You have your essay note, and the ventricle depolarizes first through the accessory pathway first, and then the regular depolarizing catch up. What you see is this earlier depolarization, which is really captured by this. This is the delta wave. And you can also see that the resultant QRS complex is wide. The second scenario we want to look at are reentry circuits. In particular, we want to look at AVRT, atrial ventricular reentry tachycardia. The accessory pathway forms a loop in which it allows for circular movement of the impulses. It comes in two different forms. The much more common form involves the impulses coming down from the essay note through the AV note, goes up the accessory pathway and goes through the AV note again, forming a circuit. This, which is the much more common form, is called an orthodromic conduction. The other much less common form, as you can imagine, involves the essay note having an impulse going down to the AV note. But instead of going through the AV note, the circuit goes through the accessory pathway this way, and goes up the AV note, forming that kind of circuit that is called anti-dromic conduction. We'll talk about them one by one. Let's start with orthodromic conduction. In orthodromic conduction, impulses are still traveling down the AV note in the correct way and therefore reaching the bundle branches in the correct way. The rate is fast since the impulses travel quickly between the AV note and the accessory pathway. What about the cure as complexes? Are they regular? Yes, they should be regular. What about whether they are wide or narrow? Well, since the impulses are going down the AV note the normal way, the complexes should be narrow unless there is a pre-existing bundle branch block. This is what the ECG should look like. Does it fulfill the criteria we talk about? The rate is fast. The complexes are regular. They are also narrow. In terms of treatment, all we have to do is to block this crazy circuit that's going around the AV note through the accessory pathway. We do this by vagal maneuver or blocking the AV note. That resets the circuit. Then impulses should be traveling from the SE note directly down to the AV note and traveling through the circuit again. Since the accessory pathway still exists the impulses will still also go through the accessory pathway causing that delta wave that we see earlier. What about the second less common form of the re-entry circuit? The entry-dromic conduction. This is when the accessory pathway allows the conduction through it the normal way and then go up through the AV note. Based on what you know what do you think the ECG would look like? Well the rate will still be fast since there is still a circuit going around and around. It would also be regular. Now is it going to be narrow or wide? Well since the accessory pathway doesn't follow the regular conduction pathway it is going to create a wide care as complex. We saw this even when it's in sinus. This is important. And let's see what an ECG would look like. This is what an ECG would look like. It's fast, regular, and wide. The problem is that another very potentially bad rhythm also can look like this. A fast, wide, and regular rhythm that would be ventricular tachycardia. Without knowing exactly whether the patient has both Parkinson white or not this has to be resumed to be ventricular tachycardia. Therefore in terms of treatment we want to presume that this is VTAC first. We'll go through a regular ACLS algorithm deciding whether the patient is stable or unstable. And ultimately we'll end up using probably electrical cardioversion. That is the safest approach. Since electrical cardioversion will also work to reset this loop. What if we're really sure this is antidromic conduction since the patient has a history that's the way they've always presented. We can use medications first but we have to be very careful not to block the AV node. Since you're trying to re-establish a circuit that goes from the ASA node down to the AV node and through the AV node into your regular conduction pathway. What you want to do is to block the ASSESRI pathway conduction and you have to do this selectively. To block this you can use medications such as procanomide or amiodarone. But electrical cardioversion also works. But please bear in mind and I'll say it again. This looks just like ventricular tachycardia and therefore unless we are extremely sure this is what it is we should just treat it as such. It's helpful for us since the treatment for ventricular tachycardia is basically identical to what we just proposed here. So to summarize what we have so far we have Wolf-Barkinson-White syndrome in Sinus rhythm which simply shows us the delta wave we have it in a reentry circuit much more often in the orthodromic version versus the antidromic version. In orthodromic version would be narrow, regular, fast and antidromic will be wide, regular and fast. In orthodromic block the AV node in antidromic treat as VTAC. And you will be able to tell that this is orthodromic because the complexes are narrow versus wide. Once we are clear with this let's move on to the third one which is when there is atrial fibrillation. In atrial fibrillation with Wolf-Barkinson-White syndrome there are two problems. First there is atrial fibrillation. Fast rhythms are being generated from the atrium. Some of it is going through the AV node and down the regular pathway. Some of it is going down the accessory pathway. The first problem is that these impulses are fast. There are about 300. For the impulses that's going through the AV node since the AV node will stop and pause these impulses it will not be conducting at 300. The problem is that there is no such pausing mechanism as we discuss in the accessory pathway. It will conduct whatever it sees from the atrium. This together with the fact that the accessory pathway does not block causes the patient to degenerate into VF or VTAC. This is the most dangerous of patients with Wolf-Barkinson-White syndrome. What would the ECG look like? Since the rhythm underlying is a fib it is irregular. Since a lot of the impulses are going down the accessory pathway it is also going to be wide. And therefore it would be fast, irregular and wide. This is what an ECG would look like. Does that fulfill our criteria? It certainly is fast. It is irregular and most of the complexes are wide. Those will be the complexes that's going through the accessory pathway. You can still see a few narrow ones if they manage to go through the normal pathway. In terms of treatment of patients with atrial fibrillation and Wolf-Barkinson-White syndrome the best way is to fix the underlying rhythm which is the a fib. The most conservative method will be using cardioversion. This will be the quickest and the most reliable way to convert the patient from a fib back to sinus. This is also the scenario that you do not want to block the AB node because you want to have at least some normal conduction going down the normal pathway. So let's add this to our summary. The third type where we saw was a fib which is a bad, bad rhythm in the patient with Wolf-Barkinson-White syndrome. Wide, irregular and in terms of treatment definitely do not block the AB node. The safest way is to get the patient out of a fib by electricity. I hope this answers your questions. Thank you for watching.