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Video transcript

atrial flutter is one of the harder rhythm is that's also known as just flutter it's one of the super ventricular tachycardias now remember that the heart's dominant pacemaker is the SA node and the SA node is going to send a signal to the AV node which will then conduct a signal down to the lower half of the heart which makes the ventricles contract in case the SA node fails the heart has several backup pacemakers called automaticity foci these backup Pacers only fire in the event that the signal from the SA node is not efficiently or effectively reaching the AV node and when they do fire they fire at a rate between 60 and 80 beats per minute or bpm an atrial flutter there's a really irritable automaticity focus and I'm drawing that here in purple this irritable focus is going to fire at array between 250 and 300 beats per minute which is a lot faster than rest of the foci the electrical signal travels around in a circular pattern loose around again and again and again and again and again so this causes the atria to contract at a rate between 250 and 300 beats per minute every time the signal goes around is going to hit the AV node and remember the AV node is what conducts the signal down to the lower half of the heart and makes the ventricles contract so you might think because of that the ventricles are also going to contract at a rate between 250 and 300 beats per minute but in reality the ventricle is used to contract at a slower rate around 150 beats per minute now why is that that's because there's a built-in mechanism in the AV node called a refractory period other tissues have this too after the AV node conducts a signal to the lower half of the heart there's a window of time also known as the refractory period where the AV node can't fire again even if it's a signal do so so this is sort of like a backup mechanism to prevent the AV node from over firing which will then prevent the ventricles from contracting too quickly so let's look at this in EKG with an atrial flutter EKG you're going to see multiple P waves and regular space QRS intervals by regular I mean that the space from this r2 our interval is going to be the same as this r2 our interval which is the same as this art our interval now why do we have these multiple P waves remember that there's an irritable Ottoman to see focus that's over firing who's going to fire fire fire but it won't conduct signal through the AV node every time it fires because of the refractory period so for example here we have the focus firing causing the atria to contract a hits AV node conducts makes a QRS complex and it tries to fire again but because we're in the refractory period it's not going to conduct through the AV node and you're not going to get another QRS complex instead you're going to see another P wave when it tries to fire again in this particular example we have three P waves for every QRS so this is called three two one conduction in a trio folder you can also have two to one conduction where you'd have two P waves for every QRS or even four or five P waves for every QRS but this example is three to one conduction and if you look closely you can appreciate that the lines that the P waves may make a certain pattern and they kind of resemble the teeth on a saw so classic a flutter is said to have a saw tooth pattern and the Sawtooth are the p-waves