 Hi and welcome to Nursing School Explained. This video is the first video of a series about atrial rhythms and will go into the specifics about premature atrial contractions, also known as PACs. If you haven't already done so, I highly recommend that you watch my other videos about basic electrophysiology as well as EKG interpretation basics where I explain on how to use the EKG paper and determine the heart rate as well as the other video on basic EKG interpretation where I'll discuss the normal intervals and rules to memorize that you can apply to every single dysrhythmia. So let's look at premature atrial contractions. So whenever there's atrial in the word, that means that the impulse originates in the atria. Pretty self-explanatory here. And remember that the atrial depolarization and contraction is represented by the P wave and that is usually upright. And in any kind of atrial dysrhythmia, that means that the impulse originates from any location in the atria other than the SA node. In my other video about the principles of electrophysiology, I discuss the properties of cardiac pacemaker cells including automaticity and excitability or irritability. And this applies here as any cardiac cell can initiate an impulse. So now when we're talking about a premature atrial contraction, it means that we have an irritable cell somewhere in the atria that discharges before the regular SA impulse comes through. And because this atrial contraction is premature, it still depolarizes the atrium and therefore causes a ventricular depolarization, which is the QRS complex. Now looking at the rules for PACs, the rate will always depend on the underlying rhythm. Mostly it will be normal, like a 60 to 100 beats per minute. But the rhythm, because the PAC occurs early in the cardiac cycle, will be irregular. So the PAC initiates this early beat. Still principle number three, P waves will be upright and one for every QRS. But here in red, you can see I highlighted that the PAC occurs early or prematurely in the cardiac cycle. And then principle number four or rule number four goes into the intervals. So the PRI in PACs will be normal for the normal beat, as well as for the early beat. And the QRS will be normal as well, less than 0.12 seconds. So this example down here at this rhythm strip, we can look at first the rate. So we'll look at one, two, three, four, five, six, seven, eight, nine, 10 QRSs, which will give us the heart rate of 100. And then we can already see that this is pretty irregular here. Even without looking with calipers or looking at that EKG paper, we can see that the distance between these two beats is longer than, let's say, between this one and this one. And the arrows here on this rhythm strip up on top signify the early beats or the PACs. So every other beat on this rhythm strip, there is a premature atrial contraction. And so I can see that it's irregular. So we've checked rate, we've checked rhythm. Now the P waves are upright here, upright, upright, upright. This one is kind of almost like merged into the T wave from the previous complex, upright P here, upright P here, upright P. So they all march out. And there's one for every QRS, which matches as well. But then we have these early beats. And sometimes because the irritable focus does not come, well, the impulse does not come from the SA node, but for a different location, the P wave will be shaped a little bit differently. So if we compare this P wave here, for example, it's a nicely looking regular P wave, where, for example, this one over here has kind of like a little notch in it, which could be that it's kind of hidden, that there is the T from the previous complex and then the P right here. But it certainly looks different from the other regular beats. And so this is this PAC that we're talking about here that occurs early in the cardiac cycle. And then we can look at our intervals here again. And that should be the same whether or not we look at the early beat or the regular beat basically. So let's find one that we can easily count. So let's find this third beat right here. We have one, two, three, four boxes from the PRI, which is 0.16, which will make the PRI normal. And then a QRS that's easy to look at. We could maybe look at this one right here. So the QRS again starts here at this thicker line and then goes into one two. So that's two boxes. So 0.12. So that's a normal QRS. So the only thing that's abnormal here is that the rhythm is irregular and that we have this differently shaped P wave and that it occurs early knowing we know this by this irregular rhythm here. Here's another look at this rhythm strip a little bit bigger and you can see they also point out that the R2R is longer here. So this is when we're looking at the regularity with the calipers or the EKG paper marching that I go over in my other video. But you can basically with the naked eye already see that these differences or these beats occur at different intervals and are irregular. Causes of PACs might be emotional stress, congestive heart failure, myocardial ischemia or injury that cause the cells in the atria to be excitable or irritable. Fatigue can lead to PACs. Digoxin toxicity. Remember digoxin has a very narrow therapeutic range and if it goes out of range it can cause dysrhythmias and PAC would be one of those. Hyperthyroidism. So anything that makes the myocardium more excitable again in hyperthyroidism the activity goes up everything will be faster so it also can cause irritability in the cardiac cells. Hypokalemia as well as hypomagnesemia can cause PACs and then excessive intake of caffeine, tobacco and alcohol so careful with your caffeine intake and any kind of energy drinks that you might consume while you're in nursing school. Signs and symptoms. Patient may be asymptomatic because it's a very benign beat but they might have the sensation of palpitations or a skipped beat. Treatment for PACs. There is basically none needed if the patient is asymptomatic or these PACs occur very infrequently. However, PACs mean that there is an irritable focus sitting in the atria and that might get more irritable over time so let's say this is due to hypokalemia or hypomagnesemia. If that underlying cause is not treated it might initiate other atrial dysrhythmia such as atrial fibrillation, atrial flutter or supraventricular tachycardia that I'll be discussing in a different video and so then the treatment always is treating the underlying cause whatever that might be. Here are some references. I always refer to practical clinical skills so you can practice your rhythm strips and they also have some pretty good descriptions and life in the fasting as well as as well as medic tests they have some great resources for EKG interpretation as well. Here are my other videos. The other atrial rhythms that I'll be discussing is atrial fibrillation, atrial flutter and supraventricular tachycardia here in this atrial rhythm series. Please subscribe to my channel if you enjoy these videos leave me comments below and I'll see you soon. Thanks for watching Nursing School Explained.