In this video, we are going to talk about the natural pacemakers in the heart. So our heart has this awesome backup system. So we're going to go through each of these pacemakers and the key characteristics of each. So first of all, the SA node or the sinus node, is the heart’s natural pacemaker, and it generates a sinus rhythm. So the inherent rate of a sinus rhythm is between 60 and 100 beats per minute. And key characteristics of a sinus rhythm include P waves that are upright and uniform in appearance, and there will be one P wave for each QRS complex. If the sinus node fails, then the atrial foci will take over and create an atrial rhythm. So the atrial rhythm's inherent rate is between 60 and 80 beats per minute. And key characteristics of an atrial rhythm include abnormal P waves, or instead of P waves, we may get fibrillation or flutter waves instead.
Then if the atrial foci fails, then the junctional foci take over. They're in the AV junction, and they create a junctional rhythm with an inherent rate between 40 and 60 beats per minute, so quite a bit slower. Key characteristics of a junctional rhythm include inverted or absent P waves, P waves that occur after the QRS complex, or PR intervals that are very, very short, abnormally short. And then if the junctional foci fail, then the ventricular foci take over and create a ventricular rhythm. The inherent rate of a ventricular rhythm is very slow, between 20 and 40 beats per minute. And key characteristics of a ventricular rhythm include no P waves and abnormally wide QRS complexes. So when we were doing our QRS complex on the last video, if you recall, the QRS complexes were very wide and there were no P waves, so we know, right off the bat, that we're looking at a ventricular rhythm.
So all the information I just went over can be found on card 13 in my deck. It's really important to be able to differentiate a sinus rhythm from an atrial rhythm from a junctional rhythm from a ventricular rhythm. And so if you know the key characteristics of each, it will be easier to do that. So in my next video, we will start getting into sinus rhythms, which again are created because of that SA node or sinus node. So stay tuned, and I look forward to helping you understand how to differentiate these rhythms. Take care!
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