 Hey everybody, Dr. O here. In this short video I'm going to cover just the basics of the EKG. This is not a cardiology class. We can teach an entire class just on how to interpret EKGs, but I'm just going to introduce the topic to you. So an EKG is a measure of the electrical activity of the heart. If you see a problem on EKG, that's going to be called an arrhythmia. And again, a cardiologist will be able to tell you what kind of issue someone's having, but we're just looking at a normal EKG and then hopefully you can get a sense when something isn't right. So here's all the key stuff I'm going to ask you to know is looking here, you see the common, you know, typically looking EKG on the left hand side. We have the P wave, the QRS complex and the T wave. And these are going to be the three things I ask you to know. The P wave is what occurs during atrial depolarization. So that's going to happen right before the atria contracts. So the P wave is measuring when the atrial cells are depolarizing. The QRS complex is a measurement of ventricular depolarization. So the QRS complex is going to happen right before your two ventricles contract. The T wave is a measure of ventricular repolarization. So when the ventricular cells are repolarizing so they can go ahead and get ready to fire again. So notice what's absent here. You do not, you cannot see atrial repolarization. And the reason that you can't see it is because it's happening during that QRS complex. It's happening underneath the QRS complex when the ventricles are depolarizing. So P wave, atrial repolarization, QRS complex, ventricular depolarization, T wave, ventricular repolarization. So don't worry about like PR segments, ST segments, those are super important if you're trying to diagnose something using an EKG. But I just need to know the basics of what's happening with a normal EKG. So you'll notice the boxes. So when you actually like in lab, if we're measuring, doing measurements on an EKG, let me show you what a box means. So an individual box is going to be 0.04 seconds of time. So that 0.2 seconds as they block there are five blocks. So an individual square on an EKG strip is going to be 0.04 seconds horizontally. Vertically, an individual box is going to be 0.1 millivolts. So you're measuring voltage by counting up or down, you're measuring time left and right. All right, just to review and I want to connect the EKG to the conductance system of the heart because that's what we're measuring. We've already covered that but here you see on the left, when the SA node fires its action potential and depolarizes the atria, that's going to show up as the P wave, that little space there. After the P wave, that's the 100 millisecond delay. Once we get to the AV node or atrial ventricular node, then we have the, when the bundle branches and the bundle of his and the bundle branches and the brachinjee fibers contract, that's going to be your QRS complex. And then right after that, the ventricles would contract and then the whole process would happen again. Okay, so that is how to look at an EKG and why it matters. I hope this helps. Have a wonderful day. Be blessed.