hey everyone it's sarah with registerednessrn.com and in this video i'm going to be reviewing the parts of the ecg waveform so let's get started so first let's look at the p wave the p wave represents atrial depolarization so this leads to the contraction of the atria which is created by the sa node so whenever those atria contract it creates this little wave now right after the p wave and before the qrs complex we can find the pr segment and the pr segment demonstrates the delay the av node created remember it was the gatekeeper so it gave the atria time to dump its blood into the ventricles before the ventricles contracted also found in this area is the pr interval and i really want you to remember the pr interval because we measure this and it's very important in determining if your patient has a heart block so the pr interval starts at the beginning of the p wave and extends to the beginning of the qrs complex so it's different than the pr segment the pr segment was after the p wave the pr interval is before the p wave to the beginning of the qrs complex and this demonstrates the amount of time it takes for the electrical signal to go from the atria to the av node and if it's taking too long if we have a long pr interval this could indicate a heart block next is the qrs interval or also known as the qrs complex and this represents ventricular depolarization so this is leading to the contraction of the ventricles also found in this but you can't see it is atrial repolarization where the atria are relaxing but the ventricles are so large that whenever the atria relax it's overshadowed by the ventricles so you're really only seeing ventricle depolarization here then we have the j point and this is the point where the qrs complex meets the st segment and the st segment represents the completion of ventricular depolarization and the beginning of ventricular repolarization and this segment should be flat hence it should be isoelectric meaning flat so there should be no depression of it or elevation and isoelectric is a word that is used to describe straight across lines of the pqrst complex that represents that the heart cells are resting they're not contracting and causing electrical activity so nones being transmitted to the ekg then here we have the t wave the t wave represents the beginning of ventricular repolarization so relaxation and the ventricles are so big that whenever they relax it creates this t wave and then after the t wave you usually have a flat line which is representing ventricular repolarization is complete it's a flat line isoelectric and then the cycle starts immediately again where you get a new p wave qrs complex t wave and it just keeps going on now sometimes after the t wave you may see a u wave it's not the case in a lot of patients but in some patients and it may be happening because your patient's potassium levels low like in hypokalemia and then lastly here is the qt interval the qt interval starts at the beginning of the qrs complex and ends after the t wave and this demonstrates the time it takes for electrical signals to cause the ventricles to contract and then rest so now let's recap all that information and look at this pqrst complex and see how depolarization and repolarization is occurring in each part of that complex so here section one is the p wave that represents atrial depolarization beginning so we have the contraction of the atria then two that was our pr segment that was atrial depolarization complete so it's done then three was our qrs complex and it represented ventricular depolarization beginning and in there but you can't really see it is atrial repolarization it's relaxing then four is our st segment and that is ventricular depolarization completing then we have five which represented our t wave and that is ventricular repolarization beginning and then six is that flat isoelectric line and this is ventricular repolarization complete okay so that wraps up this video and if you'd like to watch more videos on ecg interpretation you can access the link in the youtube description below