Paramedics Course – Normal Sinus Rhythms

Normal Sinus Rhythms

Micro-lecture by the Australian Paramedical College


In today’s micro-lecture, Australian Paramedical College Hon. Snr. Lecturer Sam Willis talks about how to manage the normal sinus rhythms.

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Normal Sinus Rhythms

Today we are going to talk about normal sinus rhythms. Now to answer this question is to talk a little bit about normal sinus rhythms. We need to go back to the basics of the electrical conduction system within the heart. Now here you can see a typical picture of a heart, with the electrical conduction system in yellow.

Now this sinus node, in the top left-hand corner, or actually the right wall of the atria, is where the electrical conduction system starts. Now, the sinoatrial node or the sinus node is responsible for generating that first impulse and sending it down to the next stage, called the atrioventricular node. The AV node then pushes it down the rest of the pathway, including the bundle of His, the left bundle branch, and the right bundle branch, and then into the Purkinje fibers.

So really it starts with this sinus node, which is a collection of highly specialised cells, all clustered together. Now the sinus node is also called the pacemaker. Now when you look at a normal ECG, and I have one here ready to show you guys, you’ll notice how the ECG is made up of a P wave, a Q, R, S wave, and a T wave.

So that is what we call a normal sinus rhythm. Now it’s called normal because of the rate, usually between 60 to 80 beats per minutes at rest, and it’s called sinus because it has a P wave. The P wave represents atrial depolarization. So let’s talk about atrial depolarization.

So the sinus node fires its electrical impulse and it moves down here towards the AV node, but it doesn’t just move in a straight line. It also moves across both atria. As a result of the electrical activity moving across the atria down to the SA ventricular node, the atria contracts. Now as it does so, you have a P wave on the ECG, as you’ve just seen.

So the good news is that there’s a P wave on the ECG, which means that the atria are contracting and it’s starting at the sinoatrial node, which is exactly what it should be doing. Now whenever you have a rhythm that has a P wave, it’s always called sinus rhythm.

So let’s say for example you had a rhythm that was 110 beats per minute, but there was a P wave, that’s called sinus tachycardia. Let’s say that you had a rate of 40 beats per minute, but there was a P wave. That’s called sinus bradycardia. And just to summarize, it’s called sinus because the sinoatrial node is doing its job, it’s firing. As a result, the atria are contracting and you end up with a P wave on the ECG.

So I hope you’ve enjoyed this micro-lecture on sinus rhythms.

For more information about courses and becoming a Medic / Paramedic or any other professional in the pre-hospital emergency health care sector Contact the Australian Paramedical College today:

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