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Understanding where to listen for heart sounds anatomically and what those heart sounds correspond to physiologically is very important.
Now, there are 5 main locations we use to auscultate the heart. You can remember them by using the mnemonic APE To Man (A-P-E-T-M). It stands for Aortic, Pulmonic, Erb’s Point, Tricuspid, and Mitral. The Aortic location is in the 2nd intercostal space, right sternal border. Pulmonic is the 2nd intercostal space, left sternal border (just jump straight across the sternum). Erb’s Point is the 3rd intercostal space, left sternal border (just come down one intercostal space). The Tricuspid location is the 4th intercostal space, left sternal border (down one more). Finally, the Mitral location is the 5th intercostal space, midclavicular line (so you come down one intercostal space, and over to the midclavicular line).
These locations allow us to listen to the closing of the 4 valves of the heart. In order to understand the physiology behind what we’re hearing, we have to know which valves close during which phase of the heart beat.
During systole, that’s your S1 sound, the ventricles are pumping blood out of the heart, so that means the aortic and pulmonic valves have to be open. So the valves that are closing during S1 are the Mitral and Tricuspid valves. In these locations you will hear S1 louder than S2. Then, during diastole, or S2, the Aortic and Pulmonic valves close, and the mitral and tricuspid valves open to allow the ventricles to fill. So in these locations you’re gonna hear S2 louder than S1. Now, Erb’s Point is located smack dab between the Aortic and Pulmonic valves, so it’s considered the best place to hear a strong S2.
So why is all of this so important to know? Well the most common application is going to be in the auscultation of murmurs. A murmur is a whooshing sound that replaces the lub or the dub in a patient’s heart sounds. It signifies either regurgitation or stenosis. Regurgitation is when the valve is supposed to be closed, but isn’t closed fully – so it allows some blood to flow backwards. Stenosis is when the valve is supposed to be open, but for whatever reason can’t open all the way – so it causes a turbulent sound as the blood tries to fit through a smaller opening.
So, if you hear a whoosh over the 2nd intercostal space, right sternal border – the first thing you can conclude is that it is an Aortic Murmur. So now we just have to determine if it’s whooshing on the S1 sound (the lub) or the S2 sound (the dub). So is it whoosh-dub…whoosh-dub or is it lub-whoosh…lub-whoosh? Let’s say it’s whooshing on the S2 sound over the Aortic location. Remember what the Aorta is supposed to be doing during S2 (which is diastole)? It is supposed to be closed. So if it’s supposed to be closed, but doesn’t close fully that’s called Regurgitation. So we can conclude that an S2 murmur over the Aortic location is indicative of Aortic Regurgitation.
Let’s do another one. Let’s say I hear an S2 whoosh over the Tricuspid location. What should the Tricuspid valve be doing during S2 or diastole? It should be open, right? So if it’s supposed to be open, but doesn’t open fully, that’s called Stenosis. So we can conclude that the patient may have Tricuspid Stenosis.
Think of regurgitation like a drafty window – when you close it, you expect to keep all the cold air and wind out, right? But if it’s not sealed all the way, it allows some to come back in.
And stenosis is like putting your finger over the end of a garden hose. The smaller hole means the water flows out faster. You can even hear the flow gets louder. It’s that turbulence that you’re hearing in your murmur.
So the 5 locations we listen to heart sounds are Aortic, Pulmonic, Erb’s Point, Tricuspid, and Mitral. Each sound is made by the closing of the 4 valves of the heart. Regurgitation occurs when a valve should be closed but isn’t closed fully. Stenosis occurs when a valve should be open, but can’t open fully.
Now, while you won’t be diagnosing patients or anything like that, it is really important that you can recognize these murmurs. If your patient suddenly develops a new murmur, it could mean something really severe is happening, for example a papillary muscle rupture, so recognize those changes and be sure to notify the provider right away.
You know, I take students to clinical on a Cardiac floor and we had a patient who had severe endocarditis and mitral regurgitation. She was the sweetest thing and she would ask all the students to come listen to her murmur. I would let them listen and then try to tell me what they thought was going on. So when you’re in clinical, and you hear a bit of a whoosh, use the cheat sheet in this lesson or the card in your Scrub Cheats to decipher what’s actually happening in your patient! You’ll be so proud of yourself when you figure it out and then look at their chart and see that you were right!
Now, this is just a bonus – I wanted you guys to be able to see what this looks like in real time. You can’t visualize the aortic valve in this, but you can see the Tricuspid and Mitral valves and the Pulmonic valve. You can see how the heart is like a well oiled machine. Remember the sounds of the heart are from valves closing. The tricuspid and mitral are your lub and the aortic and pulmonic are your dub. So watch this – lub dub .. lub dub. As far as what’s contracting – you’ll notice that the atria contract a split second earlier than the ventricles, that’s your atrial kick – it helps finish filling the ventricles before they contract to push blood out of the heart. You can also see how if the mitral valve wasn’t closed all the way, it may force some blood backwards – that’s regurgitation and that’s what causes a murmur!
I hope this has been so helpful for you to know how to identify the heart sounds anatomically, but also understand what they mean physiologically! That’s exactly what we want for y’all – to have the tools and confidence you need to take care of your patients with excellence!
So go out and be your best self today and, as always, Happy Nursing!