Hi this is Tom from Zero2Finals.com. In this video I'm going to be going through heart murmurs. You can find written notes on this topic at Zero2Finals.com or in the cardiology section of the Zero2Finals Medicine book. Let's jump straight in. First of all we need to talk about the normal heart sounds and we refer to these as S1 and S2.
The first heart sound, or S1, is caused by the closing of the atrioventricular valves. Now this is the tricuspid and the mitral valve. And this happens at the start of systolic contraction of the ventricles.
So as the ventricles try to push blood out of the heart, the valves between the atria and the ventricles need to close to prevent blood from flowing back into the atria. The second heart sound, or S2, is caused by the closing of the semilunar valves, and this is the pulmonary and the aortic valves, once the systolic contraction is complete. And this is to prevent blood flowing back from the pulmonary arteries, or the aorta, into the ventricles.
Now this S1 and S2 can be heard during auscultation of the heart sounds as a lub-dub sound. So let's have a listen to that now. Next let's move on to a third heart sound and we call this S3 and this is heard roughly 0.1 seconds after the second heart sound. It's quite subtle So you can only just about hear an extra sound after the second heart sound. Let's listen to an example Now what causes this sound is, I think of it as rapid ventricular filling, causing the caudate tendini, or the tendons inside the heart, to pull to their full length and twang like a guitar string.
This can be normal in young patients, you know 15-40 years old, because the heart functions so well that the ventricles easily and rapidly fill with blood, but in older patients it indicate heart failure as the ventricles and the chordae are stiff and weak so they reach their limit much quicker than normal. So the way I picture this is you know an older patient bending over and their tight hamstrings very quickly and sharply tightening as they reach the limit of their flexibility. This often sounds a bit like lub-du-dub, lub-du-dub.
So let's have a listen again to what that sounds like and see whether you can distinguish. a third heart sound after the second heart sound. Next, let's talk about the fourth heart sound, and we call this S4. And this is heard directly before S1.
And S4 is always abnormal, and it's relatively rare to hear. What this indicates is a really stiff or hypertrophic ventricle and the sound is caused by turbulent flow from an atria that's contracting against a ventricle that is non-compliant or doesn't want to fill with blood. So the ventricle is really stiff, the atria is trying to force blood in and this is causing a turbulent flow. And what it sounds like is lulubdub.
So let's have a listen and see if you can distinguish that fourth heart sound just before the first one. Now let's talk about heart murmurs. So when you're listening to murmurs, you want to auscultate with the bell of your stethoscope to hear low-pitched sounds and the diaphragm of your stethoscope to hear high-pitched sounds.
And you can think of this as a child's high-pitched scream from their diaphragm, or a church bell giving a deep bong. You want to listen over the four different valve areas in term for murmurs. So the pulmonary area is at the second intercostal space on the left sternal border.
The aortic area is on the second intercostal space on the right sternal border. The tricuspid area is in the fifth intercostal space on the left sternal border. And the mitral area is in the fifth intercostal space in the midclavicular line.
And this is the apex area. You can also listen at what's called Erb's point and this is the third intercostal space on the left sternal border and this is the best place for listening to the heart sound, so S1, S2, S3 and S4. There's a couple of special manoeuvres you can use to look extra clever in your OSCEs.
This would be to put the patient on the left hand side or roll them over onto their left hand side to listen to mitral stenosis. Or you can sit the patient up, lean them forward and ask them to take a deep breath out and hold and this helps you to hear aortic regurgitation. There's a few features of a murmur that you can assess and we use a mnemonic called script.
So S is for sight meaning where is the murmur loudest. C is for character so is it soft, blowing, crescendo meaning getting louder, decrescendo meaning getting quieter. or crescendo-de-crescendo, meaning getting louder and then quieter. R is for radiation, so can you hear this murmur going to the carotids, as you would in aortic stenosis, or going to the left axilla, as you would in mitral regurgitation? I is for intensity, so what grade is the murmur?
P is for pitch, is it high-pitched or is it low and grumbling? and pitch basically indicates the velocity of the murmur. And then finally T is for timing, so is it systolic or diastolic.
So I'll go through that mnemonic again. Script, meaning sight, character, radiation, intensity, pitch and timing. Let's talk about the grade of murmurs.
So grading a murmur is quite subjective. But it can be helpful in assessing the severity of the defect and it will also make you sound clever when you grade a murmur in your OSCEs. If in doubt, it's probably grade 2 or 3. So grade 1 is difficult to hear. Grade 2 is quiet.
Grade 3 is easy to hear. Grade 4 is easy to hear and with a palpable thrill. So when you put your hand on the chest you can feel the murmur.
Grade 5 is when you can hear the murmur with your stethoscope barely touching their chest. And grade 6 is when you can hear the murmur with your stethoscope actually off to the chest, just holding it nearby. Let's talk about hypertrophy and dilatation of the heart.
Valvular heart disease can cause hypertrophy, which is where the heart muscle thickens outwards and into the chamber of the heart. or it can lead to dilatation, which is where the heart muscle gets thinner and expands. Think of it blowing up like a balloon.
And this happens in different heart areas depending on where the pathology is. When the heart muscle is pushing against a stenotic valve, it has to work a lot harder to try to get the blood to go through that valve. So this results in hypertrophy. So if you have mitral stenosis, the left atrium is pushing really hard against that mitral valve. So you get left atrial hypertrophy.
When you have aortic stenosis, that left ventricle is pushing really hard against that aortic valve. So you end up with left ventricular hypertrophy. When you have a leaky valve that allows blood to flow back into the chamber, it stretches the muscle and results in dilatation. So when you have mitral regurgitation, there's blood flowing back through the mitral valve.
into the left atrium, so you end up with left atrial dilatation. When you have aortic regurgitation, there's blood flowing back from the aorta into the left ventricle, so you end up with left ventricular dilatation. Let's talk about our first murmur.
So we'll start with mitral stenosis, and this is where the mitral valve becomes narrowed and makes it difficult for the left atrium to push blood through to the ventricle. It's caused by two things, rheumatic heart disease and infective endocarditis, and it causes a mid-diastolic, low-pitched rumbling murmur due to the low velocity of the blood flow. Because the blood is flowing through such a narrow area, it flows only very slowly and rumbles its way through. You also get a loud S1 due to the thick valves that require a large systolic force to shut. Once the systolic force reaches a certain threshold, the valve shuts very suddenly.
So what you end up with is this loud lub and then a dub dur. So let's have a listen to it. So did you catch that loud first heart sound and then that second heart sound followed by that rumbling murmur?
Let's have one more listen. A few other features of mitral stenosis is that you'll be able to palpate a tapping apex beat. due to the loud S1, and it's also associated with a malar flush. This is a flushing of the patient's cheeks due to back pressure of blood into the pulmonary system, causing a rise in CO2 and vasodilation.
It's also quite commonly associated with atrial fibrillation, and this is due to the left atrium struggling to push blood through a stenotic valve and causing disruption to the electrical signals. resulting fibrillation of the atria. The next murmur to talk about is mitral regurgitation. Mitral regurgitation is when an incompetent mitral valve allows blood to flow back through during systolic contraction of the left ventricle.
Because during systole there's blood flowing backwards through this valve you end up with something called a pan-systolic murmur meaning the murmur is present throughout the systolic period. and it causes a high-pitched whistling murmur due to the high velocity of blood flow through the leaky valve. This murmur sounds a bit like brrr, brrr, because it happens the entire way through systole.
Let's have a listen. You can hear that the murmur is present throughout the whole of systole between S1 and S2. And this is what we call a pansystolic murmur.
Let's have a listen one more time. When you hear this murmur, listen at the axilla, because it tends to radiate to the left axilla. It's also associated with congestive cardiac failure.
because the leaking valve causes a reduced ejection fraction and causes a backlog of blood that is waiting to pass through the left side of the heart. Therefore, you might also hear a third heart sound when listening to this murmur if there's heart failure present. So what causes mitral regurgitation?
Well, the most common cause is idiopathic weakening of the valve with age. So as a patient ages, their valve just naturally gets a bit weaker. It can also be associated with ischemic heart disease, infective endocarditis, rheumatic heart disease, or connective tissue disorders such as Ehlers-Danlos syndrome or Marfan syndrome. Next let's talk about aortic stenosis. So aortic stenosis is probably the most common valve disease that you'll encounter.
It essentially means a narrow aortic valve and so As blood flows through this narrow aortic valve during systolic contraction, there will be turbulence of blood flow. So this causes an ejection systolic murmur, and this is a murmur that occurs while blood is being ejected from the left ventricle. And it's a high-pitched murmur because of the high velocity of systolic contraction.
It's also what we call a crescendo-de-crescendo murmur. as it gets louder and then quieter due to the speed of blood flow during the different times of systolic contraction. So you'll hear the first heart sound and the second heart sound, and then between those heart sounds, you'll hear a systolic murmur that gets louder and then quieter.
It causes a murmur that sounds a bit like burr-dub. See if you can hear it. There's a few other signs that you'll find in a patient with aortic stenosis.
The murmur will radiate up to the carotids as the turbulence continues up into the neck. So you can put your stethoscope over the carotid arteries and listen for a murmur there. It's also associated with a slow rising pulse and a narrow pulse pressure.
So when you palpate the pulse, it'll be slow to rise, and when you do the blood pressure, the systolic and diastolic pressure will be quite close to each other. Patients with aortic stenosis also have symptoms of exertional syncope. This is lightheadedness and fainting when exercising, and this is due to difficulty maintaining good flow of blood to the brain through that narrow valve. The most common cause of aortic stenosis is just idiopathic age-related calcification of that valve. It's just the valve becoming older with age and calcifying, becoming hardened and narrowed.
It can also be caused by rheumatic heart disease. The final murmur that we're going to talk about is aortic regurgitation. Aortic regurgitation is basically where the aortic valve becomes incompetent and blood is able to flow back from the aorta and into the left ventricle.
Because blood flow back through this valve will happen during diastole, aortic regurgitation causes an early diastolic and quite a soft murmur. So it sounds a bit like lub-tar. See if you can hear it on this example. Don't worry if you can't hear it, it's a really subtle murmur that even cardiologists can miss. So have another listen, just see if you can hear it after the second heart sound, a gentle, soft, early diastolic murmur.
Aortic regurgitation is associated with something called Corrigan's pulse. And a Corrigan's pulse, which is also called a collapsing pulse, is when it rapidly appears and then disappears as the blood is pumped out of the ventricles and then immediately starts flowing back through the aortic valve into the ventricles. Aortic regurgitation often results in heart failure and this is due to the back pressure of blood waiting to get through the left hand side of the heart.
It can also cause something called an Austin-Flint murmur, and this is worth knowing about just for your exams. It's heard at the apex and is an early diastolic rumbling murmur. And this is caused by blood flowing back through the aortic valve and over the mitral valve, causing the mitral valve leaflets to vibrate. This is very difficult to hear in real life.
Aortic regurgitation is caused again by idiopathic age-related weakness, but it's also worth remembering that it can be caused by connective tissue disorders, such as Ehlers-Danlos syndrome or Marfan syndrome, where patients with these conditions have difficulty in creating strong connective tissues, leading to weakness of the valve leaflets. So thanks for watching, I hope you found this video helpful. If you did, don't forget there's plenty of other resources on the Zero to Finals website, including loads and loads of notes on various different topics that you might cover in medical school with specially made illustrations.
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