What did we learn when we listened at the apex? Well, we listened with the bell of the stethoscope and it is the bell that brings out low-frequency sounds, so let’s use our carotid artery timing device again and listen again at the apex, thinking especially of low-frequency sounds. Let’s listen together. [Sounds]
What we heard with light pressure on the bell was a fourth heart sound that occurs just prior to systole. It is the same one we palpated previously when we evaluated the chest wall. That fourth heart sound tells us that we are pushing blood into the ventricle and the ventricle has a low compliance, and as blood accelerates and then is forced to decelerate rapidly into that non-compliant ventricle, you hear that fourth sound. Not just lub-dup, but bolup-dup, bolup-dup. And that fourth sound tells us that this is a non-compliant ventricle and it tells us something about the severity of the lesion in this case.
Now, after the fourth sound we heard the first sound and we heard our ejection sound, and it was much better heard at the apex, because the intensity of the murmur is less and it does not so much obscure the ejection sound, and then we heard the second sound. So, one more time, remember, it was that fourth sound at the apex that gave us the clue again that the lesion here is severe.
You know, one thing you can do with your stethoscope - it is so prominent in this case – if I can put some light pressure here and we can just observe the movement of the stethoscope and you can see the little presystolic impulse, and then we listen together and we hear while we watch the low-frequency sound at the same time the chest wall movement occurs.
Fourth sound graphic
This is a graphic example of a fourth heart sound, a first heart sound, and an ejection sound. Note that the fourth heart sound is low frequency and the first sound and ejection sound are high frequency.