What did we hear together at the lower left sternal edge? We heard a diastolic murmur. We're going to go back and listen again together and you will note that when the carotid impulse occurs, that part of the cardiac cycle, that is, systole, is silent and the murmur is in diastole. Again, we're going to use the bell of the stethoscope. Everyone listen together. [Cut-away]
At the lower left sternal edge, with light pressure on the bell, we first, of course, heard the expected [sounds], but we also heard in addition, in diastole a low frequency, rumbling type of murmur. So we heard [sounds].
What do you think of when you hear such a murmur in this area? Well, there are at least two possibilities. Could it be that this patient has some degree of stenosis of an AV valve in this area? That's a possibility. Another possibility is a murmur such as this could be due to flow alone, where the valve itself is not narrowed, the AV valve, but rather, the amount of flow going across that valve relative to the orifice size is high and, therefore, a rumbling sound occurs and you hear that same sequence of acoustic events [sounds]. Which one is it?
Murmur oscilloscope
By viewing an oscilloscopic image and simultaneously listening, we can further appreciate these auscultatory events. [Sounds]
Differential diagnosis
The differential diagnosis of a mid diastolic murmur at the lower left sternal edge includes the right ventricular filling murmur resulting from either significant tricuspid regurgitation or a large left-to-right atrial level shunt. While low frequency in our patient, this murmur is usually mid frequency or higher. Other causes of a diastolic murmur in this location include tricuspid stenosis and pulmonic valve regurgitation. These murmurs differ from that in our patient both in timing within diastole and in their acoustic qualities. Proper interpretation of the murmur depends upon other auscultatory findings as well as the company it keeps with the remainder of the physical examination.
Inspiratory increase in intensity
An inspiratory increase in the intensity of the auscultatory events typically identifies their right-sided origin. The absence of an inspiratory increase in the intensity of our patient's mid diastolic murmur is typical of an atrial septal defect, as the common atrial reservoir results in constant high right ventricular filling volume.