What did we learn together by listening at the upper left sternal edge? We learned a lot. We're going to go back now and we're going to tune in, we're going to focus, particularly on the murmur we heard, although there is much more, but let's start by really focusing on that murmur. We'll use the diaphragm of the stethoscope again, the cotton swab to identify systole by placing it on the carotid vessel. Let's listen together and focus on the murmur. [Cut-away]
There is so much diagnostic information we have at the upper left sternal edge on auscultation. We focused, however, on the murmur and first we characterize it. To begin with, the murmur is clearly systolic, it occurred at the time of the carotid artery impulse, as reflected by the cotton swab; the second thing is that the murmur's configuration was crescendo-decrescendo; and the third thing is that the length of that murmur was short, occurring in early systole. Now, what do we think of when we hear a murmur like that at the upper left sternal edge? To begin with, we think flow, even normal flow in patients with dynamic circulation, such as in youth, can generate such a murmur. Or, could there be excess flow going out across the outflow tract and the pulmonary valve. Could that be the genesis of this murmur or could there be obstruction somewhere in the outflow tract of the right ventricle that is located here anatomically? Albeit, it would be minor because the length of the murmur was relatively short. Those are our differential diagnostic considerations.
Murmur oscilloscope
By viewing an oscilloscopic image and simultaneously listening we can further appreciate these auscultatory events.
Murmur's Descriptors
Murmurs may be characterized by descriptors that include: location, timing, contour and frequency.
Murmur
The murmur heard at the upper left sternal edge is systolic, short, early peaking, crescendo-decrescendo and mid frequency. Murmurs at the upper left sternal edge that occur early in systole typically result from turbulent blood flow when the majority of blood is ejected from the right ventricle.
Pressure curves
These simultaneous pulmonary artery and right ventricular pressure curves illustrate the relationship of the hemodynamic events to the timing and contour of the murmur. The murmur begins after opening of the pulmonary valve as right ventricular pressure exceeds pulmonary artery pressure early in systole. The crescendo-decrescendo configuration of the murmur is related to blood flow between the right ventricle and the pulmonary artery in systole. The short length of the murmur reflects enhanced blood flow without significant obstruction early in systole, when the majority of blood is ejected from the right ventricle.
Differential diagnosis
The differential diagnosis of a systolic, short, early peaking, crescendo-decrescendo murmur at the upper left sternal edge includes an innocent murmur from normal flow, the obstruction murmur of mild pulmonary stenosis and the murmur from increased pulmonary blood flow due to an atrial left-to-right shunt. The interpretation of the murmur depends on both the findings on auscultation and the company it keeps with the remainder of the physical examination.