Let us listen at the apex with light pressure on the bell using the carotid vessel as our timing mechanism.
What is the precise significance of these acoustic events at the apex? Well, to begin with, the most compelling thing we heard was a diastolic low frequency murmur. But we can describe it even better. It was long, it was presystolic, accentuation. During diastole, the mitral valve should be wide open to allow blood to come from the left atrium to the left ventricle. But this tells us that valve is narrowed and, therefore, there was rumbling across that valve as blood goes from the left atrium to the left ventricle. It is a long murmur, telling us there is gradient across that valve throughout essentially all of diastole and there is presystolic accentuation, as the atrium contracts and that kick accelerates the blood across the valve and you get a diastolic accentuation just before the first heart sound. So, these are the factors that tell us this is not only mitral stenosis, but that it is likely severe, because it is a long murmur. In addition, we must pay attention to the first heart sound and the opening snap. The first heart sound in this case was loud, and there was an opening snap right after the second heart sound, and it was close into the second heart sound.
Now, why is the first heart sound loud? well, it is loud because with mitral stenosis, that valve is held open quite a long time during diastole. It is held open because of the high, high left atrial pressure. Then, when the ventricle contracts, it has a long excursion to make to go back and when those valves coapt and come together, they are also more fibrous that a normal valve because of the mitral stenosis, so you hear an accentuated first heart sound. In addition to that, the opening snap occurred. That occurred after the second sound as the valve opened. And that occurred close to the second sound, because the left atrial pressure in this severe case of mitral stenosis was high and the valves were thrown open early. That opening snap also told us that the valve was still pliable, not all calcified and rigid.
So, in summary, we heard the classic acoustic events at the apex of a patient with severe mitral stenosis. [ mimicking sounds ] don’t forget that cadence, because it tells us: long murmur, severe mitral stenosis. Opening snap, early on, also severe mitral stenosis. Loud first heart sound, also mitral stenosis and, that opening snap, that also tells us that that valve is still pliable. A typical group of acoustic events at the apex in such a patient.
By viewing an oscilloscopic image and simultaneously listening, we can further appreciate these auscultatory events The murmur is best heard at the apex, or mitra area, and the location is related to the underlying lesion. The left atrium is posterior to the left ventricle, and flow through the stenosed mitral valve results in turbulent anterior flow toward a localized area at the apex. This is a graphic example of the heart in a patient with mitral stenosis. in the animation that follows, we can appreciate that the murmur is generated across the stenosed mitral valve during left ventricular diastole.
these simultaneous left atrial and left ventricular pressure curves illustrate the relationship of the hemodynamic events to the timing, contour, and frequency of the murmur.
the murmur begins with the opening of the mitral valve as atrial diastolic flow enters the left ventricle. it is long, as a gradient between the left atrium and left ventricle persists throughout all of diastole. there is an early diastolic accentuation of the murmur, as most diastolic flow occurs at this time, and a presystolic accentuation, as left atrial contraction again augments flow.
the murmur is low frequency, primarily because blood is flowing from the relatively low pressure left atrium to the low pressure left ventricle. The key auscultatory events at the apex include:
a rumbling diastolic murmur that is long with presystolic accentuation and is best heard with the bell of the stethoscope because of its low frequency;
an early opening snap that occurs approximately five hundredths of a second after the aortic component of the second heart sound; and a loud first heart sound.