We are now going to tune in on the systolic auscultatory events at the apex. We’re going to listen on this occasion with the diaphragm of the stethoscope and we are going to hear the s1 obscured by the beginning of the systolic murmur. Now, the systolic murmur will then occur, the systolic murmur is throughout all of systole – actually, it goes just beyond the second heart sound. Why? Because of the pressure curves, because in this particular case, the left ventricular pressure curve is exceeding that of the left atrium and stays above it from s1 to just beyond s2. We will appreciate the frequency of the systolic murmur – high frequency – and we’ll see the shape of the murmur, that is, plateau-shaped, holosystolic, plateau-shaped, high in frequency.

Let’s all listen together at the apex, and we’re even going to observe this on the oscilloscope. Let’s all listen carefully together.

Oscilloscopic image of murmur

By freezing the oscilloscopic image and simultaneously listening, we can further appreciate these auscultatory events.

Murmur location and radiation

Murmurs may be characterized by descriptors that include location, timing, contour, and frequency. The murmur is best heard at the apex, or mitral area, and this location is related to the underlying lesion. The left ventricle is anterior to the left atrium, and regurgitation through the mitral valve usually results in turbulent posterior flow, with radiation of the murmur toward the axilla.

MR heart animation

This is a graphic example of the heart in a patient with mitral regurgitation. In the animation that follows, we can appreciate that the murmur is generated across the regurgitant mitral valve during left ventricular systole.

Aortic pressure curves

These simultaneous left atrial, left ventricular, and aortic pressure curves illustrate the relationship of the hemodynamic events to the timing, contour, and frequency of the systolic murmur. The murmur begins with mitral closure, obscuring the first heart sound. It continues up to and through aortic closure, as left ventricular pressure exceeds left atrial pressure throughout this period. The murmur is plateau-shaped because there is a significant pressure gradient between the left ventricle and left atrium throughout all of systole. The murmur is high in frequency, primarily because blood is flowing from the high-pressure left ventricle to the low-pressure left atrium.

Tune in to diastole

We are now going to tune in to diastole in this patient and listen very carefully. In this case, we shall be using the bell of the stethoscope and we are going to hear two compelling types of acoustic events. The first is a third heart sound, and following that, a rumble. Now, what could be the cause of a third heart sound in this patient? One of two possibilities. If the ventricle is poorly compliant, then when blood comes into that ventricle across the mitral valve, that stiff ventricle decelerates the blood in an exaggerated fashion, and you hear that booming, low frequency sound – the one we felt on the chest wall. In addition, the third heart sound, again, could be related to flow. If you have much flow coming across that mitral valve, as in mitral regurgitation, as in a shunt lesion, you can hear that s3, because there’s so much acceleration of blood into the ventricle, that even with normal deceleration, you generate that low-frequency, booming third heart sound. And then the rumble? Well, the genesis of that could be two-fold at least. Number one, this patient could have an element of mitral stenosis. In addition, you can get a rumble from flow alone, that if there’s enough blood coming across that mitral valve into the ventricle, it’s almost as if there is a relative mitral stenosis and you hear a rumbling sound. And speaking of relative mitral stenosis, once in a while, in a patient with aortic regurgitation, you hear that very special murmur at the apex called the Austin-Flint rumble, when the valve is relatively stenosed because the pressure is just a bit higher than normal in the left ventricle, pushing the mitral valve back. So now, let’s listen after understanding the physiologic descriptions of these possibilities. We’ll listen at the apex and we’ll correlate this with chest wall movement because, remember? We could palpate a third heart sound before. The movements of the chest wall will occur during systole and again during diastole, an early s3. [Cut-away] what a nice correlation of acoustics with chest wall movement! Let’s look at the oscilloscope to further appreciate this. By freezing the oscilloscopic image and simultaneously listening, we can further appreciate these auscultatory events.

Differential diagnosis

The differential diagnosis of a low frequency apical diastolic murmur includes: the murmur of mitral stenosis, the flow murmurs of significant mitral regurgitation and shunt lesions, and the Austin Flint murmur of significant aortic regurgitation. The interpretation of the murmur depends on both the findings on auscultation and the company it keeps with the remainder of the physical examination. The key auscultatory events at the apex include a holosystolic plateau-shaped murmur, best heard with the diaphragm, because of its high frequency; a third heart sound; and a rumbling murmur that is mid diastolic, short, and best heard with the bell of the stethoscope because it is low frequency.