Fundamentals of Heart Sounds

Using Auscultation Lessons

Here we provide an example of a murmur. In this case, Aortic Stenosis.

Playback

Click the playback button on the torso to hear a short recording.

The patient was sitting during auscultation.

Phonocardiogram

A phonocardiogram is a plot of the sound's amplitude over time. Click the play button to view this phonocardiogram and hear the corresponding lung sound. This video will loop until paused.

Introduction

Twelve heart sounds have been selected for of this introductory auscultation course. Each lesson, described below, includes a textual description, audio recording, and a video. Optionally, a quiz can be taken to measure comprehension and listening skills.

Normal Heart Sounds

The closure of the mitral and tricuspid valves creates the first heart sound. The mitral valve usually closes first, immediately followed by the tricuspid valve. Closure of the aortic and pulmonic valves creates the second heart sound.

This recording is a normal first and second heart sound with a rate of sixty beats per minute. The stethoscope's diaphragm is positioned at the apex (mitral valve area). Usually, the first heart sound is somewhat louder than the second heart sound when auscultating at the Apex. Sound intensity will vary with the chestpiece's position as well as with the patient's anatomy.

In addition to sound intensity, the first heart sound (S1) can be identified by its timing. At moderate heartbeat rates, the first heart sound follows the longer pause.

Splitting Second Heart Sound

When the aortic and pulmonic valves close, sounds are created. Normally a combined sound is heard, which is the second heart sound (S2). If these two components can be individually distinguished, the condition is called a physiological split.

Careful analysis of the splitting and intensity of the second heart sound can indicate the presence of many cardiac abnormalities.

While listening to the audio recording, observe that splitting varies between zero and eighty milliseconds depending on the respiratory cycle phase.

In physiologic splitting, the maximum separation between aortic and pulmonic components of the second heart sound occurs at peak inspiration.

In paradoxical splitting, the maximum separation occurs at peak expiration. Paradoxical splitting can occur with left bundle-branch block (LBBB) and aortic stenosis, both of which cause the aortic valve closure to be delayed until after the pulmonic valve closure, reversing the normal sequence of events.

Split Second Heart Sound - Lesson, Recording, Video

Fixed Splitting Second Heart Sound

When the separation of the two components of the second heart sound remains unchanged through inspiration, the split is called a fixed split.

The inability of the ventricles to change their volume with respiration causes the splitting. Fixed splitting of the second heart sound (along with murmurs) indicates the presence of heart disease or a heart defect.

Fixed Splitting Second Heart Sound - Lesson, Recording, Video

Third Heart Sound

A third heart sound (S3) occurs early in diastole, just after the second heart sound. S3 is a low-frequency sound best heard using the bell of the stethoscope pressed lightly on the skin of the chest. Position the chestpiece at the left lateral sternal border (LLSB) or xiphoid area.

Sudden deceleration of blood flow into the left ventricle from the left atrium causes the third heart sound. In the anatomy video, observe the thin-walled, dilated left ventricle with generalized decreased vigor of contraction.

In the presence of a third heart sound (S3), the first heart sound decreases in intensity while the second heart sound increases in intensity

In young people and athletes, it is a normal phenomenon. In older individuals, it indicates the presence of heart disease.

Fourth Heart Sound

The fourth heart sound occurs in late diastole, just prior to the first heart sound. The fourth heart sound is a low-frequency sound best heard with a chestpiece bell pressed lightly onto the skin.

The fourth heart sound occurs during the diastolic filling phase, created by increased stiffness of the left ventricle, decreased ventricular compliance, or by increased volume. This may be a manifestation of heart disease. A fourth heart sound is never heard with atrial fibrillation because the contraction of the atria is ineffective in this condition. Review the anatomy video for an example.

The first heart sound is decreased in intensity and the second heart sound is increased in intensity.

Fourth Heart Sound - Lesson, Recording, Video

Innocent Murmur

Innocent murmurs are benign continuous sounds observed in pediatric patients with non-cardiac conditions such as pregnancy, hyperthyroidism, exercise, and anemia. When treated appropriately, the systolic murmur disappears.

Short duration and mid-range frequency characterize an innocent murmur. The stethoscope bell or diaphragm can be used.

In this recording, S1 and S2 are normal. Diastole is silent.

Innocent Murmur - Lesson, Recording, Video

Mid-Systolic Click

The mid-systolic click is usually created by the sudden prolapse of the mitral valve leaflet into the left atrium. The anatomy video illustrates this mitral valve posterior leaflet prolapse.

Listen to the recording of a mid-systolic click recorded at the apex. The first and second heart sounds are normal, and no murmur is present.

In some cases, a late systolic murmur follow the mid-systolic click.

Mid-Systolic Click - Lesson, Recording, Video

Mitral Valve Leaflet Prolapse

In this case, a mid-systolic click is immediately followed by a late systolic diamond-shaped murmur that runs to the end of systole. The intensity of the murmur increases and its starting point begins earlier in systole as left ventricular volume decreases (going from supine to standing).

On the anatomy video you can see that the murmur is caused by the prolapse of the posterior mitral valve leaflet. The murmur is represented by turbulent flow from the left ventricle into the left atrium.

Mitral Valve Leaflet Prolapse - Lesson, Recording, Video

Aortic Stenosis

This case presents a diamond-shaped systolic murmur associated with aortic stenosis. The first and second heart sounds are normal. The murmur starts in systole, shortly after the first heart sound and ends before the second heart sound.

The murmur is mid to high-pitched and is usually auscultated with the chestpiece diaphragm.

The anatomy video shows a markedly thickened left ventricle. The aortic valve leaflets are thickened and immobile. The murmur is caused by turbulent flow across the stenotic aortic valve.

Aortic Stenosis - Lesson, Recording, Video

Aortic Regurgitation

Aortic regurgitation produces a decrescendo murmur starting early in diastole. The first and second heart sounds are normal. The decrescendo murmur is high-pitched.

Aortic diastolic murmurs can be heard at the right sternal border, third and fourth intercostal spaces.

The anatomy video shows an enlarged left ventricle with normal contractility. Observe the regurgitant flow from the aorta into the left ventricle, which causes the murmur.

Aortic Regurgitation - Lesson, Recording, Video

Mitral Regurgitation

This case presents an example of a pansystolic murmur usually associated with mitral regurgitation.

The murmur is a mid-frequency, rectangular murmur taking up all of systole. S1 is normal. S2 is single. There is a third heart sound gallop in diastole. Both the left ventricle and the left atrium are enlarged. The murmur is caused by turbulent flow through the incompetent mitral valve leaflets into the left atrium.

In the anatomy video, observe the enlarged left ventricle and left atrium and turbulent flow from the left ventricle into the left atrium, creating the murmur.

Mitral Regurgitation - Lesson, Recording, Video

Mitral Stenosis

This case presents an example of moderate mitral stenosis. The first heart sound is increased in intensity, while the second heart sound is normal and unsplit. A diamond-shaped low-frequency murmur follows the opening snap. There is a second murmur in late diastole caused by the contraction of the left atrium. Use the bell of the stethoscope to hear this murmur.

In the animation, observe the turbulent blood flow from the left atrium into the left ventricle. Also, observe the moderately thickened mitral valve leaflets and the moderately enlarged left atrium.

This condition is most commonly due to rheumatic heart disease.

Mitral Stenosis - Lesson, Recording, Video