Third and Fourth Heart Sounds

Introduction

This course presents third and fourth heart sounds. Before beginning this course, you should finish the Normal, First and Second Heart Sounds courses.

Overview

The third heart sound (S3) is a low-frequency, short vibration occurring in early diastole at the end of the rapid diastolic filling period of the right or left ventricle. S3 may be heard in normal children.

Third Heart Sound Gallop

In adults, hearing a third heart sound requires quiet. Ask the patient to exhale and hold their breath. Shift stethoscope bell around the apical and lower sternal area listening for a third heart sound gallop. The cadence is similar to 'Kentucky'.

Sound Patterns

As an introduction, we present two sound patterns that illustrate S3 and S4 gallops. We will cover these in the lessons that follow.

Third Heart Sound - Heart Disease

In adults over the age of 40, S3 can indicate heart disease, except for patients that are athletes. As you will hear in the lessons, S3 is a low-pitched sound, allowing the observer to distinguish S3 from a split S2.

Fourth Heart Sound Gallop

The fourth heart sound (S4) is a low-pitched, late diastolic sound. So it occurs shortly before the first heart sound. The stethoscope bell should be used, pressing lightly against the chest wall at the lower left sternal border or subxiphoid area. The cadence is similar to 'Tennessee'. S4 will often indicate a heart abnormality.

Lessons

Third Heart Sound Gallop

The third heart sound (S3) is a low-frequency sound best heard with the stethoscope bell, pressed lightly on the skin. A third heart sound occurs early in diastole. In the presence of S3, the first heart sound has diminished loudness. The second heart sound becomes louder.

Sudden deceleration of blood flow into the left ventricle from the left atrium causes the third heart sound. Observe the dilated, thin-walled left ventricle with generalized decreased contraction vigor in the cardiac animation video.

In young people and athletes, it is a normal phenomenon. In older people, S3 indicates congestive heart failure.

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.

Third heart sounds are also called ventricular gallops or S3 gallops.

Third Heart Sound Gallop Lesson

Fourth Heart Sound Gallop

In the recording, note that the fourth heart sound (S4) occurs in late diastole just before S1. The S1 intensity is decreased, while S2 intensity is increased. The fourth heart sound is low-pitched. Use the stethoscope bell, pressing lightly on the chest wall.

The fourth heart sound is generated by increased left ventricle stiffness due to scar tissue formation. This condition could be due to coronary heart disease.

Essential hypertension and aortic stenosis can also lead to fourth heart sounds. The anatomy animation video provides an example of S4.

Fourth Heart Sound Gallop Lesson

Third and Fourth Heart Sound Gallop

Listen to the recording of a third and fourth heart sound gallop. Note that the third and fourth heart sounds are low frequency. S4 has a pitch somewhat lower than S3.

Patients with heart failure will often have a third heart sound. As the patient's condition improves, this S3 becomes a third and fourth heart sound gallop.

Third and Fourth Heart Sound Gallop Lesson

Summation Gallop at 120BPM

With high heart rates, in this case 120 BPM, the diastolic interval is shortened. Accordingly, S3 and S4 sounds begin to merge, producing a single loud heart sound.

The cardiac animation video presents an enlarged left ventricle with decreased left ventricular contractility and a minimally enlarged left atrium.

Summation Gallop at 120BPM

Course Quiz

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Course Completion

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