Extra Heart Sounds (S3 and S4)
This course will teach you about auscultation of the third and fourth heart sounds. Before you take this course you should have finished the Normal, First, and Second Heart Sound courses. You should feel comfortable with the material presented.
Using this course
Each lesson in this course includes text describing the heart or lung abnormality and a simulated torso indicating the stethoscope chestpiece location. An audio recording of the sound is provided. Phonocardiograms or waveforms are included with each lesson. These waveforms can be a highly useful aid in learning to recognize heart murmurs. In addition, short videos clips illustrate the heart's motion for each abnormality. These animations indicate the origin of each murmur. Blood flow is also animated. For lung sounds, the source (location) of the sound can be revealed.
After completing a lesson, use the lesson table of contents to navigate to another lesson.
When all lessons have been completed, we recommend using the auscultation practice exercises or quiz. In order to gain a certificate of achievement, please complete the course lessons and practice drill during one session. Most users complete the course's lessons and quiz in 30-45 minutes.
Authors and ReviewersAuthors: Jonathan Keroes, MD, Cardiologist (ret.), David Lieberman, Heart Sound Simulation Consultant. Medical review by Dr. Barbara Erickson.
Click To Begin Training Module
Lesson #1: Third Heart Sound Gallop
A third heart sound occurs early in diastole. In young people and athletes it is a normal phenomenon. In older individuals it indicates the presence of congestive heart failure. The third heart sound is caused by a sudden deceleration of blood flow into the left ventricle from the left atrium. In the anatomy video you will see a thin-walled, dilated left ventricle with generalized decreased vigor of contraction. In the presence of a third heart sound (S3) the first heart sound is decreased in intensity while the second heart sound is increased in intensity. The third heart sound is a low frequency sound best heard with the bell of the stethoscope pressed lightly on the skin of the chest.
Lesson #2: Fourth Heart Sound Gallop
The fourth heart sound occurs in late diastole just prior to the first heart sound. The first heart sound is decreased in intensity and the second heart sound is increased in intensity. The fourth heart sound is produced by an increase in stiffness of the left ventricle due to scar tissue formation. This may be a manifestation of coronary heart disease. A fourth heart sound can also be caused by a greatly thickened left ventricular wall such as with essential hypertension or aortic stenosis. This is shown in the anatomy video. A fourth heart sound is never heard with atrial fibrillation because the contraction of the atria is ineffective in this condition. The fourth heart sound is a low frequency sound best heard with the bell of the stethoscope pressed lightly on the skin of the chest.
Lesson #3: Third and Fourth Heart Sound Gallop
Both the third and fourth heart sounds (S3 and S4) are low frequency. S4 is lower than S3. This is a pattern that occurs with improvement of heart failure. That is, an S3 pattern gives way to an S3 S4 pattern as the patient improves.
Lesson #4: Summation Gallop at 120 beats per minute
At a heart rate of 120 beats per minute, the diastolic period is shortened. This causes the third and fourth sound to be superimposed, creating a single loud sound. The anatomy video shows an enlarged left ventricle with decreased left ventricular contractility and a minimally enlarged left atrium.