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Third Heart Sound Gallop Lesson

Virtual Auscultation

patient torso with stethoscope chestpiece

patient position during auscultation
The patient's position is supine.


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.


Heart Sounds Video

Authors and Sources

Authors and Reviewers


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