Third and Fourth Heart Sounds

Third Heart Sound Gallop Lesson #677

patient thorax when auscultating by stethoscope

The patient was supine during auscultation.

Description

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.

Phonocardiogram

Anatomy

Third Heart Sound Gallop

Authors and Sources

Authors and Reviewers

Heart sounds by Dr. Jonathan Keroes, MD and David Lieberman, Developer, Virtual Cardiac Patient.
Lung sounds by Diane Wrigley, PA
Respiratory cases: William French
David Lieberman, Audio Engineering
Heart sounds mentorship by W. Proctor Harvey, MD
Special thanks for the medical mentorship of Dr. Raymond Murphy
Reviewed by Dr. Barbara Erickson, PhD, RN, CCRN.
Last Update: 11/10/2021

Sources

Heart and Lung Sounds Reference Library Diane S. Wrigley
Publisher: PESI
Impact Patient Care: Key Physical Assessment Strategies and the Underlying Pathophysiology
Diane S Wrigley & Rosale Lobo
Practical Clinical Skills: Lung Sounds
Essential Lung Sounds Diane S. Wrigley, PA-C
Published by MedEdu LLC
PESI Faculty - Diane S Wrigley
Case Profiles in Respiratory Care 3rd Ed, 2019
William A.French
Published by Delmar Cengage
Essential Lung Sounds by William A. French
Published by Cengage Learning, 2011
Understanding Lung Sounds Steven Lehrer, MD
Clinical Heart Disease W Proctor Harvey, MD
Clinical Heart Disease
Laennec Publishing; 1st edition (January 1, 2009)
Heart and Lung Sounds Reference Guide
PracticalClinicalSkills.com