Heart Sounds Research Lab
Third Heart Sound (S3)
The Heart Sounds and Murmurs Laboratory | 6560 Fannin St, Suite 1836| Houston, Texas 77030 | 832-355-2937
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Some characteristics of a third heart sound (S3):

1. It occurs at the beginning of diastole after S2 and is lower in pitch than S1 or S2 as it is not of valvular origin.

2. Close to 100-110msec interval between S2 and the S3.

3. The third heart sound is benign in youth, some young adult athletes, and sometimes in pregnancy but if it re-emerges later in life it may signal cardiac problems like a failing left ventricle as in dilated congestive heart failure (CHF).

4. An S3 heart sound indicates increased volume of blood within the ventricle.

5. An S3 heart sound is best heard with the bell-side of the stethoscope (used for lower frequency sounds).
Third Heart Sound (S3)