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Heart Sounds Research Lab
Fourth Heart Sound (S4)
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The Heart Sounds and Murmurs Laboratory | 6560 Fannin St, Suite 1836| Houston, Texas 77030 | 832-355-2937
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The fourth heart sound (S4) is a low frequency sound, generally in the 30 to 50 cycle-per-second range. S4 is best heard with the bell of the stethoscope and tends to be blunted or ablated by use of the diaphragm, or by pressure exerted upon the bell. A left-sided S4 is best heard at the apex but may radiate broadly over the precordium.
Fourth Heart Sound (S4)