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MEDizzy
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Kashvi Chakrabortyabout 4 years ago

What is a fourth heart sound?

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about 4 years ago

Fourth heart sound or S4 is a very-low frequency abnormal heart vibration which occurs upon atrial contraction to force blood into the non-compliant left ventricle. S4 is heard before S1. The sound occurs as a result of blood striking the walls of left ventricle. In conditions such as atrial fibrillation, the atria do not contract therefore there is no chance for the occurrence of S4.

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