What is the clinical significance of an S3 sound on auscultation?

An S3 heart sound (ventricular gallop) can be benign in children, but when it occurs in adults, it is usually indicative of severe mitral valve regurgitation or congestive heart failure. It occurs immediately after S2, at the beginning of ventricular diastole and is caused by increased volume of blood within the ventricle. Right and left sided S3 sounds can be distinguished based on their association with respiration; a right-sided S3 will increase on inspiration, while a left-sided S3 will increase on expiration.

An S4 sound (atrial gallop) occurs immediately before S1, while the atria are in systole. It is typically caused by the atria contracting forcefully in an effort to overcome ventricle hypertrophy (due to long-standing hypertension, aortic stenosis) or fibrosis (due to collagen vascular disease, cardiac damage).

When considering heart sounds, recall that S1 and S2 are produced by closing of the atrioventricular valves (mitral and tricuspid) and semilunar valves (aortic and pulmonic), respectively.

Extra heart sounds (S3, S4) are best heard with the bell-side of the stethoscope (used for lower frequency sounds).

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This post was written by Omar Rifai