🔹 S3 vs S4 Heart Sounds

🔹 S3 vs S4 Heart Sounds

• S3 (“ken-tuc-KY”)

  • Timing: Early diastole, just after S2.

  • Mechanism: Blood striking a dilated LV during passive filling.

  • Normal: Children, young adults, athletes.

  • Pathologic (age >40): LV dilation (eg, systolic HF with reduced EF).

  • Best heard: Apex, bell of stethoscope, left lateral decubitus.

  • Clinical action: If symptomatic (eg, dyspnea, hypoxemia) → IV diuretics.

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  S4 (“TEN-nes-see”)

  • Timing: Late diastole, just before S1.

  • Mechanism: Atrial contraction forcing blood into a stiff LV.

  • Cause: LV hypertrophy (eg, chronic hypertension, aortic stenosis).

  • Best heard: Apex, bell of stethoscope.