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Loud first (1st) heart sound

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

A loud first heart sound occurs when the leaflets are wide open at the end of ventricular diastole and shut forcefully at the beginning of ventricular systole.

Possible causes of a loud first heart sound include:

  • late atrioventricular closure
    • this occurs when there is rapid flow at the end of diastole e.g. mitral stenosis, the short diastole of tachycardic states and left to right shunts
    • where the P-R interval is less than 0.12 s. This situation results in an opened valve that is not closed at the time of ventricular contraction.

Hence:

  • atrial fibrillation
  • short diastole - tachycardia
  • atrial premature beat
  • mitral stenosis where high left atrial pressure delays mitral valve closure

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The content herein is provided for informational purposes and does not replace the need to apply professional clinical judgement when diagnosing or treating any medical condition. A licensed medical practitioner should be consulted for diagnosis and treatment of any and all medical conditions.

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