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Cardio Exam

The First Heart Sound

March 4th, 2023
On this page:Loud S1Soft S1


The first heart sound (S1) indicates closure of the mitral and tricuspid valves.
S1 is normally heard best over the apex.

Loud S1

  • Listen For

  • Increased intensity of the first heart sound.
  • Causes of a Loud S1

  • Mitral stenosis
  • Hyperdynamic circulation - exercise, infection, hyperthyroidism, pregnancy

Soft S1

  • Listen For

  • Reduction in intensity of the first heart sound.
  • Causes of a Soft S1

  • Mitral regurgitation
  • Ventricular septal defect
  • First degree heart block
  • Left bundle branch block
  • Myocardial depression
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