Cardiac Auscultation
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  • Click here to see an image and explanation of the cardiac cycle and murmur characteristics.
  • Click here to see an image of a blood flow diagram.

  • The gelding had a regular rhythm and all 4 heart sound were ausculted.
  • All 4 valve areas should be ausculted.
  • In many horses all four heart sounds can be detected, although they are usually not all heard at the same location as their points of maximal intensity vary.
  • The fourth heart sound occurs in late diastole and is heard best in the left ventricular inlet region, just dorsal to the mitral valve area.
  • The first heart sound occurs at the onset of systole and is best heard at the left apex in the mitral valve region.
  • The second heart sound occurs at the end of systole and is best heard at the left base over the aortic valve area.  The pulmonic component of the second heart sound is best heard in the pulmonic valve area.
  • The third heart sound occurs in early diastole and is best heard over the left apex in the mitral valve area.
  • The normal rhythm is sinus but 15-18% of horses have second degree A-V block during a routine resting examination.
  • Systolic ejection murmurs occur frequently in normal horses and are usually grade 1-3/6 early, mid, late or holosystolic murmurs with a crescendo-decrescendo quality that are best heard over the left heart base in the aortic and pulmonic valve areas.
  • Early diastolic murmurs are also common and occur most frequently between the second and third heart sounds and have a decrescendo quality with their point of maximal intensity over the right or left ventricular inlets, above the tricuspid and mitral valves.

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