Heart Murmurs and Their Grades

Heart Murmurs can be functional (innocent) or organic and are caused by turbulence of flow in the heart or blood vessels, which causes vibrations of the heart or vessel walls, perceived as murmurs by the examiner. The louder the murmur, the more likely it is to be pathologic. Functional, benign, or innocent murmurs are usually soft (grade I or II) and usually occur in systole.

Descriptions of murmurs usually include:

  • timing (diastolic or systolic)
  • intensity (soft or loud – grading of heart murmurs described below)
  • pitch or sensation of frequencies (high or low pitched)
  • position (where the murmur is loudest – mitral area, aortic area, etc)
  • radiation ( in which direction the sound of the murmur travels)
  • tonal quality (blowing, rumbling, etc)

When an examiner first hears a murmur, he/she must determine whether the murmur is a functional or innocent murmur, or whether it is an organic murmur.

Functional murmurs are characterized by being well-localized, short, early or mid-systolic, grade 1 or 2/6, and diminished in intensity when the patient stands, sits up, or strains during a Valsalva maneuver.

Organic murmurs do not fit the pattern of functional murmurs. They are long or loud, greater than grade 2/6, often diastolic, and associated with other abnormal cardiac findings. They also intensify with the strain of the Valsalva maneuver.

Grading of murmurs:

I – is a murmur barely audible with stethoscope. It is soft, heard intermittently, always with concentration and never immediately.

II – is a murmur that is low, but usually audible. It is soft, audible immediately and with every beat.

III – is a murmur of medium intensity without a thrill. It is easily audible, and relatively loud.

IV – is a murmur, which is of medium intensity with a thrill, is relatively loud, and is associated with a palpable thrill.

V – is the loudest murmur heard with stethoscope on chest. It is loud enough to be heard by placing edge of the diaphragm of stethoscope over the patient’s chest. It is associated with a palpable thrill.

VI – is a murmur heard with stethoscope off the chest. It is so loud it can be heard even when the stethoscope is not in contact with the chest and is held slightly above the surface of the chest. It is associated with a palpable thrill.

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