• Normally, blood flow within the heart is smooth, or laminar.
    • This is like the flow in the middle of a wide river, it is smooth and makes little sound
    • In the heart, one just hears the normal sounds of the valves closing
      • These heart sounds are the classic “lub-dub”, or S1 and S2
  • Blood flow within the heart can become turbulent, or non-laminar
    • This is like water flow in a rapid where it is rough, and makes much noise
    • In the heart, one can hear a murmur, signifying turbulence
      • The causes of murmurs are:
        • leaking valves
        • tight valves
        • holes between the different chambers of the heart
  • Murmurs do not always correlate with the severity of disease
    • In leaky valves
      • The murmur is affected by
        • The amount of leak
        • The amount of force that the blood is being pumped with
          • Like when you turn up the faucet on a hose, it makes more noise
        • The pressure in the receiving chamber
    • So, in mitral regurgitation, there are some murmurs that are usually going to turn out to be relatively minor leaks
      • Intermittent murmurs
      • Soft, musical murmurs
    • The rest of the murmurs need other diagnostics to tell how severe they are (echocardiogram, radiographs)
    • All dogs with murmurs should have, at the very least, a set of radiographs taken to see if they have heart enlargement
      • These should be followed over time
    • All cats with murmurs should have an echocardiogram performed to see if it is significant
      • about 15% of cats can have heart disease without a murmur


  • Some murmurs do correlate pretty well with severity of disease
    • With “tight” valves, seen with congenital (from birth) subaortic or pulmonic stenosis
      • The murmur can correlate pretty well with how severe the disease is
        • An echocardiogram is necessary, however, to determine actual severity


 

 

  • In some murmurs, the louder the better!
    • With a hole between the two ventricles (ventricular septal defect)
      • The smaller the hole, the louder the murmur


  • If a murmur is heard in a pet, that murmur should be investigated further
    • In dogs
      • Radiographs (X-rays)
        • Radiographs can tell how big the heart is, but not what is going on inside the heart
      • Echocardiogram (heart ultrasound)
        • An echocardiogram can definatively diagnose the disease and severity of disease
        • It cannot tell if there is fluid in the lungs
          • So, if a dog is coughing in addition to a murmur, radiographs will be required in addition to the echocardiogram
    • In cats