Heart murmur

A murmur is a sound heard through the stethoscope alongside the normal heart sounds. It is not a disease in its own right: it is a sound, and that sound arises from the same thing as any heart sound, blood moving turbulently and making the structures it passes through vibrate. It is the same thing you hear in a garden hose, where the water makes no noise while it runs smoothly and starts to hum as soon as it churns.

When it is heard matters. Murmurs during systole, while the heart squeezes, can be one of two types: ejection murmurs, when blood has to cross a narrowed passage, and regurgitant murmurs, when a valve that should close lets blood flow backward. Murmurs during diastole, the phase when the heart relaxes, are a different story altogether: all diastolic murmurs are pathologic, with the exception of some third heart sounds.

And then there is the innocent murmur, which is called that for a reason. Up to 72 percent of children have a murmur at some point during childhood or adolescence. The mechanism is the same turbulent flow, only in healthy children and with no pathologic meaning.