Every 24 seconds, a drop of blood circulates through the entire body and returns to the heart, ready to be pumped out again. In about 1 out of 20 people, the pumping action sometimes creates a sound called a heart murmur, which is different from the typical 'lubb-dubb' heart beat made by the heart valves slamming shut. While not loud enough to be detected by an ear on the chest, it can be picked up with the aid of a stethoscope. Murmurs are the result of turbulence in the blood flow, much like the noise of rapids in a river. 

  Most heart murmurs have no medical consequences, and do not require any treatment. Soft murmurs are almost universal at one time or another during childhood, but are usually outgrown by the time the child reaches adolescence. Other murmurs, however, can signal disease or cardiac abnormalities.

  Heart murmurs are categorized according to whether they occur in the pumping (systolic) or relaxation (diastolic) phase of the heart beat. Murmurs that are audible throughout both phases are termed 'continuous' murmurs. In addition to its timing, a heart murmur's location and character give your physician important clues to its causes. 

  Heart murmurs that occur during the pumping phase often are innocent, showing no evidence of anything harmful. By contrast, continuous murmurs and those that are heard during the relaxation phase are usually due to some disease or faulty flow of blood through the heart. These may or may not be serious, but always warrant further investigation.

  After a physician's initial testing with a stethoscope, echocardiograms may be ordered. This procedure uses ultrasound and, sometimes, Doppler microphones to provide a detailed visual image of the heart in action. Additional tests may include chest X-rays and electrocardiograms, which are heart wave patterns obtained by placing electrodes on the chest.

There are many causes of heart murmurs, including:

• minor structural irregularities in the heart valves. These produce innocent murmurs.
• a larger than usual amount of blood flowing through the heart — a condition seen, for example, in pregnant women and athletes. This type of murmur is also innocent.
• a narrowed valve that obstructs the blood flow. These can be serious.
• a leaky valve that allows blood to back up through it. The seriousness of these murmurs depends on the severity of the leak.
• a hole in the partition between the heart's right and left sides. The seriousness must be judged on a case-by-case basis.
• a floppy mitral valve, where valve closure is imperfect and blood slips backward. Here, too, the potential harm must be gauged on an individual basis.