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Still's murmur is a common form of benign pediatric heart murmur.It is most commonly referred to as a "vibratory murmur," and does not pose a threat to the life of a patient. Still's murmur is one of the most commonly found innocent murmurs in children.

Definition
50-90% of all children will be diagnosed with a heart murmur at some point in their lives. Only 1% will threaten the health of the child. Still's murmur is considered an innocent or functional murmur, meaning it is not due to a defect, but just due to conditions surrounding the heart, and does not require medical follow up or treatment. Most innocent murmur sounds are caused by turbulent sound waves starting from either the heart or the vascular system.

This type of murmur usually occurs in children two to five years of age, but can occur outside of that range. Still's murmur is the most prevalent form of innocent murmur in school children (75%-80%).

History
Still’s murmur was discovered by and named after George Frederic Still. Still first described Still’s murmur in his pediatric textbook, Common Disorders and Disease of Childhood, in 1909. Still could not have discovered this innocent murmur without a stethoscope. Still first noticed the innocent murmur in his pediatric patients. Subsequently, he followed the patients over a period of years, and concluded this murmur was harmless. It has continued to be considered harmless to this day.

Over time, many theories have been proposed for the cause of this phenomenon. The origin of Still's murmur is still not agreed upon by all. The most popular theory for the cause of Still’s murmur is the vibrations of the chords of the septal leaflet of the tricuspid valve that are manufactured by ventricular ejection. There are at least two additional theories regarding the origin of Still’s murmur. One theory being the moderator band located in the right ventricle was the source of the Still’s murmur’s sound. The second theory suggests the chordae tendineae or "false chords" found in bicuspid and tricuspid valves of the heart might be strummed like a harp during sytole, causing the murmur. This theory was discounted, however, when it was considered that these structures are flaccid during the part of contraction in which the murmur manifests itself. A well known analogy was created to assist lay people in understanding what Still’s murmur sounds like. He described it as musical sound: like “the Aeolian harp’s strings set into vibration by the wind…and suggested false chords.”

Studies performed on adults suggest Still’s murmur originates in the aorta, and is usually out-grown in adulthood. One study supporting this idea was conducted on older adults with angina, believed to have aortic valvular sclerosis. It concluded that innocent murmurs found in children are not usually found in adults. Another study documented one exception to this idea in pregnant women who have blood viscosity and velocity similar to children’s, and can thus display similar sounding murmurs.

Diagnosis
Still's murmur is detected via auscultation with a stethoscope. It is generally described as a low-pitched, vibratory murmur, and most refer to it as having a "musical quality." The murmur can be heard best at the lower left sternal border.



The sound originates in the left ventricle. There are a number of current theories regarding the cause of the sound. One theory states that the murmur is caused by blood rushing across the openings of blood vessels branching off of the aorta, much like playing a flute. Another theory states that the sound is caused by vibration of the heart's own structures, such as the ventricular septum. This is supported by the fact that some children with Still's murmur also have minor defects of the ventricular septum, though never a large enough defect to manifest a health concern. The last prevalent theory proposes that Still's murmur is caused by increased cardiac output seen in particularly healthy children. This theory is supported by higher measured aortic flow rates and volumes in patients exhibiting Still's murmur. Since it is a benign murmur, not as much research has been put into its mechanism as other, more dangerous murmurs; thus, no one at this time is absolutely certain of its cause.

Signs and Symptoms
Since Still's murmur is benign in nature, it has no associated outward signs or symptoms. However, murmurs are affected by the position of the patient, in particular the supine position. This is due to an increase in stoke volume and ejection velocity when in this position. Other provocations that impact innocent murmurs include fever, anemia, anxiety, and exercise. During these high output states, the murmur becomes more audible. During a fever, the body's blood must flow faster to meet the needs of the immune system, therefore, the murmur may increase in volume, or a new one may manifest. The murmur will disappear or return to normal with the loss of fever. Anemia is a condition that causes a low concentration of red blood cells in the bloodstream, which in turn will cause blood to flow faster in order to meet the body's needs. Both anxiety and exercise increase heart rate, thereby causing an increase in blood flow through the heart, making the murmur more audible.

Treatment
There are no treatments for Still's murmur due to the fact that it is not a danger to the health of the patient. The murmur has a tendency to disappear around adolescence on its own. . Recent findings indicate 15%-20% of adults have a Still's murmur.

Society and Culture
While Still’s murmur is an innocent murmur, some patients experience anxiety because they have been diagnosed with a heart murmur. Parents of children diagnosed with Still’s murmur tend to experience significantly greater anxiety than the patients. In a study conducted on the families impacted by Still’s murmur, the parents were worried about a variety of issues. Their concerns included: the need for medicine (49%), facing sports restrictions (41%), the need for heart surgery (29%), other offspring also having Still’s murmur (20%), and early death (13%). Mothers worried that their actions during pregnancy caused the murmur (19%). Even after being reassured by the child’s doctor, 17% of parents were still anxious. After hearing from a cardiologist that the children would be fine, that number dropped to 7%. This is still a significant number. Awareness of the nature of Still's murmur and its harmless nature may help alleviate parental anxiety, so it is clearly important for information to be readily available to the public and for the public to take advantage of such resources.