An infant heart murmur has been described as a rumbling, humming, vibration, or swishing. Most infants that have a heart murmur are perfectly healthy, as this can occasionally happen when the blood suddenly flows a little faster than normal. The only symptom of this condition is a sound that is clearly different from the typical beat of the heart, and it is usually only heard through a doctor's stethoscope. When the murmur is suggestive of an actual heart condition, the symptoms tend to include blue skin, sweating, quick breathing, chest pain, and dizziness.
In most cases, an infant heart murmur is considered harmless, and as such, it is typically called innocent or functional. In fact, most children will experience a heart murmur witnessed by their pediatrician at least once in their lifetime. It is usually caused by blood moving faster than usual, or in higher amounts than usual. Anemia, fever, and hyperthyroidism are usually to blame for an innocent heart murmur in an infant, and it usually requires no treatment since no harm is typically done. There are no additional symptoms in the case of a functional murmur.
On the other hand, sometimes an infant heart murmur is cause for concern since it can signal congenital heart defects, which are usually formed in the womb as a result of the unborn baby's heart not developing correctly. Most of the time, congenital septal defects are to blame, as they are holes in the septum, which is the wall that is supposed to separate the two sides of the heart. Congenital valve defects are sometimes also the cause of an infant heart murmur, as some valves are too narrow or leaky to allow blood to flow through properly. Endocarditis, in which the lining of the heart is inflamed due to bacteria, may injure the heart valves enough to result in a murmur. Rheumatic fever can also damage the heart, causing infant heart murmur, which is why it is important to get bacterial infections cleared up before they can cause further damage to the body.
Symptoms of babies with abnormal heart murmurs usually include failure to grow, lack of appetite, and blue skin, particularly in the mouth and on the fingertips. Other symptoms may indicate distress, including sweating, fast breathing, dizziness, extreme fatigue, chest pain, and even fainting. Such babies usually need to see a doctor, who can diagnose the issue based on the pitch, length, and location of the murmur. The infant heart murmur will usually disappear once the underlying issue is treated, typically using medicine or surgery.