What is a heart murmur?

Heart murmurs are common in children.  When a doctor listens to a child’s heart with a stethescope, they normally hear a “lub-dub, lub-dub, lub-dub” noise.  Occasionally there is an extra noise so we now hear “lub-shh-dub, lub-shh-dub, lub-shh-dub”.

By far the most common type of murmur we hear falls into the “innocent” category which means we are hearing the normal flow of blood round the heart which is more vibratory in some children, especially if they have a bit of a fever or are anaemic.  The child is usually very well and growing normally and the murmur is only picked up incidentally when they go to the doctor with a chest infection.  Most experienced GPs and paediatricians will be able to pick out the innocent murmurs in children over the age of 2 and may feel that a referral to a paediatric cardiologist is not warranted.  Under the age of 2 it is a bit harder to be sure that the murmur is innocent and this age group usually do end up seeing a cardiologist if the murmur is persistent.

Newborn babies often have murmurs in the first 24 hours of life which disappear over the first couple of days as various “short cuts” in their circulation close off as they adapt to life outside the womb.  Recent studies have shown that it is worth measuring the oxygen saturation of a baby’s blood if they still have a murmur on day 2 of life as lower oxygen saturations may point to there being something structurally not quite right with the baby’s heart.  Just less than 1 in 100 newborn babies have some sort of congenital heart problem ranging from a tiny hole between the main pumping chambers of the heart which will close up itself over the first weeks of life to a serious plumbing problem that necessitates major heart surgery in the first few days of life.  In these babies the murmur is caused by turbulence around leaky or partially blocked valves or the pressure of blood being pushed through a hole between either the collecting or the pumping chambers of the heart that shouldn’t be there.

Unfortunately not all congenital heart problems are picked up by scans done during pregnancy but most of the missed major ones will become obvious in the first day or two of life.  A school aged child who is growing well with normal oxygen saturations and has an incidental finding of a quiet heart murmur, especially if it changes in character with the child’s position, is unlikely to have much seriously wrong with them.

http://kidshealth.org/parent/medical/heart/murmurs.html# is one of the top American sites on children’s health aimed at the general public.  It provides balanced information in clear English about heart murmurs for parents who are worried that their GP or paediatrician has picked up a heart murmur when examining their child.

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