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Parents are sometimes shocked to hear the doctor say, "I hear a little heart murmur," while he examines their child. The pronouncement sounds so ominous; I don't think any parent can recieve this news with anything but some trepidation. However, it is actually rare that they have anything to fear, as the discussion of functional heart murmurs makes plain. I have included in the /EncyMaster/clopedia very brief discussions of some of the more common specific heart lesions which cause these murmurs.
I enter this discussion with some trepidation, because I am not a cardiologist and there are so many different cardiac lesions possible. This discussion is intended to be very baseline type information only. I will discuss a few of the more common ones briefly in the Encyclopedia, but I leave full discussion of them to your pediatric cardiologist. With the availability of in-office cardiac ultrasonography nowadays, when parents are referred to a pediatric cardiologist they usually leave the first visit with a definitive diagnosis and prognosis and counsel about what to expect. The discussions here are actually aimed at the idly curious or concerned friends or relatives of parents whose child has been diagnosed with a specific cardiac problem.
First a word or two about the normal heart. Ordinarily, the sound of the heart is a steady "lup-dup, lup-dup, lup-dup." with a rising emphasis on the dup sound. These lup-dup sounds, with which everyone is familiar, are simply the closing thumps of the heart valves as blood is pumped in the never-ending cycle of blood flow, fill-eject-refill, through the heart. The first sound is the sound of the inflow valves that fill the ventricles closing with a thump as the main pumping stroke begins; the second sound is the sound of the main outflow valves to the aorta and pulmonary arteries snapping closed at the end of the pumping stroke. The second sound is normally split, that is the aortic and pulmonic valves can be heard closing separately, since the back pressure on the aortic (to the body) valve is considerably higher than that on the pulmonic (to the lungs) valve. So actually,it is more of a "lup - dudup" rythmn.
A heart murmur is an extra sound heard between the lups and dups, that is between the valve sounds. The character of the extra sound can be variously a whoosh, a twang, a rumble, or a high-pitched squeak, among others. Murmurs are diagnosed by their characteristic sounds (frequ/EncyMaster/ and patterns of intensity), by their position in the cycle of the heart beat, and by where they are heard both loudest in the chest and where the sounds can also be heard besides the primary area (for example, if the sound of a murmur "radiates" to the back - that is can also be heard there).
When blood is rushing into the heart as it relaxes to fill we say it is in diastole (die-AS-toe-lee). When the blood is forcibly pumped out of the heart, we say it is in sytole (SIS-toe-lee). Thus murmurs can be either systolic (occur during the pumping stroke) or diastolic (occur during the filling phase).
The fundamental cause of any heart murmur is turbulent blood flow. This may be caused among other things by an abnormal opening between two chambers of the heart (ventricular septal defect, atrial septal defect), by an abnormal heart valve (pulmonic stenosis, mitral valve prolapse, aortic stenosis), abnormalities of the normal internal anatomy of the heart chambers (infundibular stenosis), or by narrowing of a major artery (coarctation of the aorta).
Heart murmurs may be benign (functional), or they may be pathologic. Benign or functional heart murmurs are usually identified easily because of their distinct character. They are short, often twangy in sound, with an ejection type pattern of crescendo-decrescendo (waxing and waning) intensity. There is an audible gap between the "lup" and the beginning of the murmur, and between the end of the murmur sound and the "dudup." Pathologic murmurs are basically those which aren't benign; they are associated with actual malformations of the heart, usually congenital.