A heart murmur is an abnormal or extra heart sound caused by a malfunctioning heart valve. The function
of heart valves is to prevent backflow of blood, and when a valve does not close properly, blood will regurgitate (go backward), creating turbulence that may be heard with a stethoscope.
Rheumatic heart disease is a now uncommon complication of a streptococcal infection. In rheumatic
fever, the heart valves are damaged by an abnormal response by the immune system. Erosion of the valves makes them “leaky” and inefficient, and a murmur of back-flowing blood will be heard. Mitral valve regurgitation, for example, will be heard as a systolic murmur, because this valve is meant to close and prevent backflow during ventricular systole.
Some valve defects involve a narrowing (stenosis) and are congenital; that is, the child is born with an abnormally narrow valve. In aortic stenosis, for example, blood cannot easily pass from the left ventricle to the aorta. The ventricle must then work harder to pump blood through the narrow valve to the arteries, and the turbulence created is also heard
as a systolic murmur.
Children sometimes have heart murmurs that are called “functional” because no structural cause can be found. These murmurs usually disappear with no adverse effects on the child.
Sunday, October 26, 2008
