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cardiac murmur[′kärd·ē‚ak ¦mər·mər]
(also heart murmur), a sound accompanying heart function and occurring in the pauses between heart sounds. Cardiac murmurs are longer aperiodic sound vibrations than heart sounds. They are detected by auscultation and phonocardiography.
There are organic and functional cardiac murmurs. Organic heart murmurs are primarily caused by blood passing through apertures that have become narrowed as a result of pathological processes. The deformation and adhesion of valves result from inflammatory diseases (most often rheumatic fever) or sclerotic processes that are congenital anomalies of the heart and major vessels. Strictures of the normal path of blood flow occur; such strictures include cardiac, aortic, and pulmonary stenoses. Reverse blood flow through a narrow slit in the heart results from abnormal connections between the chambers of the heart or from cusps that are prevented from closing properly (valvular insufficiency). Knowledge of the existence of an organic cardiac murmur is often very important in the diagnosis of heart disease.
Functional cardiac murmurs may result from an acceleration of blood flow or from differences in papillary muscular tension. Such murmurs are found in persons suffering from certain diseases (for example, anemia) and in healthy children, young women, and, often, athletes. Functional cardiac murmurs may be variants in the normal sound picture of heart function.
I. M. KAEVITSER