Heart murmur overview
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Heart murmur overview On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
A cardiac murmur is an abnormal heart sound produced as a result of turbulent blood flow, which is sufficient to produce audible noise, defined as a relatively prolonged series of auditory vibrations of varying intensity (loudness), frequency (pitch), quality, configuration, and duration. [1] Most authorities now agree that turbulence is the prime factor responsible for most murmurs. Turbulence occurs when blood velocity becomes critically high because of high flow, flow through an irregular or narrow area, or a combination of both. Murmurs are not usually part of the normal cardiac physiology and thus warrant further investigations. However, they sometimes result from harmless flow characteristics of no clinical significance.
Leatham has attributed the production of murmurs to three main factors: High flow rate through normal or abnormal orifices, forward flow through a constricted or irregular orifice or into a dilated vessel or chamber, and backward or regurgitant flow through an incompetent valve, septal defect, or patent ductus arteriosus. Frequently, a combination of these factors is operative.
Laboratory Findings
In a patient with a heart murmur, a complete blood count (CBC) may be useful in evaluating anemia as a contributing condition, thyroid function tests may be checked to rule out hyperthyroidism, and blood cultures may be helpful in excluding endocarditis.
Echocardiography
An echocardiogram is the diagnostic study of choice in a patient with a murmur, and should be obtained in asymptomatic patients with diastolic murmurs, continuous murmurs, holo-systolic murmurs, late systolic murmurs, murmurs associated with ejection clicks or murmurs that radiate to the neck or back as well as a grade 3 or louder midpeaking systolic murmur. An echocardiogram should also be obtained in patients with evidence of myocardial infarction or ischemia, heart failure, congenital heart disease, syncope, endocarditis. Echocardiographic evaluation is not recommended in some murmurs, such as a grade 2 or softer mid-systolic murmur, which can be an "innocent", "benign" or "functional".
References
- ↑ Soffer A, Feinstein A, Luisada AA, et al. Glossary of cardiologic terms related to physical diagnosis and history. Am J Cardiol 1967; 20: 285–86