Heart murmur overview
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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] Murmurs are not characteristic of normal cardiac physiology and may warrant further evaluation, particularly if they occur during diastole. However, murmurs are sometime "innocent" or benign if they are only due to increased flow across a normal heart structure.
Pathophysiology
Turbulent flow is responsible for most murmurs. Turbulent flow occurs when the velocity of blood flow becomes critically high because of a high volume of flow, the flow goes through an irregular or narrow area, or a combination of the two.
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.
Causes
Diastolic Heart Murmurs
- Aortic insufficiency
- Anomalous pulmonary venous drainage with left-to-right shunt
- Atrial myxoma
- Atrial septal defect (ASD) with left-to-right shunt
- Austin Flint murmur
- Bronchial collaterals
- Carey-Coombs murmur
- Cervical venous hum
- Coarctation of the aorta
- Coronary or pulmonary arteriovenous fistula
- Hepatic venous hum
- Mammary souffle
- Mitral Stenosis
- Patent Ductus Arteriosus (PDA)
- Pericardial knock
- Pulmonary artery branch stenosis
- Pulmonary insufficiency
- Tricuspid Stenosis
Systolic Heart Murmurs
- Aortic Sclerosis
- Aortic Stenosis
- Atrial septal defect
- Bicuspid aortic valve
- Cervical venous hum
- Coarctation of the aorta
- Coronary/pulmonary arteriovenous fistula
- Endocarditis
- Hepatic venous hum
- Hyperthyroidism
- Innocent systolic murmur
- Left ventricular outflow tract obstruction
- Mammary souffle
- Mitral insufficiency
- Mitral valve prolapse
- Papillary muscle dysfunction
- Patent Ductus Arteriosus (PDA)
- Pericardial friction rubs
- Peripheral pulmonary artery stenosis
- Prosthetic valve noises
- Pulmonary artery stenosis
- Pulmonic outflow obstruction
- Still's murmur
- Tricuspid insufficiency
- Ventricular septal defect
Continuous Murmurs
- Aortic stenosis / aortic insufficiency
- Pericardial friction rub
- Pulmonary arteriovenous fistula
- Venous hum
- Mammary souffle
- Aortic coarctation
- Mediastinal air dissection
- Patent ductus arteriosus
- Ruptured sinus of Valsalva
- Coronary artery fistula
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