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A heart murmur is a blowing, whooshing, or rasping sound heard during a heartbeat. The sound is caused by turbulent (rough) blood flow through the heart valves or near the heart. (source)
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A murmur is a series of vibrations of variable duration, audible with a stethoscope at the chest wall, that emanates from the heart or great vessels. A systolic murmur is a murmur that begins during or after the first heart sound and ends before or during the second heart sound. (source) A diastolic murmur is a sound of some duration occurring during diastole. (source)
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(Wikipedia) Heart murmurs may have a distinct pitch, duration and timing. Murmurs have seven main characteristics. These include timing, shape, location, radiation, intensity, pitch and quality
- Timing refers to whether the murmur is a
- systolic murmur
- diastolic murmur. Diastolic murmurs are usually abnormal, and may be early, mid or late diastolic (source)
- continuous murmur
- Shape refers to the intensity over time. Murmurs can be crescendo, decrescendo or crescendo-decrescendo
- Crescendo murmurs increase in intensity over time
- Decrescendo murmurs decrease in intensity over time
- Crescendo-decrescendo murmurs have both shapes over time, resembling a diamond or kite shape
- Location refers to where the heart murmur is usually heard best. There are four places on the anterior chest wall to listen for heart murmurs. Each location roughly corresponds to a specific part of the heart.
Region Location Heart Valve Association Aortic 2nd right intercostal space Aortic valve Pulmonic 2nd left intercostal spaces Pulmonic valve Tricuspid 4th left intercostal space Tricuspid valve Mitral 5th left mid-clavicular intercostal space Mitral valve - Radiation refers to where the sound of the murmur travels.
- Intensity refers to the loudness of the murmur with grades according to the Levine scale, from 1 to 6
Levine scale Murmur Description 1 only audible on listening carefully for some time 2 faint but immediately audible on placing the stethoscope on the chest 3 loud, readily audible but with no palpable thrill 4 loud with a palpable thrill 5 loud with a palpable thrill, audible with only the rim of the stethoscope touching the chest 6 loud with a palpable thrill, audible with the stethoscope not touching the chest but lifted just off it - Pitch may be
- low
- medium
- high This depends on whether auscultation is best with the bell or diaphragm of a stethoscope.
- Quality refers to unusual characteristics of a murmur. For example
- blowing
- harsh
- rumbling
- musical
- Timing refers to whether the murmur is a
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Heart sounds usually has frequency lower than 500 Hz (mostly lower than 300 Hz) (inferred from source Figure 2). frequency of heart sounds is low in range between 20 and 150 Hz.
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Instantaneous dominant heart sound frequencies ranged from 130 to 410 Hz (mean ± standard deviation 282 ± 70 Hz). Peak murmur frequencies ranged from 200 to 410 Hz (308 ± 70 Hz) (source)
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innocent murmurs had lower frequencies (below 200 Hz) and a frequency spectrum with a more harmonic structure than pathological cases (source). Table 4 is very important and copied as follows
Group Amplitude (%) Low freq limit (Hz) High freq limit (Hz) Vibratory 23 ± 9 72 ± 15 161 ± 22 Ejection 20 ± 9 60 ± 9 142 ± 51 Pathological 30 ± 20 52 ± 19 299 ± 133 p-value 0.013 < 0.001 < 0.001 -
the principal frequencies of heart sounds and murmurs are at the lower end of this range, from 20 to 500 Hz; The murmur containing the highest frequency sound is aortic regurgitation, whose dominant frequencies are approximately 400 Hz. The principal frequencies of other sounds and murmurs are between 100 and 400 Hz (source1, source2)