Heart Sounds and Murmurs
Murmurs are cause by turbulent blood flow. They are described in relation to the following heart sounds:
S1: Caused by closing of the mitral and tricuspid valves
S2: Caused by closing of aortic and pulmonary valves
While auscultating, the radial or brachial pulse should be palpated as they indicate systole. Any murmur between S1 and S2 is named systolic as it occurs during the systolic phase of cardiac contraction. Similarly, diastolic murmurs occur between S2 and S1 when the myocardial muscle relaxes.
Auscultation should be carried out in a systematic manner with the patient supine at a 30⁰ angle. Note that the diaphragm of the stethoscope should be used initially before repeating again with the bell to detect low-pitched murmurs.
The following areas should be auscultated and correspond to where murmurs from the respective valve abnormalities could be heard loudest.
Mitral area: 5th intercostal space, mid-clavicular line (apex)
Tricuspid area: Left sternal border at 5th intercostal space
Pulmonary area: Left sternal border at 2nd intercostal space
Aortic area: Right sternal border at 2nd intercostal space
To fully appreciate the extent of a murmur, it is important to also check for the presence of thrills at the above locations, as well auscultate the carotid arteries and axilla for any radiation of murmurs.
The following manoeuvres can be used accentuate specific murmurs.
- Expiration: Left-sided murmurs (aortic, mitral)
- Inspiration: Right-sided murmurs (pulmonary, tricuspid)
- Valsalva: Hypertrophic obstructive cardiomyopathy, mitral valve prolapse
- Squatting: Ventricular septal defect, aortic regurgitation, mitral regurgitation
- Leaning forwards: Aortic regurgitation
- Left lateral decubitus: Mitral stenosis
Murmurs are graded on a 6-point Levine scale based on their loudness and presence of a palpable thrill. It is important to note that the loudness of a murmur does not always correlate with the degree of valvular abnormality. A palpable thrill indicates that a murmurs should graded as at least a 4 out of 6.
No thrill present:
1/6: Faint murmur
2/6: Faint murmur but readily detectable
3/6: Loud murmur without a thrill
Thrill present (palpable vibration over a valve region):
4/6: Murmur present along with a thrill
5/6: Murmur audible when edge of stethoscope is on the chest
6/6: Murmur audible with stethoscope off the chest