heart sounds
Reading File
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heart sounds S1 S2 S3 S4 murmurs clinical auscultation authoritative
Reading File
Heart sounds are vibrations produced mainly by valve closure and blood flow, heard on auscultation.
| Sound | Timing and mechanism | Usual meaning |
|---|---|---|
| S1 | “Lub.” Closure of the mitral and tricuspid valves at the start of ventricular systole. | Best heard at the apex. Marks the beginning of systole. |
| S2 | “Dub.” Closure of the aortic and pulmonary valves at the end of systole. | Best heard at the base. Marks the end of systole. It normally splits slightly during inspiration because pulmonic closure is delayed. |
| S3 | Low-pitched sound just after S2, during rapid ventricular filling: “Kentucky” rhythm. | Can be normal in children, young adults, and pregnancy. In older adults, often suggests volume overload or heart failure. |
| S4 | Low-pitched sound just before S1, from atrial contraction into a stiff ventricle: “Tennessee” rhythm. | Usually abnormal, such as with hypertension, left-ventricular hypertrophy, aortic stenosis, or ischemia. It is absent in atrial fibrillation. |
Where to listen
- Aortic area: right 2nd intercostal space, sternal edge
- Pulmonic area: left 2nd intercostal space, sternal edge
- Tricuspid area: left lower sternal border
- Mitral area (apex): left 5th intercostal space, midclavicular line
Use the diaphragm for higher-pitched sounds such as S1, S2, and most murmurs. Use the bell, lightly applied at the apex or left lower sternal border, for low-pitched S3, S4, and mitral stenosis.
Murmurs are prolonged sounds caused by turbulent blood flow. A murmur during diastole is generally pathologic; systolic murmurs may be innocent or pathologic. MSD’s auscultation guide also provides example recordings and explains abnormal splitting of S2.
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