Overview
The first heart sound (S1) indicates closure of the mitral and tricuspid valves.
S1 is normally heard best over the apex.
Loud S1
Listen For
- Increased intensity of the first heart sound.
Causes of a Loud S1
- Mitral stenosis
- Hyperdynamic circulation - exercise, infection, hyperthyroidism, pregnancy
Soft S1
Listen For
- Reduction in intensity of the first heart sound.
Causes of a Soft S1
- Mitral regurgitation
- Ventricular septal defect
- First degree heart block
- Left bundle branch block
- Myocardial depression
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