loud first (1st) heart sound
A loud first heart sound occurs when the leaflets are wide open at the end of ventricular diastole and shut forcefully at the beginning of ventricular systole.
Possible causes of a loud first heart sound include:
- late atrioventricular closure
- this occurs when there is rapid flow at the end of diastole e.g. mitral stenosis, the short diastole of tachycardic states and left to right shunts
- where the P-R interval is less than 0.12 s. This situation results in an opened valve that is not closed at the time of ventricular contraction.
- atrial fibrillation
- short diastole - tachycardia
- atrial premature beat
- mitral stenosis where high left atrial pressure delays mitral valve closure
Last reviewed 01/2018