First hea sound is soft in all except
Ref Harrison 19 th ed pg 1447 S1 becomes softer in the later stages of MS when the leaflets are rigid and calcified, after exposure to b-adrenergic receptor blockers, with long PR intervals, and with left ventricular contractile dysfunc- tion. The intensity of hea sounds, however, can be reduced by any process that increases the distance between the stethoscope and the responsible cardiac event, including mechanical ventilation, obstruc- tive lung disease, obesity, pneumothorax, and a pericardial effusion.
General anatomy
Sho PR interval
Ventricular septal defect
Mitral regurgitation
Calcified Valve
Sho PR interval