<prompt> First hea sound is soft in all exceptSho PR intervalVentricular septal defectMitral regurgitationCalcified Valve  <response>: 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. 