d)Calcified mitral leaflet
ANS IS A i.e mitral stenosis
The intensity of the first heart sound (S1) is influenced by (1) the position of the mitral leaflets at the onset of ventricular systole:- [The loud S1 in mitralstenosis usually signifies that the valve is pliable and that it remains open at the onset of isovolumetric contraction because of the elevated left atrial pressure.]; if AV flow is increased because of high cardiac output or prolonged because of mitral stenosis.;S1 is louder if diastole is shortened because of tachycardia ,or if atrial contraction precedes ventricular contraction by an unusually short interval, reflected in a short PR interval
(2) the rate of rise of the left ventricular pressure pulse;A soft S1may be due to slow rise of the left ventricular pressure pulse AND a long PR interval,
In short PR interval and Tachycardia both position and rate of rise of left ventricular pressure pulse increases the First heard sound loudness
(3) the presence or absence of structural disease of the mitral valve; a Soft S1 may be due to imperfect closure due to reduced valve substance, as in mitral regurgitation.S1 is also soft when the anterior mitral leaflet is immobile because of rigidity and calcification, even in the presence of predominant mitral stenosis.
(4) the amount of tissue, air, or fluid between the heart and the stethoscope.:-A soft S1may be due to poor conduction of sound through the chest wall.