The first heart sound is loud in all of the following EXCEPT

 # The first heart sound is loud in all of the following EXCEPT:
 A. Mitral stenosis
B. Short PR interval
C. Tachycardia
D. Mitral valve calcification

The correct answer is D. Mitral valve calcification.

The intensity of the first sound is primarily related to the position of the atrioventricular valves at the onset of ventricular systole.

The first sound is usually louder in subjects with a short PQ interval than in those with a long PQ interval.

Loud first heart sound: is seen in mitral stenosis, left atrial myxoma, conditions that increase myocardial contractility, including hyperadrenergic states (e.g. exercise, anxiety, anemia, fever, pregnancy, and thyrotoxicosis) and in patients with thin chest walls. 

A loud first heart sound is a hallmark of hemodynamically significant mitral stenosis. Mobile but stiff mitral leaflets produce a loud S1 unless the leaflets are heavily calcified. The main reason for the increase in the intensity of S1 in these conditions is the increased rate of pressure development in the ventricles. 

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