Loud S1 in Mitral stenosis is caused by:

Answer is A (Prolonged flow through mitral valve) Loud SI in mitral stenosis results from prolonged AV flow through the mitral vain `S1 is louder i fAV flow is prolonged because of mitral stenosis' -- Harrison Reduced mobility of valve (Immobility, calcification), and Prolonged PR interval (1st degree block) are all causes of soft S1. Note: First degree block is characterized by prolonged PR interval.