The most common cause of mitral stenosis is valvular damage caused by rheumatic heart disease. Depending on the degree of valvular damage, the diseased valve often co - exists with insufficiency, resulting in different murmurs. Generally, it is often manifested as an accentuated first heart sound, which is like a tapping sound. A localized, low - pitched, rumbling mid - to - late diastolic murmur can be heard in the apical area. The murmur is crescendo and has presystolic accentuation. It is most obvious in the left lateral decubitus position, especially after a little physical activity and then turning to the left lateral decubitus position, and may be accompanied by diastolic tremors. In the funnel - shaped mitral valve, the valve opening is rigid and funnel - shaped, and the valve loses its elasticity. The first heart sound in the apical area is weakened and is often accompanied by a systolic murmur. At the second and third intercostal spaces on the left border of the chest, an ejection sound can be heard immediately after the first heart sound. It is loudest on expiration and may be reduced or disappear on inspiration.