First heart sound

Left ventricular filling decreases during mitral stenosis, and the mitral valve position is lower in the late diastole. Second, due to the decrease in left ventricular blood volume, the systole shortens accordingly. At this time, the pressure in the left ventricle rises rapidly, resulting in a low mitral valve. Suddenly nervous and closed, resulting in a high-profile and crisp first heart sound that sounds like a flapping sound, often called a flapping first heart sound. During complete atrioventricular block, the atrial and ventricular beats are irrelevant, forming an atrioventricular separation phenomenon. When the atrium and ventricle are contracted at the same time, the first heart sound is extremely loud, which is usually visually called "cannon sound" ".