Mitral valve insufficiency leads to left ventricular hypertrophy. This occurs because when the mitral valve does not close fully, the contraction of the ventricles often causes the blood in the left ventricle to flow back into the left atrium, resulting in a significant increase in the blood volume of the left atrium. When the ventricles relax the next time, the left ventricle receives a large amount of blood from the left atrium, as well as the remaining original blood. This causes a significant increase in the capacity and load of the left ventricle, and over time leads to enlargement and hypertrophy of the left ventricle. This condition eventually leads to the appearance of symptoms of heart failure, causing the patient to repeatedly experience difficulty in breathing.