The location of the perimembranous ventricular septal defect is located at the root of the tricuspid septal valve, and the septal plane where the defect is located forms an angle with the tricuspid septal valve. Due to the septal defect, blood is shunted from the left ventricle to the right ventricle through the membranous septal defect for a long time, and the blood flow is shocked in the above mentioned angle to form turbulence, which leads to the hyperplasia and expansion of the endomyocardial tissue under the tricuspid septal valve, and the hyperplastic endomyocardial tissue covers part of the right ventricular surface of the septal defect or even completely, at this time, this part of the hyperplastic endomyocardial tissue covering the septal defect is still subject to the left-to-right shunt At this time, the hyperplastic endocardial tissue covering the ventricular septal defect is still subject to the impact of the left-to-right shunt, resulting in this part of the tissue growing like a balloon, expanding to the right and forming a tumor-like structure. The formation of the membranous tumor is beneficial to reduce the shunt area of the ventricular septal defect, alleviate clinical symptoms, and delay the development of pulmonary hypertension, but excessive tumor formation may lead to right ventricular outflow tract obstruction or tricuspid valve dysfunction.