This refers to the possibility of “leakage” after surgery for ventricular septal defects. For septal defects less than 5 mm in diameter, direct suturing is usually used. For larger defects, a patch is used, either a pericardial patch or a polyester patch, depending on age and weight. According to the literature, the incidence of re-leakage of the patched “hole” is about 5%. The main reasons for this are as follows: (1) Multiple ventricular septal defects are often combined with several defects, and sometimes it is difficult to completely expose the defect during surgery, and only part of the defect is sutured during surgery, and some of it remains. (2) Suture avulsion has a higher incidence in repairing large ventricular septal defects. In order to prevent the normal tissues around the defect, especially the conduction system of the heart, sutures can only be placed in the superficial layer of the defect during repair, and after the heart resumes beating with the increase of pressure in the heart cavity, some of the sutures will be torn off, resulting in residual shunt. (3) Incomplete repair mostly occurs in small septal defects, especially in patients with pseudoventricular septal tumor formation, where the opening appears small but the base is large, and residual shunts often occur after surgery if only the opening is sutured closed. (4) Infection occurs after surgery, such as bacterial endocarditis, and once infection occurs around the patch after surgery, the sutures often tear off and cause a partial residual shunt. The clinical manifestations of residual shunts include increased heart rate and change in the nature of murmur. The diagnosis is confirmed by ultrasound or cardiac catheterization. Small residual shunts (<3mm) generally do not require surgical management and will mostly close spontaneously. For residual defects with larger shunts, reoperation is often required. Trivia: What is meant by a pseudoventricular septal tumor? It refers to a septal defect with a large opening. With the continuous impingement of blood flow, the fibrous tissue at the edge of the defect proliferates and forms a tumor-like protrusion, and the opening looks small but is actually larger at the base.