The main symptoms of a ventricular septal defect depend on the size of the defect and the age of the patient. Generally, smaller ventricular septal defects, such as those measuring only one to two millimeters, result in very little shunting from the left ventricular system to the right ventricular system. This is akin to a tiny amount of air seeping through a crack in a window or door. In such cases, the patient typically does not exhibit noticeable symptoms. However, if the defect is larger, over five millimeters, a significant amount of blood passes from the left ventricular system into the right ventricular system, which can cause substantial congestion in the right or both lungs of the right ventricular system, or lead to recurrent respiratory infections and congestive heart failure. The affected individual may show disinterest in eating, feeding difficulties, and delayed development. As the patient grows older, they may exhibit reduced activity endurance, fatigue or palpitations, and shortness of breath. Gradually, cyanosis and right heart failure may develop. Additionally, patients are at risk of developing infective endocarditis, fever without symptoms, and recurring fever.