Simple congenital heart defects, such as perimembranous defects, generally are not particularly severe. However, there are several scenarios to consider:

The first scenario involves a large defect that typical occluders cannot address; in such cases, surgical intervention is required. This type of defect is generally considered severe.

Another scenario is when a cardiac defect has been present for an extended period, leading to repeated shortness of breath, heart failure, cardiac enlargement, and even pulmonary arterial hypertension. This situation would be considered a severe ventricular septal defect, caused by the failure to treat the membranous part of the septal defect in time.

Thus, the majority of ventricular septal defects are not very severe in the early stages. They become serious if the defect is too large or if there is coexistence with other defects, such as an overriding aorta or poorly developed pulmonary artery, among other complex congenital heart diseases. Regardless, patients with perimembranous congenital heart defects should undergo surgical treatment early to avoid missing the opportunity for surgery.