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The interventricular septum or ventricular septum refers to an important dividing wall in the heart. This wall separates the ventricles, which are the lower two heart chambers and the major pumping chambers of the heart. In most circumstances, it is exceptionally important that full separation is achieved and each ventricle functions without any type of blood communication with the other. The interventricular septum achieves this, except when defects exist in it or certain cardiac diseases affect it.
In the normal heart, right chambers are divided from left chambers by a septum. A small communication, called the foramen ovale, is left open between the atria, and this usually closes in the first year of life. A similar opening should not exist in the interventricular septum. When it is formed in the first few months of life, the wall or septum is meant to be closed.
As the interventricular septum develops, it actually has two discrete portions, though the wall is continuous. The top portion is called membranous or perimembranous, and the bottom part is called muscular. Sometimes, as the heart is forming, an error occurs in the building of the septal wall, and instead of the desired closure between the right and left ventricle there are communications between the two chambers via holes. These most often occur in the perimembranous portion, but about a fourth of them may present in the muscular interventricular septum portion too. Both are called ventricular septal defects or VSDs.
While some types of VSDs are small and don’t require medical intervention, large holes or multiple holes in the interventricular septum can be extremely problematic. One issue that may occur is that they can cause blood from the left ventricle, which is about to be pumped to the body, to seep into the right ventricle, and this can increase pulmonary pressure, and ultimately cause issues like left heart failure too. Large VSDs are usually fairly easy to diagnose become of discernible heart murmurs, but little ones may be harder to catch.
Oddly enough, sometimes the interventricular septum actually interferes with heart function if the heart has several prominent defects. If there are errors with the heart valves, very small ventricles or other issues, a big VSD can allow for needed blood-mixing, and may actually help promote survival until surgery is performed. Whether or not a VSD is closed during surgery on complex defects depends on surgery type and ability to repair all defects.
Another problem may occur in the interventricular septum, and it has nothing to do with being born with birth defects. Though rare, during some heart attacks, the septum may be damaged or even have a hole in it afterward. It is usually vital to address this heart attack VSD as quickly as possible to restore normal heart health.