Heart septal defect

The atria and chambers of the right and left heart are each separated by a wall. A hole in these partitions can cause serious damage to the cardiovascular function. What exactly is a heart septum defect, how to recognize it and what to do in such a case, you can read here.

What is a heart septum defect?

The septum, which can reach several millimeters thick, separates the heart cavities of the right heart from those of the left. Right atrium and right ventricle are part of the so-called low-pressure system in the circulation, flows through the oxygen-poor, venous blood to the heart and is pumped after passage of atrium and chamber into the pulmonary circulation.

After being saturated with oxygen in the lungs, the now oxygen-rich, bright red blood flows into the high-pressure arterial system fed by the left heart. Consequently, the cardiac dividing walls also constitute interfaces between two systems with different pressure ratios. One fact that is important in understanding the sequelae of septal defects: cardiac septal defects are nothing more than different sized holes between the atria or chambers, the short circuits for high pressure blood flow and low pressure system create.

Causes of heart septum defects

In the vast majority of cases, the heart septum defects are based on genetic causes. These genetic defects lead during the early developmental period of the unborn child in the womb to a variety of malformations of the heart, sometimes also to heart septum defects. In rare cases, septal defects are acquired only in the course of life, usually a major heart attack is responsible for the defect.

Forms of the heart septum defect

Heart septal defects appear as either isolated heart defects or in conjunction with other complex malformations of the heart and large, near-the-heart vessels. Depending on the localization one differentiates

  • Defects of the atrial septum (ASD = atrial septum defect); the third most common congenital heart defect in adolescents and adults
  • Defects of the ventricular septum

atrial septal defect

Due to the higher pressure conditions in the left atrium, a hole in the atrial septum causes blood to flow directly from the left atrium into the right atrium - the amount depends, among other things, on the size of the defect. Due to this short circuit, part of the already oxygen-saturated blood flows directly back to the right heart and thus to the small circulation without being able to contribute to the blood circulation of the organs in the large circulation. This means above all, that in the pulmonary circulation by the increased blood volume, a higher pressure.

Ultimately, the size of the septal defect is decisive for the resulting burden on the small circulation with disproportionately high blood. Especially small holes of the heart septum can last a lifetime without causing any problems. In the case of major defects, increased stress on the right heart and the pulmonary circulation, which must be able to cope with the additional blood flow via the septal defect, must be expected as early as childhood. In the longer term, heart muscle weakness in the right, overstretched ventricle, and pulmonary hypertension may be on the increase, further aggravating stress on the right heart.


The differences in pressure between the left and right ventricles are even more pronounced than at the atrial level, so that a well-developed ventricular septum causes an even greater blood flow from left to right and an even greater load on the right heart than in the atrial septal defect.

With particularly large septum defects, a shunt reversal can occur. The resistance in the small circulation and the pressure in the right heart increase so much by the constant additional load, that the pressure in the right ultimately exceeds the pressure in the left heart. Under these conditions, the bloodstream changes direction and now flows from right to left. This means that it is only insufficiently enriched with oxygen.

Once shunt reversal has taken place, it marks an extremely unfavorable turning point in the course of the disease, as heart surgery will no longer have any chance of success from this point on.

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