Definition
A paradoxical embolism has the same basic structure as a normal venous embolism with a special feature or deviation. An embolism is a sudden blockage of a blood vessel by a plug (embolus). This washed up in the bloodstream (via the venous blood).
It usually originates from a leg vein. It is not soluble in the blood and can be liquid, gaseous or solid. In any case, its diameter is larger than the blood vessel where it is stuck, which is why it clogs it.
In a paradoxical embolism, this clot passes from the veins through gaps in the cardiac septum into the left heart. So it is now in the arterial blood vessel. This means that the embolus does not enter the lungs as in a normal embolism, but rather into the arterial system of the body’s circulation.
Causes
The cause of a paradoxical embolism is a clot (embolus). This embolus usually comes from a deep leg vein. Only very rarely does it originate from a superficial leg vein.
The clot detaches from its point of origin and travels through the bloodstream until it clogs a vessel due to its size. Slowed blood circulation is cited as the cause of an embolism. It therefore occurs frequently in bedridden, overweight and old people.
In addition, vascular wall changes such as those caused by smoking, high blood pressure or diabetes can also be a cause. Venous diseases such as varicose veins can also be responsible for a clot. In order for the embolism to become a paradoxical embolism, the clot must pass from the venous blood into the arterial system.
This is caused by defects or openings in the cardiac septum. This means that the blood can flow from the right atrium into the left atrium and into the arterial blood. During fetal development, a hole is made in the cardiac septum, which is essential for the blood circulation of the unborn child.
This circulation differs from that of a born human being, since independent breathing does not yet take place in the abdomen. Shortly after birth or with the first breaths this opening normally closes. If this is not the case, the opening that remains open can be responsible for a paradoxical embolism.
Often, defects of the cardiac septum are congenital. The Foramen ovale (oval hole) is an opening in the cardiac septum between the two atria. It has a door-like structure.
This hole is present during fetal (prenatal) development. After birth, the hole usually begins to close with the first breaths and is completely closed after a few days at the latest. Since a foetus in the abdomen does not yet breathe on its own, the lung is bypassed in the bloodstream.
Gas exchange takes place via the mother and not through the lungs. To bypass the pulmonary circulation, the Forman ovale is necessary. Blood can flow in the heart directly from the right atrium to the left atrium without passing through the lungs.
