Paradoxical embolism
Paradoxical embolism, also known as “crossed embolism”, is the transfer of a blood clot (embolus) from the venous to the arterial part of the bloodstream. The reason for this is a defect in the area of the heart septum, usually caused by an unclosed Foramen ovale. When the foramen ovale is closed, the lung takes over the function of filtering out possible thrombi.
As a rule, hardly any blood passes from the right atrium to the left atrium after birth by opening the pulmonary circulation, even with an open foramen ovale. The reason for this is a highly regulated pressure gradient within the heart, which dictates the direction of blood flow. If this pressure gradient changes when the foramen ovale is open, excessive overflow through the open atrial septum can occur.
This may also cause a clot to pass over the atrial septum and enter the arterial circulatory system directly. If the blood vessels are blocked, the clot may become occluded, resulting in symptomatic symptoms. The change in pressure can have many different causes, such as coughing, sneezing, pressing or a pulmonary embolism.
What role does the Foramen ovale play in the stroke?
One of many causes of a stroke can be an unclosed Foramen ovale. This form of stroke is called cryptogenic stroke. Cryptogenic in this respect only means that none of the classic causes caused the stroke.
In an unclosed Foramen ovale, small venous thrombi from the right atrium can directly enter the left atrium. This ensures a quick and easy transfer into the large body circulation. The pulmonary circulation is simply left out – the thrombus is led from the right to the left atrium and from there directly to the left ventricle and the aorta, which means that such a thrombus can also reach the brain correspondingly quickly.
How to close the Foramen ovale?
The Foramen ovale can be closed in adults by minimally invasive surgery. A small incision is made in the groin, allowing a tube system (catheter) to be inserted and advanced through the blood vessels to the heart. A small implant in the form of a small umbrella can then be inserted into the open foramen ovale.
The umbrella consists of two parts, which are made of a soft wire mesh. One of the parts is placed on the opening of the Foramen ovale in the right atrium, while the other part is placed on the opening of the Foramen ovale in the left atrium. The two parts are connected by a small bar through the atrial septum opening.
In the course of a few days, the wire meshes grow into the heart wall, which leads to the final closure of the Foramen ovale. The procedure takes between one and two hours and is performed in a cardiac catheterization laboratory. The inserted implant can remain inserted in the heart for a lifetime, provided that no symptoms occur. However, such a procedure is not universally recommended. Depending on the size of the oval foramen and possible existing complaints, a drug intervention by blood thinning may be sufficient or even no treatment at all may be necessary.