Patent Foramen Ovale (PFO) is a communication that exists between the septum that divides the two atria of the heart.
This PFO is usually sealed by a membrane, but a failure during the embryological period can cause it not to be hermetically sealed and remain open. This circumstance occurs in approximately 25-27% of the population, and usually does not cause problems, since the pressure in the left atrium is usually higher than in the right atrium, which pushes the PFO membrane to the right, and there is no passage of blood from the right side of the heart (poorly oxygenated) to the left side. Mixing of right-sided (venous) and left-sided (arterial) blood can cause problems.
The causes that increase the pressure on the right side are Valsalva maneuvers, which means that the intrathoracic pressure increases (lifting heavy weights, sustained coughing, etc.).
- When the PFO is closed, the passage of a small thrombus (generally coming from the lower limbs), migrate to the lung, which is a large reservoir that admits these elements, without major symptoms.
- But when the pressure increases on the right side, for any reason, and the PFO membrane is open, a small thrombus can pass from the right to the left side and migrate to the carotid arteries, producing a stroke.
- A circumstance that is very prone to these accidents is diving at great depth with compressed air. If correct decompression is not performed, the nitrogen accumulated in the tissues, which diffuses very slowly, migrates in large bubbles into the venous system. Since during diving several maneuvers are performed that increase the right pressure (Valsalva), if you also have the misfortune of having a permeable PFO, it is easy to have an Ictus.
- Therefore, before diving, for safety reasons, an echocardiogram should be performed and, if there is PFO, another test called Transesophageal Echocardiogram with sonicated contrast should be performed to determine if there is a right-left passage, and if it is in quantity > 15-20 microbubbles. In that case, it should be advised to limit diving to shallow depths and without requiring decompression or to close the PFO definitively.
And what does one do if there is in any case a PFO with a right-to-left shunt?
There has been a lot of discussion. There are anatomical variables that favor the appearance of stroke (PFO size, number of bubble passage, exaggerated growth of the Eustachian Valve (intracardiac structure that facilitates the passage of venous blood to the left atrium, in case of PFO).
How and when to seal the PFO
In any case, in the case of a young person -whether a diver or not- who presents a cryptogenic stroke (one that occurs after excluding any cardiac, neurological or hematological cause) that may favor it, the opinion is to close it percutaneously. This is done by cardiac catheterization and is closed by implanting a device in the form of a diabolo, which closes the PFO.
However, although there are minor controversies about this type of procedure, it is standard practice in most of Western Europe and Anglo-Saxon countries.
Consult a cardiologist for more information.