Patent Foramen Ovale
What is a Patent Foramen Ovale ?
Patent Foramen Ovale or PFO is a structure present in all fetuses. It allows oxygen carrying blood from mother via umbilicus to reach the left side of the heart so that the nutrition from the mother can reach the fetuses’ brain. (See Fetal Circulation for further details)
Is it normal to have a PFO ?
Yes. In 75% of the population the PFO closes some time after birth. In the rest of population, the PFO does not close. It then allows some blood to come over from left side to the right and this has no side effect. This amount of blood can travel from left side to right and does not have any effect.
How many percent people have a PFO ?
25% of the world population has a PFO.
When is a PFO abnormal ?
When a PFO allows blood to travel from Right atrium to Left atrium, then it is considered dangerous. This will allow blue blood to enter the red blood circulation. With this happening, if a clot has formed in the blue (venous) side then, it could reach the right atrium and from there cross over to the left atrium. Such a clot could result in a stroke. This is the true danger of the PFO when there is Right to Left Shunt.
What are the problems that can arise from a PFO ?
If a clot as described above reaches the left aside of the heart it usually ends up in the brain resulting in STROKE. This implies that PFO can be a cause of Stroke. In such a situation, PFO can result in recurrent stroke each time there is a clot in the venous system it will reach the left side of the heart.
Why can’t a clot in the right side of the heart result in a Stroke if there is no PFO ?
The right and the left sides of the heart do not communicate with each other unless there is a hole (like a PFO) which would allow right side blood to enter the left side. If there is a clot and there is no PFO, then the clot would enter the right heart and from there the filter system of the lung. In such cases clot would get deposited in the lung, which, with small clot may not be a significant problem.
What is the treatment of these problems ?
The treatment of this problem is PRESUMABLY closure of the PFO. If PFO is closed, the clot cannot enter the left side of the heart and would end up being trapped and filtered out in the lungs.
Have studies confirmed that closure of a PFO will decrease the incidence of strokes ?
There are several ongoing trials. As logical as it may sound, this has not been confirmed by research. The trials being conducted are looking at proof that this form of treatment is better than medical treatment and that truly the risk of recurrent strokes will come down after device closure of the PFO.
How is a PFO closed ?
The PFO used to be closed by surgery, which in itself increases the risk for clots. So, this used to be done very infrequently. Now, PFO closures are done by Devices which is a percutaneous procedure which does not require any surgery and a short hospital stay. The device is inserted from the groin via a catheter (a long thin tube like an extended ball pen refill). The device is made of Nitinol and can be folded and taken in. The procedure itself is not as challenging as several others cardiologists may be performing; the real question doctors want to know is whether this will benefit the patients or not.
What is required to close a PFO ?
The current indication to close a PFO is when one stroke has happened and patient needs to be sure that no more clots will travel to the left heart.
What are the other options apart from Device Closure ?
The currently available other option is that the patient may stay on anticoagulation which allows the blood to stay thin and not to clot. This is also a good way of preventing clots. The clot does not form at all with this treatment, unlike with PFO device closure where the clot may form but has no chance of entering the left heart.
What are the Advantages of a PFO closure ?
The advantage is to remove one element or cause or a potential right to left shunt totally (if the device will close the hole completely).
What are the disadvantages of PFO closure ?
The device is made of metal and may itself be a source of clots.
What is the proof of PFO closure helping in the recurrence of stroke ?
We do not have absolute proof that closing PFOs will decrease the incidence of strokes or make it close to zero (the chance of a stroke hapenning again).
What is the connection between a PFO and Migraine ?
Only in severe intractable migraine not responding to medical therapy has there been a consideration for closure of PFO.
But why migraine ?
Well, the incidence of PFO in patients with migraine is higher than in general population. In addition, there were reports that when PFO or ASD was closed for other reasons in patients with incidental migraine, the migraine went away. This initiated a lot of research which is ongoing relating PFO closure to Migraine.