PFO and ASD Percutaneous Closure

What is a PFO?

A patent foramen ovale (PFO) is a persistent opening between the left and right atrium (top chambers) in the heart. Prior to birth, the PFO is necessary to allow blood to bypass the lungs, and deliver oxygen received from the placenta to the rest of the baby's body. After delivery, the baby's lungs expand with air and the pressures in the heart change. The PFO is no longer needed, and it usually closes completely within a couple of months. However, approximately 20% of people never have complete closure of the foramen ovale. Studies have associated this PFO with strokes, migraines, and decompression illness in divers. Large PFO's may cause low oxygen levels in the blood.

How is a PFO identified?

We can detect a PFO by performing a contrast echo study. During this test, we inject tiny bubbles of air into your vein through an IV line, and observe the flow of bubbles by echocardiogram. We can determine if these bubbles cross from the right side of the heart to the left, or if they are all captured and filtered in the lungs. Sometimes, the picture quality is inadequate, and better pictures can be obtained with a transesophogeal echo (TEE). A TEE is also done to better quantitate the size of the opening, or evaluate for other possible causes of stroke. Another test, called a transcranial doppler, can also detect a PFO, and is very similar to a contrast echo study.

Do PFO's cause stokes?

Ten-fifteen percent of all people have a PFO, and most of these people will never have a stroke. There is still some debate on the true risk of a having a PFO, however these people appear to be at increased risk of developing stoke in the future. The risk will also depend on the size of the PFO and individual likelihood to clot. There are approximately 700,000 stokes per year in the United State, and approximately 1 in 3 are cryptogenic. Cryptogenic is a term to describe a stroke without an apparent cause. Common cause of stroke include: atrial fibrillation, carotid stenosis, ruptured aneurysm, or visible blood clot in the heart or aorta. Patients who have had a cryptogenic stoke are more likely to have a PFO, present in 40-70% of such patients, suggesting that PFO's cause strokes. Patients with a cryptogenic stroke have about a 4% chance of having another stroke each year. The probability of a recurrent stoke appears to be less if the PFO is closed successfully, although definitive randomized trials have not yet been completed.

How does a PFO cause a Stoke?

There are two proposed mechanisms for strokes from a PFO. The first proposed mechanism is that small blood clots form in the legs or abdominal veins, and break loose. These small clots normally go to the lungs and are filtered. If there is a PFO, the clot may pass through over to the left side of the heart and go to the brain. This blood clot may lodge in an artery as it becomes smaller, and block important blood flow. If the clot is small and dissolves quickly, then the stroke symptoms last less than 24 hours, and is called a TIA, or transient ischemic attack. If the clot is large enough or persists long enough, a stroke occurs.

The second possible mechanism of stroke is that a small blood clot forms within the PFO itself. The membrane over the PFO may create a pocket and blood clots may form in this space. The clot then may dislodge and go the the brain as described above. This potential pocket may exist even in the absence of a true PFO.

While both of these mechanisms have been seen in individual patients, it is difficult to identify how often this occurs in the general population.

Should a PFO be closed?

A PFO should be closed if the risk of a future stroke is considered high. There remains some controversy on this topic, and the decision to close a PFO will depend on individual circumstances. If a PFO is found incidentally in a patient without symptoms, then the PFO should generally not be closed, as the risk of the procedure may be higher than the risk of any potential stroke. Taking an aspirin once a day is reasonable, but not of any definite benefit.

If the TIA or stroke has occurred in a patient with a PFO, and there are no other explanations for such symptoms in an otherwise young, healthy patient, closure of the PFO could be considered. Treatment with asprin, clopidogrel (Plavix), or warfarin (Coumadin) is often recommended first. If a TIA or stroke has occurred despite the above medical therapy, then closure of the PFO is often recommended.

If two strokes have occurrred despite the use of warfarin, then PFO closure is recommended. Other situations in which PFO closure is considered is in patients with severe migraines or for treatment of decompression illness in divers or treatment of low oxygen levels in the blood.

What are treatment options for a PFO?

If a PFO closure is the selected treatment, it may be done surgically or through the groin vein (percutaneous). A surgical closure requires a central chest incision and splitting the sternum (chest bone). The percutaneous procedure is the most common treatment for this condition, and is done with a small incision in the groin. Both procedures are successful in closing the PFO over 90% of the time.

How is a PFO closed?

A percutaneous closure is done in the cardiac catheterization laboratory, and patients are usually observed overnight. Mild sedation is usually given during the procedure. A local anaesthetic is given, and a small incision is made. A catheter and wire are placed in the leg vein and directed back to the heart. The wire is placed across the PFO in the heart. A large wire mesh device is placed over the wire and observed by Xray. Once in position, the wire mesh is opened and pulled back against the septum of the heart. Then the other side of the mesh is opened, and a sandwich is formed with the mesh over the PFO. The device is released and will stay in place. The guide wire is removed, and the patient is kept at bed rest for several hours so bleeding does not occur. The body will eventually grow cells over the mesh and seal the PFO closed.

What are the risks of PFO closure?

The reported risk of serious complications is 0.2%, including death, stroke, bleeding, infection, or device dislodgement. A partial closure occurs in 1-5% of patients, and no improvement in the size of PFO occurs in 1% of patients. Some patients have reported the development of migraines after PFO closure, which may be more likely in patients with a nickel allergy, or who have larger closure devices. This post-procedure migraine appears to improve or resolve with the use of Plavix, and the migraine headaches resolved after 6 months.

What can I expect during and after a PFO closure?

Patients who are scheduled for a PFO closure will report to the hospital a couple of hours before the procedure for routine lab work and check in. Currently, Dr. Ganellen is performing all PFO closures for the Heart Center. Patients are taken to the cardiac catheterization laboratory and given sedation with Versed for relaxation, but are generally awake for the procedure. A local anaesthetic is given in the groin, and a sheath is placed into the vein. A wire is passed accross the PFO and the closure device passed over the wire. Under fluoroscopy guidance and with the assistance of echo, the device is placed accross the PFO and clamped together. The procedure may take about an hour. Afterwards, patients are kept at bed rest for several hours to avoid bleeding at the groin site. Also, patients will need to take aspirin and Plavix for 3-6 months. Patients are usually discharged the following morning.

Should Atrial Septal Defects (ASD) be closed?

ASD's occur in the same location as PFO's, but are larger holes. Patients with ASD's can have poorly oxygenated blood pass over to the left side of the heart and cause symptoms of fatigue and lower exercise tolerance. ASD's can also cause heart enlargement and rhythm problems. Although some patients with an ASD report no symptoms, they often feel better retrospectively after the ASD is closed. In the past, small ASD's were often left alone, but now it is generally recommended to close all ASD's, large and small.

Can Atrial Septal Defects (ASD) be closed like a PFO?

Yes, ASD's can often be closed just like a PFO, but will depend on the location and size of the ASD.

Is PFO Closure Effective for Migraine Headaches?

Retrospective studies have suggested that patients with Migraine headaches have less symptoms after a PFO closure. This may occur by preventing small blood clots from triggering a migraine, or more likely, by preventing certain substances in the blood from reaching the brain in high quantities. These substances may be filtered out in the lungs instead of passing through a PFO.

In March 2006, the "MIST" trial was reported. This is the first large randomized trial of PFO closure for migraine treatement. 147 patients were randomized: half to PFO closure and half to usual care. There was no difference between the groups in resolution of migraine headaches (3 in each group). However, those with PFO close were significantly more likely to have at least a 50% reduction in headache days (42 vs 23 patients).

In other studies, some patients have reported new migraines after a PFO closure, and clopidogrel (Plavix) appears effective in reducing these headaches (see above). More clinical trials are underway. If you have migraines and a PFO, we can refer you to enroll in a clinical trial for PFO closure.

Links:

British Cardiovascular Interventional Society