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LEarning centre

Patent Foramen Ovale



A PFO is a flap-like valve or door in the atrial septum. The atrial septum is a thin muscular wall between the 2 upper chambers called the right and left atria of the heart. There is a lot of variation in the size of PFO’s among different people; some are small and tight while others are large and gaping. When it comes to making decisions about treatment, the floppiness of the atria septum and the size of the PFO are important factors.

Investigation Plan

Why do PFO's exist?

During pregnancy, the anatomy & physiology of a fetus is unique to when it is born because the fetus requires special adaptations to sustain itself in the womb. These anatomical adaptations disappear once the baby is born and if they fail to disappear, the newborn may face potential health problems.

An example of an anatomical adaptation in the fetus is the PFO. The PFO is a hole between the atria of the fetal heart that allows blood to pass directly from the right atria into the left atria without passing through the lungs. The fetal lungs are filled with amniotic fluid preventing any passage of blood, and therefore the PFO acts as a lung shunt. Oxygenated blood is supplied by the umbilical cord and travels to the right atrium, directly into the left atrium to be supplied to the rest of the body.


Following birth, the baby's first breaths fill the lungs with air allowing blood to pass through the lungs. At that moment, the left atrial pressure will exceed the right atrial pressure. The higher pressure in the left atrium holds the PFO (door from the right to the left atrium) closed. By adulthood, the PFO should fuse entirely.

In about 25% of adults the PFO does not fuse properly, leaving that passage between the right and left atria. Most of the time the door is closed but there are certain situations where, for a brief moment, the left atrial pressure will drop below the right atrial pressure and the door will open from the right atrium into the left. This represents a period of risk, where blood/clot/debris can travel from the right atrium to the left atrium.

Normal Heart
Normal Heart Patent Foramen Ovale

Symptoms & Health Implications

PFOs are generally asymptomatic -- they do not present any obvious signs or symptoms. As such, most cases of PFO are not diagnosed until patients undergo medical examination due to related or unrelated conditions, such as:

  • Strokes / Transient Ischemic Attack (TIA)

  • migraine headache with aura

Patent - Unobstructed opening of a vessel, duct, or aperture; or failing to close

Foramen - An opening, hole, or passage

Ovale - An opening in the septum between the two atria of the heart that is normally present only in the fetus

Useful Definitions

What does this mean for me?

Having a PFO does not mean that you will necessarily experience negative symptoms or lifestyle impairments. In fact, most patients with a PFO are asymptomatic, and many individuals never even find out that they have one. Most patients who have a PFO live full and normal lives and will never have a complication related to their PFO.

PFO is diagnosed only after a cardiac test called an echocardiogram, or a transcranial doppler. While a regular echocardiogram may detect a PFO, usually a bubble study will be required. This involves administering an intravenous (IV) with a tiny amount of air mixed with intravenous fluid while imaging with ultrasound. This has a very high likelihood of finding a PFO. There are no signs upon physical examination that suggest that a PFO is present. Therefore it often goes undetected without cardiac tests. 

General Advice

  • If you need an IV for any reason, notify your healthcare team that you have a PFO and ask for a bubble trap. We use bubble traps for everyone who has a hole in their heart. It is very common for small amounts of air to enter the system when you have an IV; normally air would be passed to the lungs and would not cause problems. We use bubble traps to prevent air or particles from an IV medication from entering the left atrium and the left side of the heart where they can cause problems.

  • If you are taking long car or plane trips, keep yourself well hydrated and get up and move around every hour or so. Long periods of cramped sitting and dehydration can lead to formation of blood clots in the legs. A blood clot, even a small one, is especially dangerous for people with holes in their hearts. If a clot gets into the left heart and gets pumped to the body it can cause a stroke, heart attack, or it can get lodged in a major artery causing serious problems.

  • Scuba Diving - It is recommended that people who are found to have a PFO avoid scuba diving unless they have been seen and cleared by a doctor specializing in dive medicine. A complication of diving, resulting from resurfacing too quickly, is the “Bends”. The bends refers to nitrogen gas bubbles forming in venous blood. If a hole, like a PFO is present in the heart, those nitrogen bubbles can pass to the left heart can can be passed to the body causing potentially serious complications.

  • Mountaineering - High altitude can cause altitude sickness. Patients who have a PFO may have a greater risk to suffer from altitude sickness.

Next Steps: Investigation Plan

As described in the signs and symptoms section, a PFO is not normally identified until after a stroke, or investigation for a different health concern.

Here are some of the test a neurologist may ask for to investigate a patient with stroke:


Stroke can be a devastating healthcare problem. A stroke can result in a loss of vision, speech, function of an arm or leg, difficulty swallowing and eating, and the ability to perform certain complex tasks. The vast majority of strokes are related to traditional risk factors that cause atherosclerosis (hardening of the arteries). This is especially true in patients over 60 years of age.


Risk factors for stroke include high blood pressure, smoking, high cholesterol, diabetes and a family history of premature vascular disease. Certain heart rhythm disorders such as atrial fibrillation may also cause stroke and are treated with blood thinners life long. Stroke can be caused by blockages in arteries of the brain or by bleeding from damaged arteries in the brain from a variety of causes.

How and when can a PFO be involved in Stroke?

There is a specific group of patients where we consider PFO closure for prevention of recurrent stroke. Neurologists, especially those who specialize in stroke, are especially good at figuring this out. Most strokes in older people are due to traditional risk factors like high blood pressure, diabetes, smoking, high cholesterol, and a family history of premature vascular disease. Patients under the age of 60 who have stroke and are free of traditional risk factors for stroke make up a group of patients we classify as “stroke in the young”.

Stroke in the young (age<55) requires special consideration. Neurologists will extensively investigate these patients for a cause (more on this below). If no clear cause is found we refer to this as a cryptogenic stroke. It is important to note that stroke can be divided into embolic (a clot or cholesterol comes from the heart, aorta, or carotid arteries and travels to an area in the brain and results in a blocked artery), small vessel (involving very thin and fine arteries on the bottom of the brain - usually not related to an embolism, but instead to disease of the little artery caused by traditional risk factors) and hemorrhagic (primary bleeding in the brain - may be caused by trauma, rupture of small aneurysm or other causes)

PFO is a consideration for young people who have had a cryptogenic stroke (a stroke with unknown causes). In 2017, three randomized clinical trials (RCTs) published in the New England Journal of Medicine suggested that among patients with a PFO and cryptogenic stroke, PFO closure and Asprin treatment was better than Aspirin alone in preventing stroke. That is to say, the risk of subsequent recurrent strokes is reduced compared to patients receiving only Aspirin.

Echocardiogram (Transthoracic Cardiac Ultrasound or 'Surface Echo')

A probe will be moved to various locations on the chest or abdomen to produce images of the heart using sound waves. A cold clear or blue jelly is used on the skin to help transmit the sound waves. It can produce images of the structure and beating of the heart. This test does not see the atrial septum that well in many cases. The atrial septum is quite deep in the chest and far away from the probe. By injecting bubbles, it is possible to improve the chances of finding a PFO.

Transesophageal Echocardiogram (TEE)

You will be asked to swallow a probe that will use sound waves to record how well your heart pumps, and whether there are any abnormalities in the valves or chambers. Since the esophagus lies close to the heart, the probe will be able to record a detailed image of the heart and blood flow.

MRI of the Heart: MRI is a technology that uses  powerful magnets to create images of the heart. If a patient is unable to have a TEE we may ask for an MRI of the heart instead.  

Bubble Study (Saline Contrast)

This test is usually added onto a surface echo if a hole in the heart is being considered. A salt solution is shaken with a tiny bit of air to form tiny bubbles, and then injected through an IV into your arm. The bubbles are then followed through an echocardiogram. If there is no PFO, the bubbles will only be found in the right atrium of your heart, and proceed to be filtered out by the lungs. However, if bubbles are seen in the left atrium as well,  this indicates that there may be a PFO or other hole in the heart.

Stroke Symptoms

Stroke symptoms are well documented. For example:


  • Sudden muscle weakness of the face, arm or leg on one side of the body

  • Sudden loss of vision in one eye

  • Inability to walk, loss of balance or coordination

  • Loss of speech, difficulty with communication

Dr. Eric Horlick on Cryptogenic Stroke

How are PFOs related to stroke?

In the normal cardiovascular system, blood clots are constantly forming and breaking down in our veins (venous thrombus - thrombus means blood clot).


A majority of these clots are very small, and they usually travel from the veins in the pelvis and lungs to the pulmonary circulation, towards your lungs. The lungs are capable of filtering these blood clots, and breaking them down. As such, the blood returning to your heart poses no threat to the circulation that supplies the brain, heart and all the organs. 

If you have a PFO on the other hand, there is a risk of a rare event. In most people with PFOs an embolism is a rare event. Patients can live for decades without a problem until one day, a little blood clot, normally taken care of and broken down by the lungs, ends up passing through the heart during a particular time of risk; when the “PFO door” is open. If that happens, a small clot can pass from the right heart to the left and cause problems. If a clot ends up in the brain, it will cause a stroke. The nerve cells (neurons) in the brain are packed very closely together. Any insult to the brain often affects many things at once. Organs like the liver, for example, are large and have the capacity to regenerate making them less sensitive to a tiny clot. The brain, on the other hand is very sensitive.

In summary, PFO’s do not cause strokes, but they provide a portal for them to occur. It is important to note that the odds of this happening are low -- but it certainly can and does happen. Think for a minute that 25% of the population has a PFO, but only few have what we believe is a resulting stroke. For whatever reason in these patients the balance tipped from being absolutely fine to having a stroke.

Treatment Options

Treatment Options for PFO

A vast majority of PFOs do not need to be closed. We make these decisions based on the opinion of an experienced neurologist and cardiologist with expertise in this area. A good team involves good communication between the cardiologist and neurologist to make sure your case is well understood.

Together, your cardiologist and neurologist will recommend which approach is best for your situation.


Patients who are at-risk for strokes are often prescribed a variety of blood thinning medications (anticoagulation or antiplatelet medications) such as aspirin, clopidogrel, warfarin, and rivaroxaban.


An interventional approach to PFO closure is a minimally invasive procedure which involves implanting a device that will seal the PFO. Interventional approaches usually involves the utilization of a catheter-based closure device to treat the PFO.


Open-heart surgery is almost never suggested for PFO closure; in very rare cases, surgery may be required.

PFO closure device

The PFO closure device is made of a wire mesh, and functions to seal the patent foramen ovale, as shown above.

Introducing the Cardiac Catheterization Lab 

Catheter Approach (Interventional)

PFO closure is a minor interventional cardiology procedure which can usually be accomplished in under 20 minutes. Experience of your doctor in performing the procedure is critical, just as it is when it comes to selecting the right patients to undergo the procedure. While in experienced hands the procedure is straightforward, serious complications are more likely to occur if that is not the case.

PFO closure is a minimally invasive procedure, the procedure is performed in a catheterization laboratory, this is a room designed for invasive procedures which contains x-ray equipment, a special procedure table, equipment for ultrasound imaging of the heart, as well as a lot of monitoring and safety  equipment.

Following administration of some intravenous sedation to allow a patient to be comfortable and relaxed, local anesthesia is given in the skin of your leg. We know everyone is a little anxious and our nurses are experts at putting people at ease. Patients will be awake but comfortably relaxed throughout the procedure. If there is discomfort, patients should let the doctor or one of the nurses know and they will help them feel more comfortable. A cardiac catheter (thin hollow tube), is then advanced up to the heart with x-ray guidance. The pressure inside the heart will be measured. The doctor is able to guide the catheter through the heart with the imaging equipment  in the room.

After measuring the pressures in the heart, the catheter will be advanced across the PFO and into one of the pulmonary veins. The pressure will be sampled and a small angiogram will be performed. We will then remove this catheter over a long stiff wire designed for this purpose and will advance a larger thicker tube  to deliver the device used to close the PFO. The device will be prepared and advanced up through the long thick tube and will be deployed. After deployment, the position will be verified with x-rays and an angiogram in the right atrium. When your doctor is happy with the position, the device will be released. Usually we use a suture to close up the hole in the vein in your leg. This is extra insurance to make sure there is no bleeding after the procedure from the vein in the leg.

Our preferred device has been used for many years and  we believe it has an outstanding track record of being safe and effective. It is made of a metal called NITINOL (a nickel and titanium alloy). If the patient is allergic to nickel, we will use an equally good device with almost no metal at all. Before the procedure, we will ask some questions to determine if the patient is allergic to nickel. If possible, we will send them to a special dermatologist for a patch test. 

After your PFO procedure, you will be prescribed an antiplatelet agent, usually aspirin and plavix for six months. Taking these medications every day is important to prevent recurrent stroke as the device matures and becomes completely covered by heart tissue. This process takes about 6 months. Your cardiologist will provide full written guidelines in terms of activities and medications. It is important to follow these guidelines, and adhere to the prescriptions.


A follow-up appointment will be scheduled several months post-procedure to ensure a safe and smooth recovery. An echocardiogram with a bubble study will usually be conducted at this visit  to confirm the PFO hole is closed or on it’s way to being closed. If we still see some bubbles crossing at this visit, don’t worry. It can take up to a year for the bubble study to become negative. Usually within 2-3 months, 80% of people have a negative bubble study, meaning the PFO is no longer present. By approximately 12 months, over 90% of patients will have a negative bubble study.


Your cardiologist will decide at this time whether you should return to your own doctor for follow up or whether further follow up is required.

FAQ: Living with PFO

Living with a PFO: Frequently Asked Questions

Does the size of the defect matter?


Yes. Think of a PFO like a door. The bigger the door, the greater probability for blood clots to pass through and travel to the aorta where it can cause serious damage to vital tissues and organs.


Are there any lifestyle restrictions following PFO closure?

For the most part, you can lead a normal lifestyle. However, in certain situations, care should be taken. For example, we would suggest avoiding scuba diving until we make sure your bubble study is negative. Contact sports should also be avoided for the first six months as you will be on 2 antiplatelet agents.


Can I play sports?


Absolutely. Take about 2 weeks off major activities post procedure to allow you leg to heal. After this period, you can return to your daily routines and interests - including sports. The only restrictions would include contact sports (i.e. football, rugby, lacrosse etc) for the first 6 months

Will my heart go back to normal following PFO closure?

Your heart will continue to function as it was prior to PFO closure. The only difference will be your decreased risk of experiencing an episode of stroke.

What can I expect post procedure?

You will have been fairly well screened for arrhythmia prior to PFO closure. Some patients will develop palpitations which  is likely a result of the device causing extra beats after implantation. It usually lasts for several months at most and then resolves. Rarely palpitations may occur that do not resolve and require a doctor’s visit or ER visit. If this happens please contact your implanting doctor’s office as well as seeking urgent care in the emergency room as required. This is usually a self limited phenomena that can be controlled with medication until it resolves.


Some patients will develop migraine with aura after device placement. This is rather uncommon when taking ASA and Clopidogrel (Plavix)  together after device implantation. Call your doctor’s office for advice if this happens. If you are concerned and require immediate attention, please go to your local emergency room.

Some patients will have minor bruising under the skin because of the antiplatelet medication given post procedure. This will resolve after the Clopidogrel is stopped after 6 months post procedure. If you experience very heavy menstrual periods after PFO closure, please call your doctor’s office for advice.

Will OHIP (public insurance) cover my PFO closure?

Yes. OHIP completely covers PFO closure


How urgent is the treatment?

Once we have made a decision to proceed with PFO closure together, we suggest proceeding with as little delay as possible. While waiting a few weeks is unlikely to be a problem, waiting longer is usually not justified.

Why was my PFO only diagnosed as an adult, despite such advances in healthcare?

A PFO cannot be detected by history or physical examination, it can only be found through an imaging investigation. Either ultrasound, gated CT or MRI of the heart can detect a PFO.

Preparing for your Appointment

Appointment Preparation



Thorough preparation before a diagnostic test or interventional procedure is essential. 

Learn how to prepare for your specific appointment by clicking one of the options below:




Questions specific to your appointment? Call Sue!

Socorro (Sue) Jimeno

Clinical Coordinator, Structural Heart Disease Program 

Phone: 416 340 4800, extension 6258

Fax: 416 340 4741

Questions? Call our Office!


Structural Heart Disease Program (Patients)

Socorro (Sue) Jimeno, Clinical Coordinator

Phone: 416-340-4800, extension 6258

Fax: 416-340-4741

Referrals & Administrative Issues:

Toronto General Hospital 

200 Elizabeth Street | 6E - 249

Toronto, Ontario M5G 2C4

Phone: 416-340-3835

Fax: 416-340-3000

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