Patient Education Blog

PFO = Patent Foramen Ovale

Anatomy

Some people have a “hole in the heart”, called a “patent foramen ovale” (PFO). This is a connection between the right and the left chamber (atrium) of the heart. We are all born with it – the unborn needs this connection for proper blood circulation. In most people the hole closes in the first few weeks after birth. However, in up to 25 % of people it stays open, equally often in men and women. A PFO usually does not cause symptoms. However, when a person has an acute DVT (deep vein thrombosis) and a clot breaks off and travels with the blood stream, it may cause problems.

DVT and PE in the person without PFO

In the person who does not have a PFO, a clot that breaks off from a DVT travels with the blood stream through the main vein in the abdomen to the chambers of the right side of the heart (color blue in figure 1 and 2). From there, it travels into the lung vessels, where it gets lodged, causing a pulmonary embolism (figure 1).

Figure 1. DVT and PE, no PFO present (graphic design: Jeff Harrison, Wilmington, NC; ©Stephan Moll)

A clot in people without PFO cannot travel to the brain or the extremities, as it always gets lodged in the lung first. The lung is like a sieve: it lets blood through, but not blood clots.

 

DVT and PE in the person with PFO

In the person with a PFO a clot that breaks off from a DVT may cross from the chambers of the right side of the heart through the PFO to the left side (color red in figures 1 and 2) of the heart (figure 2).

Figure 2. DVT in a patient with PFO - leading to a paradoxical embolism, an arterial stroke (graphic design: Jeff Harrison; ©Stephan Moll)

From there it can be carried through arteries (red color in figures 1 and 2) to (a) the brain, causing a stroke (also referred to as “paradoxical stroke”); (b) the arteries of legs or arms, fingers or toes, causing a peripheral arterial thromboembolism, also referred to as “ischemic digit (symptoms: pain, numbness, coldness, white discoloration); and (c) other arteries in the body (such as the abdomen, the coronary arteries around the heart). Such paradoxical embolism is not common in patient with DVT and PFO. However, accurate data as to how often this occurs in patients who have a DVT do not exist.

If such a paradoxical clot happens, a patient needs to be treated with blood thinners for some period of time, and closure of the PFO should be considered in certain patients. However, the decision whether the PFO should be closed or not is difficult, as (a) PFOs are found in a large proportion of the normal population who does not develop strokes, so that the question always arises whether the PFO found in a patient with stroke or peripheral arterial clot is coincidental or truly contributed to the clotting event; (b) a patient may remain on long-term blood thinners for the DVT, in which case PFO closure is not needed, as the warfarin protects the patient from recurrent paradoxical clots; (c) PFO closure is not without complications, (d) most patients with stroke, DVT and PFO will remain stroke-free in the future without a PFO closure, and (e) studies are ongoing trying to define which patients may benefit from PFO closure. Consultation with a variety of specialists who work together is often needed for solid decision-making – a hematologist (to address the DVT issues), cardiologist (experienced in PFO closures) and a neurologist (in case of stroke) or vascular surgeon (in case of extremity clot).

Once the PFO has been closed, the patient should receive an appropriate length of warfarin therapy for the DVT that he/she has. That length depends on what risk factors triggered the DVT in the first place, and may only be 3 months long. However, if strong risk factors for a recurrent DVT are present or the patient is assessed to be at high risk for another clot in the future, long-term warfarin may be given. The topic of “Length of Warfarin Therapy for DVT and PE” will be addressed in a separate future Clot Connect blog entry.

Diagnosis

Search for a PFO is typically done when working a patient up for the cause of an unexplained stroke, arterial extremity or abdominal clot. A PFO is diagnosed by an echo study of the heart (= cardiac echo = echocardiogram); the hole can often be seen on the echo. However, sometimes it cannot be seen and then a “bubble study” is needed, during which agitated (bubbly) normal saline is injected into an arm vein; if a PFO is present the bubbly normal saline can be seen on the echo passing from the right side of the heart to the left. An echo performed with a tube that a patient swallows (= transesophageal echo or TEE) is more sensitive in picking up small PFOs than an echo done through the chest wall (= trans-thoracic echo or TTE). Thus, if one wants to fully rule out a PFO, one can get a TTE first; however, if it does not show a PFO,  a TEE with bubble study should be obtained.

Patient Questions/Comments/Examples –  Explanations

Question #1: “I have had a deep vein thrombosis in my leg. I am always afraid that a piece will break off and travel to my brain and cause me to have a stroke. How often does that happen?”

Answer #1: A DVT typically does not lead to a stroke. However, rarely this does happen in the patient who has a “hole in the heart” (= patent foramen ovale = PFO), as discussed above.

Question #2: “My 30 year old son had a stroke and has a PFO. It was not found on the regular echo, but was found when they did a transesophageal echocardiogram. The docs felt that the PFO and factor V Leiden both were probably what caused his stroke. They could find no other reason.”

Answer #2: “In unexplained stoke search for a PFO is indicated. Other work up for unexplained arterial clots has been discussed here: Clot Connect blog on unexplained arterial clots. The best, most sensitive test to detect a PFO is a transesophageal echocardiogram (=TEE) with bubble study. If a PFO is found, a Doppler ultrasound of the legs should be done to look for deep vein thrombosis. A CT venogram or MR venogram of the pelvis would also be appropriate, if the Doppler ultrasound of the legs does not show evidence of DVT. While factor V Leiden does not typically lead to arterial clots, such as stroke, it can contribute to DVT formation and then, if a PFO is present, to a paradoxical stroke, as described above”.

Reference

Kent DM et al. Is patent foramen ovale a modifiable risk factor for stroke recurrence? Stroke 2010;41:S26-S30.

Disclosure: I have no financial disclosure relevant to the content of this blog entry.

Last updated: Feb 14th, 2011

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