Patent Foramen Ovale (PFO)

Patent Foramen Ovale (PFO)

What is a patent foramen ovale (PFO) and what is an atrial septal defect (ASD)?

They are two different types of holes in the heart, connections between the left atrium and the right atrium. They have different causes.

Everyone has a foramen ovale in the womb which allows blood to bypass the lungs while oxygen is coming from the mother via the placenta. When a baby is born and starts breathing, the foramen ovale (which is more of a flap than a hole) snaps shut. In most people it then heals completely. In around 25% of the population it remains open and is known as a patient foramen ovale or PFO.

An atrial septal defect (ASD) is a gap in the tissue that makes up the wall between these two heart chambers, called the septum. ASDs are generally larger than PFOs.

How are they diagnosed?

Both can be undiagnosed for many years, and only be identified later in life. Usually tests are done because of another problem such as palpitations or stroke. A transthoracic echocardiogram may identify an enlarged right heart suggestive of an ASD.

Young patients who have had a stroke may undergo a special kind of transthoracic echocardiogram called a bubble study, where tiny bubbles were injected into a vein during the scan. If they are seen to cross from the right side of the heart to the left side of the heart, that proves that there is a hole that should not be there and that is the most common way that we diagnose a PFO.

What has stroke got to do with PFOs and ASDs?

Strokes in older patients are usually caused by cerebrovascular disease, narrowings in the blood vessels supplying the brain caused by, for example, high blood pressure, high cholesterol and diabetes.

Strokes in younger patients are much rarer and they tend to have a different cause. One cause is something called paradoxical embolism. We all make tiny blood clots in our veins day to day and these are generally carried around the circulation back to the lungs were they are reabsorbed. This is normal. If there is a hole in the heart these blood clots can cross over from the right side of the heart to the left where they can then travel to the brain and cause a stroke. More rarely, they can also travel to the heart and cause a heart attack, or to the gut where they can cause damage. This will only happen if the blood pressure on the right side of the heart is higher than the blood pressure on the left, which generally occurs during certain manoeuvres such as heavy lifting or straining and can be made more likely by being dehydrated.

This is why young patients who have had a stroke would generally have a number of extra tests to rule out these rarer causes, such as blood tests to identify clotting abnormalities and a bubble study to identify holes in the heart.

When do they need to be treated?

ASDs usually do need to be treated and closed. The reason for this is the presence of this hole increases blood flow on the right side of the heart which can lead to becoming enlarged which, over time, can cause heart rhythm disturbances and breathlessness. Some patients have the ASD identified when they have a stroke.

It is a bit more complicated with PFOs. They are very common and in most patients require no treatment whatsoever. In certain situations, we do recommend closure. The most common reason that we recommend closure is stroke. When young people have strokes, it is usually from an unusual mechanism. Any young person who does have a stroke will have a whole range of investigations to look for these more unusual causes, such as blood tests to make sure there are no clotting abnormalities and a bubble study, which is a test to look for a hole in the heart.

What experience does Dr Dawkins have in the management of PFOs and ASDs?

Dr Dawkins runs the structural intervention programme in Oxford and is responsible for closing all of the PFOs and ASDs in the region. He runs the regular PFO meeting where all new referrals are discussed and the brain cardiac imaging is reviewed by a cardiologist and a neurologist.

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    Dr Dawkins has private clinics in Oxford at the Nuffield Manor Hospital and in London at Cleveland Clinic London. Please get in touch if you would like to make an appointment. We can usually arrange to see you within a few days. For urgent appointments, a same-day visit or telephone consultation can often be arranged. To arrange an appointment, please complete this form or call us on 020 7205 2024 (London) or 01865 598040 (Oxford).