I read that foramen ovale opens in 30% of adults. I do not know how much of these openings can then close again. Probably, none. It is not pathogenic if no symptoms.

It allows blood to enter from right atrium to left atrium (fetal), but from left atrium to right atrium in adults. Assume that 50% of blood is doing so in adults. This means that 50% of blood is not oxygenated. Heart has to pump stronger to get some level of oxygenated blood as before.

Some thoughts about manifestations of open foramen ovale

  • hypertension
  • ischemic hypoxia
  • Clubbing
  • possible organ failures
  • higher risk for infections, SIRS and sepsis

Therefore, I think open foramen ovale can be a risk factor for myocardial infarction.

What are the manifestations of an open foramen ovale in adults?

  • 1
    $\begingroup$ As I recall the 30% of patients are only probe patent and therefore of little significance in terms of blood mixing under normal conditions where right sided pressure is lower than left sided (therefore RA will NOT flow into LA). They are at higher risk of stroke from paradoxical embolism (which does cross through the PFO). I'm not convinced by any of those bullet points as your original premise is off - a PFO will not cause a 50% shunt right to left. $\endgroup$
    – Rory M
    Apr 8, 2014 at 10:44
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    $\begingroup$ I think what you may be thinking of is Eisenmenger's Syndrome though you should also read through the Cyanotic Heart Defects section. Can you also clarify what you mean by "COPD-hypoxic-nails"? $\endgroup$
    – Rory M
    Apr 8, 2014 at 10:46
  • $\begingroup$ @RoryM COPD-hypoxic-nail like curved nails caused due to hypoxia in peripheral system. $\endgroup$ Apr 8, 2014 at 14:29
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    $\begingroup$ Clubbing? $\endgroup$
    – Rory M
    Apr 8, 2014 at 15:08

1 Answer 1


A fully patent foramen ovale (pfo) is rare however a partial or small pfo is present in about 30% of the population.

Now the manifestations you described are partially correct. A pfo causes a left to right shunt in the adult whilst a right to left shunt in the fetus. In the fetus this is normal. In the adult, it is left to right because the left atrium is at higher pressure than the right. Due to this some of your manifestations are the wrong way round but still correct.

For example you mentioned hypertension, but presumably you meant systemic hypertension. It is more common at least in the early stages to get pulmonary hypertension. The pressures in the left atrium cause the pressures in the right atrium to increase when there is shunting. This is frequently seen when pressures in the left are increased due to factors like systemic hypertension. Coronary artery disease can also worsen the shunt and increase pressures in the right atrium and pulmonary pressures because the left ventricle can be stiffer.

Despite all this the more common presentation of a clinically significant pfo is right heart failure. Volume overloaded,the right heart dilates and fails. This will cause the usual presentation of right heart failure i.e. peripheral oedema, ascites and hepatomegaly.

Of course increased pulmonary pressures also causes strain to the right heart and can also cause right heart failure.

They then may go on to develop congestive cardiac failure and the exertional dyspnoea that comes with it. The inadequacy of the right heart can lead to excess strain to the left heart through a number of mechanisms that leads to it also failing. Dilation of the right heart can also lead to atrial fibrillation which in turn leads to stroke all being other possible presentations.

Cyanosis usually doesn't occur at least early in the disease as there isn't a shift from right to left (unoxygenated to oxygenated) but the other way round.

The severity of the pfo will lead to the severity of the clinical manifestation and how early it is picked up. Most people have routine checks of their heart (the murmur is usually pretty loud) so it is frequently corrected before any clinical disease manifests. In patients with small pfos they may never notice unless they become hypertensive or put strain on their heart during pregnancy. Yes they have a slight disadvantage as they lose some oxygenated blood but not anything noticeable.

If anything is unclear or you have more questions, please ask.

  • $\begingroup$ Thank you very much for your clear answer! I corrected the mistake in my question body. I am digesting your answer and will ask when I get new thoughts which I cannot solve myself. $\endgroup$ Apr 12, 2014 at 7:20

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