A patent foramen ovale or PFO is a congenital heart defect consisting of a small hole between the right and upper left atria of the heart (the two upper chambers). It is normal in a newborn infant, and appears to be merely part of the normal growth of the heart in utero. However, once the newborn starts breathing, pressure in the left atrium starts to exceed that in the right atrium and tissue called the septum primum is forced against the hole. Eventually, the tissues fuse together, usually about three months after birth.

However, in about 30% of adults, the hole remains open, allowing blood to flow directly between the atria. Most individuals with the condition suffer no symptoms, ill effects or complications and live normal lifespans. However, it can cause complications, such as:

  • Enlarged right atrium - the pressure on the left atrium is higher and can actually stretch the right atrium, which operates at lower pressures because it only supplies blood to the lungs. This can be worsened by overall high blood pressure.
  • Extra pressure can also lead to pulmonary hypertension, even when blood pressure in the rest of the body remains normal.
  • The extra pressure can result in the right atrium ceasing to work properly at all.
  • The extra pressure can damage capilliaries in the lungs, leading to scarring and lung damage.

On House, a PFO is often part of the differential. It is often linked to different types of endocarditis.

A PFO can be diagnosed with an echocardiogram, bubble study, EKG or even careful examination with a stethoscope. However, none of these can definitively find a PFO and if the blood flow beween the two is small, it may not show up on tests.

Patent foramen ovale at Mayo Clinic

Community content is available under CC-BY-SA unless otherwise noted.