Patent Foramen Ovale, or PFO, is a hole in the atrial septum that separates the atria. This allows oxygen-poor blood to flow from the left atria into the right atria. This increases the volume of blood in the heart. As a result both atria, the right ventricle, and the pulmonary artery are enlarged.

Most PFO defects can be closed by interventional catheterization technique. PFOs may also be closed using a simple suture of patch technique.

Figure 1: Normal heart

Figure 2: Parts of the normal heart.

Figure 3: Heart with patent foramen ovale.

Figure 4: Close-up PFO, showing blood flowing from left atrium into the right atrium.