Patent foramen ovale, guilty but only as a gang member and for a lesser crime.

n the third century (1,2) of arguing whether a patent foramen vale (PFO), caught repeatedly in the act of begetting paraoxical thromboembolism (PTE) (3–5), poses a significant hreat, some facts seem straightforward; some do not. A FO is required before birth. The fetal right ventricle is not apable of pumping all of the blood through the collapsed ungs. Birth changes this, as the passage through the lungs ecomes mandatory and is facilitated by decreased pulmoary vascular resistance. The Eustachian valve (6) (Fig. 1) or Chiari’s network (7) (ridge or transatrial membrane, espectively, canalizing the blood from the inferior vena cava nto the PFO) are no longer required. On the contrary, they re now counterproductive, impeding fusion of the PFO hat should occur at this stage. If these anatomical structures ersist and remain directed onto a PFO, they constitute ignificant risk factors. The same holds true for an atrial