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Fossa ovalis and patent foramen ovale

Systemic & remnants · detail · Was: foramen ovale PFO ~25%

Oval depression on the right side of the interatrial septum where septum primum has fused with septum secundum: the thin floor is septum primum and the raised rim (limbus) is septum secundum.

Traced from the start

  1. Placenta
  2. Umbilical vein
  3. Ductus venosus
  4. Foramen ovale to left atrium and left ventricle
  5. Fossa ovalis and patent foramen ovale

Detail

Origin
Foramen ovale, functionally shut at birth and anatomically fused during the first year in most children
Patency
Probe-patent foramen ovale in ~25% of adults (autopsy 20-35%), harmless while left atrial pressure exceeds right
Structure
Floor = septum primum; rim (limbus) = septum secundum

When it goes wrong

Deep vein thrombosis with a PFO and a transient rise in right atrial pressure (Valsalva, pulmonary embolism)

Paradoxical embolism: cryptogenic stroke in a young patient; shown by bubble-contrast echo and treated with device closure in selected cases

Ostium secundum atrial septal defect (deficient septum primum at the fossa)

Widely and fixedly split second heart sound with a pulmonary flow murmur; right axis deviation and incomplete RBBB on ECG; late pulmonary hypertension and atrial arrhythmias

Practise this structure

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