Foramen Ovale

Develops late in the fourth week of gestation.Fetal cardiac shunt which allows blood to enter the LA from the RA which allows blood to bypass the non functional fetal lungs while the fetus obtains its oxygen from the placenta. Normally closes at birth and forms the fossa ovalis (depression in the RA). It closes due to decreased pulmonary pressures and when the LA pressure exceeds the RA pressure. In about 30% of adults they may still have a small PFO that hasn't closed completely at birth, this can increase the risk of cerebrovascular events. PFOs can cause a left to right shunt which can cause fluid overload of the RA and RV leading to right heart hypertrophy and eventually heart failure. 

Treatment:Cardiac surgery for closure of the PFO.Transcatheter closure in cardiac catherisation lab.

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