Foramen Ovale

FORAMEN OVALE

Physiological shunt in the fetus.
It is an opening in the posterior and lower part of the atrial septum of the heart.
At birth, increased pulmonary blood flow when the fetal circulation is transformed into the neonatal circulation pattern, as well as cessation of umbilical venous flow causes the foramen ovale flap to close the opening.
Blood from left hepatic vein and ductus venosus is directed at the foramen ovale thus circumventing the RA.
Foramen ovale moves from RA to LA.
Valve should be in LA.
The size of the FO ranged from 5.8-11.2 mm, with Z values for gestational age ranging from - 0.2 to + 5.5 (mean, 1.9).

1 – Left ventricle

2 – Mitral valve (closed during ventricular

systole)

3 – Flap of foramen ovale

4 - Descending aorta

5 – Septum secundum

6 – Septum primum

7 – Tricuspid valve (closed during ventricular

systole)

8 – Right ventricle

The movement of foramen ovale is complicated as the valve opens and closes twice during each cardiac cycle. It first opens during ventricular systole when blood returning to the heart passes through it on route to the left atrium as the tricuspid valve is closed. At the beginning of diastole the tricuspid valve opens and the foramen ovale closes. The atria contract soon after the tricuspid valve opens forcing blood from the right to left atrium (foramen ovale opens for the second time). At the end of the atrial kick the valve closes for it's second time. The foramen ovale therefore opens for a long period during diastole and a short period during systole.

Normal Foramen Ovale

Flap going from LA to RA secondary to critical aortic stenosis