• Non-Fusion of the septum secumdum and septum primum following birth.
• Common among the general population approximately 25%.
• Associated with cryptogenic strokes especially if large PFO, septal aneurysm,  evidence of right to left shunt, and a prominent eustachian valve.
• Closure can be considered in selected patients with cryptogenic stroke.

Role of ECHO

• Echo plays a crucial role in diagnosis.
• Visualiation of a very mobile or aneurysmal intra-atrial septum may be the first clue.
• Colour doppler may show evidence of shunt.
• Bubble test a key test to confirm a PFO by early (less than 3 beats) bubbles crossing into the left atrium.

• Subcostal view show evidence of very mobile intra-atrial septum.
• Not the red colour doppler that seems to cross the intraatrial septum suggesting presence of a PFO.

• Bubble study confirming presence of right to left shunt.
• Note the bubbles cross early withing 3 cardiac cycles. Late bubbles would be suggestive of possible pulmonary shunt.
• The test can also be completed during a valsalva. Occasionally this may be the only time a shunt occurs.