Table 1.

Characteristics of simple and complex PFOs

PFO category	Anatomical characteristics
Simple:	● Standard anatomy, i.e. none of the below
Complex:	● Long tunnel length (≥8-10 mm)
	● Multiple openings into left atrium
	● Atrial septal aneurysm
	● Excessive movement of atrial septum
	● Large opening
	● Shunt at rest
	● Hybrid defect
	● Thick septum secundum (≥10 mm)
	● Prominent Eustachian ridge
	● Eustachian valve or Chiari network
	● Angle between PFO and IVC ≤10°

PFO: patent foramen ovale; IVC: inferior vena cava.