Patent foramen ovale pathophysiology


 * Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

Overview
A patent foramen ovale or PFO is not considered an atrial septal defect because there is not a permanent hole or defect in interatrial septum. Instead there is a flap-like structure that periodically opens which allows blood to shunt between the two atria. As a result, it is also sometimes called as a probe patent (PFO). This flap-like structure functions like a one-way valve mechanism that only opens to allow blood to flow from the right atrium to the left atrium during times where there is an increase flow or pressure in the right atrium. Elevation of pressure in the pulmonary circulatory system (i.e.: pulmonary hypertension due to various causes, or transiently during a cough or valsalva maneuver) can cause the foramen ovale to open. Because of this one-way valve like mechanism and the dynamic nature of the right to left shunting, a patient is often asked to perform a Valsalva maneuver during a echocardiographic bubble study to facilitate transit of bubbles from the right atrium to the left atrium.

Pathophysiology
A patent foramen ovale is a flap-like structure that periodically opens and allows shunting of blood from right-to-left atria. As a result, it is also sometimes called as a  'probe patent'  patent foramen ovale. The shunting could occur with a transient elevation of pressure in the pulmonary circulation that occurs during pulmonary hypertension, valsalva maneuver or cough. The size and the degree of right-to-left shunt appear to be important in determining the pathological significance of patent foramen ovale, ,. In a multi-center randomized trial, larger patent foramen ovale were found to be more associated with cryptogenic stroke than smaller patent foramen ovale.