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A finding that is indicative of a patent foramen ovale (PFO) is the detection of a right-to-left shunt during a bubble study. In a bubble study, microbubbles are introduced into the venous circulation, and their passage into the left atrium would indicate that there is a communication between the right and left atria, characteristic of a PFO. This occurs due to the failure of the foramen ovale—a normal fetal structure that usually closes after birth—to fully seal, allowing blood to flow from the right atrium to the left atrium under certain conditions, such as increased right atrial pressure.

The presence of a right-to-left shunt can lead to important clinical implications, such as the potential for paradoxical embolism, where a thrombus can travel from the venous system to the arterial system, increasing the risk for stroke. Consequently, identifying this shunt during testing is essential for diagnosing a PFO.

Unidirectional flow through the septum would typically suggest a condition that does not involve a significant shunt, as it would imply that blood only travels in one direction, minimizing the risk for complications associated with a PFO. Similarly, left-to-right flow in the atria would indicate the opposite