Paradoxical embolism

A paradoxical embolism, also called a crossed embolism, is a kind of stroke or other form of arterial thrombosis caused by embolism of a thrombus (blood clot) of venous origin through a lateral opening in the heart, such as a patent foramen ovale.

The opening is typically an atrial septal defect, but can also be a ventricular septal defect.

Paradoxical embolisms represent two percent of arterial emboli.

Pathophysiology
Passage of a clot (thrombus) from a vein to an artery. When clots in veins break off (embolize), they travel first to the right side of the heart and, normally, then to the lungs where they lodge, causing pulmonary embolism. On the other hand, when there is a hole at the septum, either upper chambers of the heart (an atrial septal defect) or lower chamber of the heart (ventricular septal defects), a clot can cross from the right to the left side of the heart, then pass into the arteries as a paradoxical embolism. Once in the arterial circulation, a clot can travel to the brain, block a vessel there, and cause a stroke (cerebrovascular accident).