Paradoxical embolism

Synonyms and keywords: Paradoxical embolization, paradoxical embolus, cryptogenic stroke, crossed embolism

Overview
A paradoxical embolism is a cause of stroke or other form of arterial thrombosis that is caused by embolism of a thrombus (blood clot) of venous origin through a hole in the heart, typically an atrial septal defect.

Pathophysiology
Paradoxical embolism involves passage of a venous 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 in the wall between the two upper chambers of the heart (an atrial septal defect), 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). The clot can lodge in the cerebral circulation, the coronary circulation, the mesenteric circulation, or in the circulation to a limb.

Echocardiography
A bubble study can be useful in establishing the presence of right-to-left shunting in the evaluation of the patient with suspected paradoxical embolism. It should be noted that bidirectional shunting can also be associated with paradoxical embolism.

Treatment
Treatment of paradoxical embolization involves either:


 * Closure of the defect in the heart( closure of an atrial septal defect (ASD), ventricular septal defect (VSD), or patent foramen ovale (PFO))
 * Anticoagulation
 * Placement of a inferior vena cava (IVC) filter
 * Discontinuation of birth control pills
 * Smoking cessation