A venous air embolus can become a paradoxical arterial air embolus if:
(1) there is a patent foramen ovale
(2) a tiny air embolus is able to traverse the pulmonary circulation
(3) there is a pulmonary arteriovenous (AV) malformation
(4) there is a right-to-left shunt in the heart or lungs
The diagnosis requires exclusion of a separate arterial air embolus, an arterial thromboembolus or arterial atheroemboli.
An air embolus in the arterial circulation can lodge:
(1) in the cerebral circulation, with stroke
(2) in the retinal arteries
(3) in the coronary arteries, with acute myocardial infarction
(4) in the renal or mesenteric arteries
(5) in the extremities
(6) in the skin (with livedo reticularis)
The presence of a large paradoxical air embolus implies a patent foramen ovale or large right-to-left shunt.
