A patent foramen ovale (PFO) is a flaplike opening between the atrial septa primum and secundum at the location of the fossa ovalis that persists after 1 year of age. With increasing evidence being found that PFO is the culprit in paradoxical embolic events, the relative importance of the anomaly is being reevaluated.
Bubble study
Age adjusted D-dimer
D-dimer
Pulmonary artery catheter
Aortic ultrasound
Thromboelastography 
Formal echocardiography
Capnography