Contrast echocardiography<unk> : After obtaining optimal visualization of atrial septum on TTE or TEE, a bolus of agitated saline is injected to an antecubital vein. Subsequently, microbubbles appear in the right atrium. The<unk>  is positive for PFO if microbubbles appear in left atrium within 3 cardiac cycles of their appearance in the right atrium. Valsalva increases right atrial pressure and facilitates
2D TEE with contrast provides superior visualization and is therefore preferred for detecting PFO. When clinically indicated, 2D TEE with contrast is strongly recommended if transthoracic echo is negative.
Bubble study
Age adjusted D-dimer
D-dimer
Pulmonary artery catheter
Aortic ultrasound
Thromboelastography 
Formal echocardiography
Capnography