TTE is considered the preferred diagnostic test of choice as it is noninvasive. The Diagnosisīoth transthoracic echo (TTE), a cardiac ultrasound performed from the chest wall, and transesophageal echo (TEE), a cardiac ultrasound performed from the esophagus, have been used for the diagnosis and assessment of PFO. The etiology and clinical significance of these findings are unclear but may represent multiple subclinical paradoxical embolic events across the PFO. Additionally, the average number of ischemic brain lesions as seen on MRI in experienced divers with PFO has been reported to be twice as high as in divers without PFO (11). As mentioned above, the risk of DCI in sport divers is quite low but is increased by at least five-fold in the presence of a PFO (1, 2, 3). Subsequently, the importance of PFO for DCI in divers has been further investigated (1,7, 8, 9). In 1986, it was first suggested by Wilmhurst and colleagues that a cardiac right to left shunt may be important for a paradoxical gas embolism in scuba divers (6). This may result in “larger” PFOs in older adults. The cause of this is unknown, but in part may be due to known elevations in right heart pressures with aging causing the pressure difference between the left atrium and right atrium (which keeps the PFO closed) to lessen. PFO diameters are quite variable in size ranging from 1-19 mm/0.04-0.75 in, with the average size being larger in older adults (4), suggesting PFOs may continue to enlarge during life. Anatomic closure of the PFO occurs later in infancy in most people but is incomplete in approximately 25% of the population (4, 5), leaving these individuals at risk for right to left shunting. The resulting atrial pressure differences compress the septum primum against the septum secundum, functionally closing the PFO. At birth, pulmonary blood flow increases greatly, increasing left atrial pressure. Normally, a portion of the blood from the inferior vena cava passes from the right atrium to the left atrium through the PFO during fetal life, bypassing the lungs. Autopsy specimen showing a patent foramen ovaleĪ PFO is an integral part of the normal fetal circulation.

Skin bends