Correllation between PFO and Hypoxemia

I have (from TEE) been diagnosed with a PFO with moderate or greater right to left shunting when doing Valsalva.  There is very little shunting at rest.  I also have an ASA and a small ASD (associated with the  PFO) that admits a small amount of left to right shunting (nearly continuously).  I have also had 3 occasions in the last 5 years of Atrial Fibrillation (it's been 18 months since my last event and it is thought that each of the three events may have been triggered by alcohol consumption). Since my last event, I have been switched to Rythmno (225 mg/twice daily) from metoprolol, and it seems to have been extremely effective.
   Since I have had my PO2 checked overnight on impulse, it was found to be low (we live at 8200' elevation).  The PO2 average was 87.5 with some desats.  When checked at 530', my average PO2 was 89, and near sea level, it was 93%.  I was checked for sleep apnea (negative results) and a complete pulmonary workup, also negative.  That's when they found the PFO.
    My question is, what is the likelihood that the PFO could be the primary cause of the Hypoxemia?  Are there any other things that should be checked first?  It is important for me to have a good estimate, as I am considering having the PFO closed with an Amplatzer device implant.  I've had an overnight sleep study, several CT's of my lungs for possible clots, scarring or disease, lung capacity tests and a brief look by an ENT for sinus/airway blockage.  Other than some minor A Fib in the few weeks following a PFO closure procedure, should I be quite concerned about developing chronic A Fib as a result of the implant?  Thanks in advance for any help or advice you may send/

[kenkeith]

An ASA/PFO  can lead to the development of a hemodynamically significant right-to-left shunt.  ASA can be associated with an interatrial right-to-left shunt, causing hypoxemia with right heart non-compliance. There can be severe hypoxemia and pulmonary embolism, complicated by a right-to-left shunt associated with an ASA and PFO.  
Left to right shunting is usual under ASA, if at all, as left side has the greater pressure normally.  The pathophysiologic mechanism for right to left shunt would invlove right ventricular myocardial infarction, pulmonary embolism, and pneumonectomy all elevate right ventricular pressure, leading to a right-to-left shunt through the ASA and the associated interatrial defect. The CT scan would dx those conditions as well as your other tests.

Normal PO2 95-100 at sea level and less than 90 is considered low, and severe would be less than 80. Generalized hypoxia occurs in healthy people when they ascend to high altitudeHigh altitude. Your readings are not very significant if at all.

If you hve right to left shunting, the underlying cause of the increase of pressure within the right atrium should be dx'd.  It can't be very serious as your oxygen level is not significantly low and right to left shunting occurs only during Valsalva!   I don't know  A-Fib's role if any?