Previously thought to be a relatively benign anatomical variant, the PFO has now been linked to a spectrum of symptoms, diseases and disorders such as migraine with aura, premature stroke, myocardial infarction, sleep apnoea, decompression illness, altitude sickness and unexplained dyspnoea to name just a few. There has also been a link to Alzheimer’s disease and Chronic Fatigue Syndrome recently reported.
Clearly the lung is the organ responsible for gas exchange but many don’t realise it is also acting as a huge blood filter capturing thrombus (pulmonary emboli) and neutralising chemical toxins and signallers such as prostaglandins and interlukins, just to name a few.
Reversal of the PFO shunt(R-> L) towards the arterial side occurs during any valsalva manoeuvre such as straining, snoring or coughing resulting in a flood of material bypassing the lung filter.
In some large PFOs the shunt is always reversed. Solid thrombus, microscopic platelet aggregates and metabolites can affect organ function and even cause infarction and ischaemia in organs such as the brain, heart, kidneys and even leg claudication.