Patent foramen ovale is probably the commonest congenital heart defect. (Bicuspid aortic valve will run close to it ! )
Note : PFOs cannot be called as a true disease , since it is a benign anatomical defect with little or no hemodynamic impact.
Consider this scenario . . .
The incidence of PFO could be as high as 20% of adult population. It means nearly 100 crore people of this planet will suffer from this entity !
When does it become significant ?
Paradoxical embolism : In young persons with cerbro vascular accident , PFO s are more commonly observed , implicating some form form of venous to arterial embolus .
In some persons it is believed , it can shunt few CC of blood from right atrium to left atrium at times of right atrial hemodynamic stress. Like severe physical straining (valsalva like )
In seriously ill ventilated patients PFOs can worsen the hypoxia especially with PAPP mode .
When does it become a life saving savior ?
- In patients with DTGV and intact IAS even a a small PFO can sustain a life till , emergency surgery or intervention is done .
- In patients with severe pulmonary hypertension the PFO may act like a safety valve, opening at a critical moment and decompress the right atrium and which indirectly relieves the RV wall stress as well .
Now , it is considered PFO is related to migraine by some means ! ( What means !) The belief has strong evidence base that has lead the aggressive interventional cardiologists to find a new hole to close . This indication , if approved will have a perennial supply of patients as there are 100 crores of them .
How will you differentiate a PFO from a small ASD ?
Size alone can be a useful pointer in differentiating a ASD from PFO.
A PFO can measure between 2 to 10mm ( most measuring between 4-6mm diameter)
Size matters ! The upper limit of PFO is the lower limit of ASD .
Practical experience suggest any defect above 7mm should alert us about the possibility of true ASD.
Other useful clues
- PFO are always restrictive (Use pulse doppler probe right across the PFO /ASD in subcostal view .If you pick up a gradient > 4mmhg (velocity 1 m /sec) PFO is confirmed.
- Most ASDs do not show any significant gradient
- Right ventricle and right atrium should be normal in PFO (Unless due to some other cause )
- Doppler flow across pulmonary valve can be very useful . If it exceeds 1.5m/sec , left to right shunting is likely to be significant and PFO is unlikely.
Is there an entity called restrictive ostium secundum ASD ?
If so , how will you differentiate it from PFO ?
Yes , we have ,especially in cyanotic heart disease
Like TGA , Ebstien etc .
Isolated restrictive secundum ASD is extremely rare .
* There is no way to differentiate a restrictive ASD from a similar sized PFO .
What is the role of TEE in diagnosing PFO
It has a major role in delineating the IAS anatomy .