How will you quickly differentiate PFO from small ASD ?
Posted Jul 13 2010 10:41am
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 .