chalooch101
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how can the asd be protective?
wont the pressure be higher in the RA due to the increase RV pressure?
also a lot less blood is going to the aorta instead of the pulm circulation wont the LA pressure be smaller than the RA, therefore causing a R to L shunt in the ASD?
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| salmonella
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In fetal life, theres a foramen ovale that can be called an ASD if it persists in a neonate.
In a postnatal life, we know that left sided pressure is more than the right side. Hence, if theres an ASD (Patent foramen ovale), there will be a left-right shunt. (D/t increased left sided pressure. This is a non-cyanotic condition which can become cyanotic over a period of years , due to increased right atrial pressure(which is the result of left sided blood flowing into the right atrium,) which will cause pulmonary hypertension. Now right atrial pressure may exceed that of left atrium, this causes a rt-left shunt which is cyanotic.
As for your question:
wont the pressure be higher in the RA due to the increase RV pressure?
Why would increase in RV pressure result in higher RA pressure? There's no regurgitation of blood from RV to RA as tricuspid valve is working fine..
Hope this helps.
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| salmonella
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Ooops sorry about the above explanation. I thought you were asking about PLAIN ASD and not with tetralogy of fallot.
Heres the explanation:
Tetrology of fallot:
1) Pul. stenosis (Less bld going to the pul. trunk
2) over-riding aorta(More blod going to the aorta as blood fro both rt and left ventricles is going to the aorta as it is overriding them both)
3)Hence I/V septal defect
4)Rt ventricular hypertrophy due to increased pressue in the RV
A whole LOT blood is going to the aorta as there is also a right -left shunt (Cyanosis)
AND the fact that a lot lesser is going to the pul. trunk (D/t stenosis)
I dont know if ASD is protective or not(wasnt in Kaplan) A child definitely survives because there is a mixing of blood. If there was absolutely no mixing of deoxy n deoxyg. in defects like transposition of great vessels and persistent truncus arteriosus, the fetus does not make to the postnatal period. (I.e. the infants born alive with these 2 defects do have some septal defects)
An ASD in a child with tetrology, creats a left-rt shunt as pressure of the left is more (D/t a rt-left ventricular shunt, and the fact that the bld from LV goes to only that HALF of aorta that projects from the LV and not the part that over rides the RV)
Though, I still fail to understand how can this be protective. because the blood will run in circles. As stenosed pul trunk creats a back pressure in the RV which gives off that extra bloof to the LV due to the I/V defect. Now if there was an ASD blood from the LA starts pouring into the RA and this blood empties into the RV , so the bld runs in circles.
How is this protective? where did u read it?
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| salmonella
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* no mixing of oxygenated and deoxygenated bld
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* The ASD paragraph is incorrect .
An ASD in a child with tetrology, creats a left-rt shunt as pressure of the left is more (D/t a rt-left ventricular shunt, and the fact that the bld from LV goes to only that HALF of aorta that projects from the LV and not the part that over rides the RV)
Ofcourse, there is a left-right atrial shunt in a tetrology patient with an ASD BUT it is NOT due to the above mentioned explanation. It is due to the NORMAL phenomenon that left atrial pressure is more than that of rt atrium.
So sorry for the inconvenience.
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| chalooch101
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wont the pressure ion ther right atrium be higher than the left because the left will not develop a higher pressure at birth becasue there is a lack of return fromt he lungs due to the R to left shunt
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