Intact Atrial Septum

At the first echo when Shawn was diagnosed Dr. Farrell mentioned a possible complication of what is called an intact atrial septum.  I'm going to try and explain what that is and what that may mean for Shawn. 

The atrial septum is the wall between the two upper chambers (left and right atrium) of the heart.  All fetuses have a hole between these chambers that will close up after birth.  In HLHS'ers this hole is key to their anatomy because without a left ventricle there is no way of getting oxygenated blood to the body.  This hole allows the blood coming from the lungs to enter the left atrium and mix with the blood in the right atrium and then pump to the body.  Dr. Farrell was unable to positively identify that hole in the first echo and was concerned about the pressure and tension this is possibly causing our little guy.  She explained to us the outlook of HLHS along with an intact or highly restrictive atrial septum is not good and greatly reduces his chance of survival. 

The atrial septum is opened up as part of the standard Norwood procedure so fixing this condition is not an issue after birth.  The major complications that arise occur as a developing fetus.  With that wall intact there is no where for the blood from the lungs to go causing a lot of pressure and tension in the left atrium and pulmonary veins from the lungs.  The veins react to this pressure by thickening and muscularizing to toughen up.  That then becomes our biggest threat to our son if it were to happen and there is nothing we can do about it while he is growing in the womb.  He will likely need emergent medical intervention after birth to open the atrial septum and relieve that pressure.  Even after he becomes stable from this procedure and they go in for the Norwood the damage from 4-5 months of high pressures in utero cannot be undone.  The thickened pulmonary veins will still restrict flow from the lungs and he will not be able to deliver sufficient oxygen to his body. 

This condition affects only 6% of HLHS babies so if this is Shawn's case then the odds are truly not in our favor!  Further echocardiograms will hopefully provide the doctors with better images and they can pin down the severity of what's going on in there.  We will keep you posted.