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    ok so in tet of fallot, you get a combination of malformations of the heart:

    VSD, pulmonary stenosis, overriding aorta, and right ventricular hypertrophy.

    R -->L shunt, cyanosis. I get that.

    But, what in general determines the severity of the condition? I would probably measure it via the degree of cyanosis, so therefore the pumonary stenosis bit being real important, probably a combo of infundibular stenosis and obstruction of the pulmonary valve?

    However, there was a question on the exam paper which i just sat....and failed :rolleyes:....what is the cause of the tet of fallot? it was worth a couple of marks and didnt know how to answer it, because surely those 4 things have different causes? Or is there one factor which gives rise to the others....in my answer i discuss septation and endocardial cushion formation, but clearly that wasnt right. i cant find the answer to this anywhere, and it wouldnt surprise me if this question came up again...

    ....anyone any ideas?
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    It's all to do with embryology which I can barely remember now, but I think it's before septation occurs (and that's mainly to do with the atria, isn't it? You know how the heart starts off as a tube and basically twists and winds up into a bundle, where all the walls break down and reform to make the normal chambers? As I remember it, TOF occurs due to a defect in this which results in faulty development of the midline structures - the ventricular septum, and the way the aorta and pulmonary artery are divided. Not much help, but I'm sure you'll find it in an embryology book somewhere.
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    ToF is all about the spiral septum.

    Ordinarily it descends in the midline to meet up with the ventricular septum giving rise to the aorta an pulmonary arteries (splitting the truncus arteriosus) and the left and right ventricle.

    In ToF – rather than midline descent you get deviation to the right. This means that you end up with:
    A large aorta (--> overriding as covers left and right ventricles) at the expense of the pulmonary artery which would be small (stenosis).
    The spiral septum will not meet the ventricular septum as it’s now off centre --> VSD.

    The RVH is a result of resistance to flow set up by the overriding aorta, pul stenosis and VSD.

    I think!
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    ToF is the most common cyanotic heart defect, and it's thought to be caused by anterior malalignment of the conal septum, resulting in a clinical combination of VSD, stenosis, and an overriding aorta.
    RVH results from this combination, which causes resistance to blood flow from the right ventricle.
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    (Original post by Fluffy)
    ToF is all about the spiral septum.

    Ordinarily it descends in the midline to meet up with the ventricular septum giving rise to the aorta an pulmonary arteries (splitting the truncus arteriosus) and the left and right ventricle.

    In ToF – rather than midline descent you get deviation to the right. This means that you end up with:
    A large aorta (--> overriding as covers left and right ventricles) at the expense of the pulmonary artery which would be small (stenosis).
    The spiral septum will not meet the ventricular septum as it’s now off centre --> VSD.

    The RVH is a result of resistance to flow set up by the overriding aorta, pul stenosis and VSD.

    I think!
    Sounds about right to me - spiral septum is the word I was looking for, rather than "twisty bits"
 
 
 

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