Sunday, October 7, 2012

Heterotaxy RAI vs LAI



(While reading this entry, please remember I am not a medical professional.  Also keep in mind that heterotaxy is as different as every patient.  Some individuals may have all the conditions described, or very few.  This is just a guide for basic understanding.)

I felt like I should bring in a special guest illustrator for this post.  Maybe I was a bit ambitious, but I enjoy giving others a chance, especially when the artist has life-long experience with heterotaxy.  At first he was eager, quickly sketching how the internal organs might look, he was very intense.


Then, he went all “diva” on me, demanded breastmilk, a cookie and a nap, whining something that sounded a lot like “I can’t possibly work under these deplorable conditions”.  Of course, I was forced to tuck 16 month old Alexander into his bed and go on without him, even though I think there may be some degree of accuracy to his unfinished drawing.

Humor aside, there are days when his scribbles make me think of heterotaxy.  The literal translation of heterotaxy is “different arrangement”.  There is not a consensus on exactly how that applies, but many feel that the heart is always involved (though, perhaps not to a great degree), and there is some abdominal ambiguity.

Looking at a person from the outside, it’s hard to imagine the complexity that lies on the inside.  Generally speaking, the outside appearance of a person is symmetrical between the left and right side.  A person’s arms are about the same size and length, their feet are about the same size, and the ears are near the same spot.  The left side is much like a mirror image of the right, or vise versa.

On the inside it’s the opposite.  The left side is completely different from the right.  The stomach is on the left side of the body, the liver on the right.  Even paired organs that have one organ on each side of the body are structurally different from each other.  For instance the left lung only has two lobes, while the right has three and the right adrenal gland is triangular shaped and the left horseshoe shaped.
























Heterotaxy disrupts this asymmetrical balance.  During the early days of a pregnancy (between the 3rd and 6th week) the internal organs are forming.  They are created from tubes of tissue that are told how to twist and turn to form the intricate chambers of the heart, blood vessels and digestive tract.  In heterotaxy, these twists and turns don’t happen the way they should, and it’s not entirely understood why.  There are some genetic markers that indicate inherited heterotaxy, and sometimes the syndrome does run in families.  There is also some evidence that heterotaxy (whole or in part) could be related to Primary Ciliary Dyskensia (PCD) which affects the ability of tiny hairs (cilia) in our bodies to move things around they way they should.

 

Most cases of heterotaxy can be organized into two types.  There is Left Atrial Isomerism (LAI) and Right Atrial Isomerism (RAI).  To better understand what is happening, it helps to know the definition of isomerism.  Isomerism is a chemistry term that describes different compounds that are made up of the same parts (atoms), but they are bonded together differently, and that makes the compound completely different.  The use of isomerism when referring to heterotaxy describes optical isomerism, or when those compounds are arranged in such a way they are the mirror images of the other.

Remembering from earlier, think of the outside of our body as optically isomeric; it is made up of the same parts, but in a mirror image to the other.  However, the inside isn’t supposed to be, as there are drastic differences between the right and left internal organs. Therefore, in RAI, all the parts of the right side are present, but mirror imaged to the left, and in LAI all of the left-sided structures are there, but mirror imaged to the right.  This isn’t perfect, but it does help when knowing what to expect from a RAI patient versus a LAI.

In RAI, the structures of the heart are usually greatly affected.  Much of the heart lies on the left side of our bodies, so it makes sense that when the right side of the body is copied, the heart would suffer.  The lungs often end up as two tri-lobed lungs (as the right lung is tri-lobed), the stomach is on the right side of the body versus the left, the spleen is generally absent (asplenia).  The liver usually becomes transverse (midline) and the gall bladder can be affected, and the intestines are often malrotated and the kidneys and adrenal glands can suffer some anomalies.

In LAI one can almost infer the opposite to be true.  The heart tends to have less structural problems, but more prone to electrical ones as the heart’s natural pacemaker is located in the right atrium.  Often, the lungs are both bi-lobed (and bi-lobed lungs are slightly smaller than tri-lobed).  The liver can be midline and malrotated intestines might be present.  Many patients have polysplenia (or many spleens), and while one may think many is much better than none, often times they are not working.  This is known as functional asplenia.  Differences can also affect the kidneys and adrenals.

Because of how complex and extensive this syndrome is, every person affected is different.  One could talk to twenty patients and their families and hear twenty different stories and diagnoses.  These families have teams of doctors to help keep their children in the best possible health.  Our family has been fortunate that Alexander has been so well, but we’re also aware that the luck may not hold out forever.  Our hope is to continue to bring attention to this rare congenital syndrome.  Only through awareness can we convince people to care, and when enough people care change can happen.



I am not a nurse or doctor, nor have I received any formal medical training.  Any and all medical related information on Drawing Heart is the product of a mother’s desperation to understand and advocate for her child.  This blog is the culmination of countless hours of independent research and medical consultation and is meant only to communicate my understanding of Alexander’s condition.  It is not intended as medical advice.  As always, seek the advice of a qualified medical professional to explain your specific diagnosis.

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