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2005-08-10-12 Answer to Case of the week #149 © Jeanty www.TheFetus.net


Answer to Case of the week #149

August 11- August 25, 2005

Pam Ross, RDMS, RDCS, RVT, Doris Baier, RDMS, Philippe Jeanty, MD, PhD,

Tennessee Women"s Care, Nashville, TN

The views of the heart at 19 weeks are shown here:

These are views at 37 weeks, including a 85 MB 4D volume. (Watch out that this is large file and it is probably impractical over modem). If you do not have 4DView or the special 4DFetusView, you can get those from Tools > Computer Pearls > 4DFetusView or simply by clicking: 4DFetusView



We considered the obvious diagnoses of Tetralogy of Fallot and Truncus.. but let us review the 4D volume.

When you load the volume, you should have the default position in which I saved the volume. If you get lost just press INIT (see below) and this will restore the volume to its initial position.

If you look at the top-left panel you should see an image similar to the following:

From this you can see that the baby is seen from the head down, on its back and that the fetus is slightly turned to its left (clockwise rotation on the screen). We will first "turn" the baby so as to make it in a more conventional position.

Note already that the arrow that point to the aorta (the top of the 2 arrows) demonstrates a right-descending aorta. The lower arrows points at the vertebral body.

To turn the baby in the correct position, click on the Rotation Z button above. This will activate the button (make sure you have the A panel selected in the reference image.

This may be trivial to some and there are many ways to do this, but with my old brain it is hard to control the rotation of the image with the mouse, so I prefer to activate the type of rotation (Z in this case) then use the LEFT and RIGHT arrows on the keyboard to turn the plane in small increments.

 

To remember the axis to turn is easy. X and Y are the usual horizontal and vertical axes. So turning around the Y axis is like a dancer pirouetting. The X axis would be like doing cartwheel away from the viewer. And the Z rotation is clockwise (Z is usually used in cartoon to show someone sleeping so think about time spend sleeping).

You should turn the A plane until it look pretty similar to this:

Note that the sternum is now at 12:00 o"clock. Note that in this plane the interatrial septum should be clearly seen and it is incomplete, so this demonstrates a "Atrial septal defect"

Now try to slightly elongate the 4-chambers by turning the baby in the Y axis until it looks like this: (note these are pretty small manipulations, don"t get carried away !)

Now you have a pretty conventional 4-chamber view. Use the "reference slice" to go up and down in the volume. Again, click to select it then use the LEFT and RIGHT arrows on the keyboard to move up and down. As you do so you will see the reference line in the plane B move left to right and so you can check in B how high you are in the fetus.

As you go up, you can clearly see the Ventricular septal defect:

And just a little higher the overriding aorta:

The crucial view is just a tiny little higher: Note the small right ventricle, the right ventricular outflow tract and then an obstruction with no pulmonary artery. Since the right ventricular outflow tract is so small you have to be careful when reviewing the volume to not pass over it. But admire how easy it is to see that the pulmonary artery does not follow. Go back to the videoclip and note how much harder this is to recognize.

Thus the findings are:

  • right-descending aorta
  • atrial septal defect
  • ventricular septal defect
  • overriding aorta
  • pulmonary atresia

and the final diagnosis thus was Pulmonary atresia and ventricular septal defect 

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