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In the early days of cardiac catheterization,
The x-ray tube, image intensifier and camera remained stationary,
while the patient lay in a cradle that was rotated from the RAO to
the LAO projections. Cranial and caudal angulation were not possible
at those times. These "straight" RAO and LAO views were limited because
of foreshortening of the left anterior descending and circumflex coronary
arteries and the overlap of vessels.
Today, all cardiac cath labs are equiped with an image
intensifier and camera that can be rotated along the RAO/LAO as well
as a cranial/caudal (towards and away from the patient's head) projections.
Regardless, the straight RAO may be of occasional value, since it
may be the only RAO view that clearly demonstrates the very proximal
portion of the LAD or the origin of the obtuse marginal and left postero-lateral
branches of the circumflex.
In the Right Anterior Oblique or RAO view,
the camera is rotated along a vertical axis towards the patient's
right, as shown at the bottom of the page. Once again, the size of
the heart has been purposely exaggerated for purposes
of illustration. Please note that the ventricular septum lies in a
plane between the right shoulder and the left nipple. Thus, in the
RAO view, the camera "looks" at the outline of the septum. The atrioventricular
plane is seen on edge, since it sits roughly at right angles to the