What The X-ray Shows About The Heart
( Originally Published 1921 )
By the use of the X-rays, if the machine is powerful enough and everything is properly arranged it is possible to look at the heart and see it beating. It requires a good deal of experience to interpret what one sees under these circumstances, and the first step is to know what to look for.
In the first place, the general shape of the heart depends a great deal upon the nature of the trouble. The heart with mitral disease is apt to show a large round shadow. With aortic disease the shadow is shaped like the head of a golf club, that is, with the longest part of the heart lying down, as it were. When there is palpitation, the exaggerated movements are easily seen.
The shadow of the heart lies over the shadow of the spinal column, and of course where the spinal column is behind, the shadow of the heart is Ľobscured. But to the right and left there is a series of curves. The heart looks like a flask standing on top of an inverted bottle. The bottle represents the diaphragm and the flask the heart.
The outline of the flask is divided irregularly into five curves. Starting on the lower left side, we have a curve representing the left ventricle this curve in motion corresponding to the contraction of the ventricles. Just above that is a small curve representing the left auricle. This also is in motion, and if the eye is trained to watch it, it will be seen to move just before the ventricle ; in other words, the auricle contracts to fill the ventricle, and the ventricle then contracts to pump the blood.
Above that is a small curve representing the pulmonary artery. This curve does. not amount to much in the picture, and is often obscured if the aorta is dilated. Above this is a curve representing the aorta as it reaches up from the heart and turns downward. On the left side of the heart there is a continuation of this same aortic curve, somewhat obscured by the great vessels, but often quite visible, and below that is a large curve of the right auricle.
By looking at the heart with the X-ray machine, you cari study the activities of these various chambers of the heart and get valuable information. In many heart conditions the auricle is paralyzed and does not move at all. In old people the aorta is generally enlarged and pulsates. When people have high blood pressure the aorta is always stretched so as to be big and visible. When you know these things, it is interesting t9 see the heart beating. The X-ray also enables us to .make a picture of the heart, but of course that does not give us a definite idea of how it is moving.
One thing that people should know about X-ray pictures of the heart is that they are difficult to interpret unless one knows exactly how they were taken. The X-ray image is a shadow picture, and for that reason changes its shape according to the position of .the light and the position of the object. If you shut your fist, which is about the size of an ordinary heart, and hold it up in front of the light so that it casts a shadow on the wall, you can see that by turning it the shape of the shadow changes with each change in position. It is the same way with the heart, so that the picture of the heart must be taken with this in mind, under standard conditions.
The photographic plate should be in front and against the chest, and the X-ray bulb should be six feet from the plate at a level with the third rib. When these .precautions are taken, the shadow of the heart corresponds closely to the size of the heart, and can be measured and kept as a record.
To realize the importance of getting the light far enough away, hold a candle in front of your fist. Then move the candle back and forth and see the size of the shadow change. But hold your fist near the wall and the candle a good way off, and you will find that the size of the shadow of the fist is the same size as the fist itself.
It is necessary for people to know these particulars, because if a picture of the chest has been taken for some other purpose than the examination of the heart, as, for instance, the detection of a broken rib, the heart picture may be so distorted as to be of no value at all for giving the true size or shape of the organ. By looking at the heart with a fluoroscope (which is the name of the instrument that makes X-rays visible) it is possible to tell which chamber of the heart is in trouble particularly, and that will tell you which valve is involved.
The difficulty of interpreting the heart by the X-ray is that each heart is more or less individual, just as each person is, and the matter of judgment can never be entirely replaced by purely technical knowledge. In other relationships in life we form judgments without always being able to tell why. We say that one man is honest and another is dishonest, because we know it and not because we can always explain it. Similarly, one who is accustomed to observing hearts can tell which are good and which are bad. But it is harder to determine how much variation from a given standard can be allowed in deciding that a heart is not to be called defective.