Pulse In The Jugular Vein
( Originally Published 1921 )
The veins are fitted with valves opening toward the heart, so that the waves from the heart are stopt. It happens that in the jugular vein the first valve as we come from the heart is located just behind the collar bone, where the sterno-cleido-mastoid muscle is attached. This muscle receives its name from its attachment. It is attached to the sternum or breast bone, the clavicle or collar bone, and the mastoid, or the bone to which the ear is attached. It is a prominent muscle in the neck, and shows plainly when the head is turned from side to side. Right behind this muscle, where it splits into two pieces, one to join the collar bone and the other to join the breast bone, is the place where we study the pulse in the jugular vein.
Of course the blood is flowing through the vein toward the heart, but the waves from the heart as it moves go up stream, as it were, and appear at the root of the neck. The most important wave is that caused by the contraction of the auricle. There is another one caused by the beating of the ventricle, and another caused by the damming back of the blood coming to the heart while the ventricle is beating.
Later on, when I describe the study of the heart beat according to its autograph produced by the electricity from the heart, I will tell, you that the electrocardiogram, or electrical heart beat picture, shows three principal electric currents a small electric current caused by the contraction and work of the auricle; a sharp, quick current caused by the beating of the ventricle; and a third sluggish wave caused by the contraction of the ventricle. Three things are seen also in the jugular pulse a wave caused by the contraction of the auricle, a wave caused by the beating of the ventricle; and one which is caused by the damming back of the blood in the jugular while the ventricle is contracting. The heart is filled with a fluid which is not compressible and has to be forced out of the heart against a considerable amount of resistance in the arteries. So when the ventricle begins its work, the first thing that it does is firmly to take hold of the blood by contracting upon it,but it really does not contract much because it comes up against a solid mass of blood in the heart, which a moment later it squeezes out into the circulation.
This triple activity is so fundamental in understanding the heart beat that it is worth this amount of consideration. By the jugular pulse, as we get it traced on paper with a polygraph, we are enabled to study accurately the relation between these three important events.
In connection with the pulse as we study it in the jugular vein, it is necessary to know that the carotid artery is right near it, and that the tracing corresponding to the contraction of the ventricle comes from this blood vessel as well as from the vein.
For that reason this wave is called the C wave, the one from the auricle being called the A wave, and the third the V wave. In the electrocardiogram the electric currents generated by the activities of the heart that cause the waves in the vein are named P, R, and T. These names are universally adopted now, and are a great convenience in talking about these things.