102 THE PULSE-CURVE. 



67. PULSE-TRACING OR SPHYGMOGRAM. [The Pulse. With each 

 systole of the heart, a certain quantity of blood is forced into the already filled and 

 partially distended arteries, the resistance in the vessels is lowest between the 

 pulsations, and at this time the arterial tubes are somewhat flattened, but with 

 each systole of the left ventricle the pulse-wave, or rather the liquid pressure within 

 the vessel, is increased, thus forcing the artery back into the circular form. "The 



change of shape, from the flattened 

 condition impressed upon the vessel 

 by the finger or the sphygmograph 

 lever, to the round cylindrical shape 

 which it assumes under the distend- 

 ing force of the blood within it, con- 

 stitutes the pulse," and it indicates 

 Fjg, yi. the degree and duration of the in- 



Sphygmogram of radial artery : pressure 2 oz. Each creased pressure in the arterial sys- 

 part of the curve between the base of one up-stroke tern caused by the ventricular systole 

 arid the ba.se of the next up-stroke corresponds to (Broadbent).] 



a beat of the heart, so that this figure shows five Analysis. A sphygmOffram or 

 heart-beats and part of a sixth. pulse-tracing consists of a series of 



curves (fig. 81) each of which corresponds with one beat of the heart. Each pulse- 

 curve consists of 



1. The line of ascent (a to b in fig. 81). 



2. The apex (P in fig. 83, and b in fig. 81). 



3. The line of descent (b to h). 



(1) The line of ascent, up-stroke, or percussion stroke, is nearly vertical, and 

 occurs during the dilatation of the artery produced by the systole of the left ven- 

 tricle, when the aortic valves are forced open and the ventricular contents are pro- 

 jected into the arterial system. [The ascent is nearly vertical, but in some cases, 

 where the ventricle contracts very suddenly, as occasionally happens in aortic 

 regurgitation, it is quite vertical (fig. 85).] 



(2) The apex or percussion wave in a normal pulse is pointed. 



(3) The line of descent is gradual, and corresponds to the diminution of diameter 

 or contraction of the artery. It is interrupted by two completely distinct elevations 

 or secondary waves. Such elevations are called "catacrotic." The more distinct 

 of the two occurs as a well-marked elevation about the middle of the descent (R in 

 fig. 83 and / in fig. 81) ; it is called the dicrotic wave, or, with reference to its 

 mode of origin, the " recoil ivave." [As the descent corresponds to the time when 

 blood is flowing out of the arteries at the periphery into the capillaries, its direction 

 will depend on the rapidity of the outflow. Thus it will be more rapid in paralysis 

 of the arterioles and very rapid in aortic regurgitation, where, of course, much of 

 the blood flows backward into the left ventricle (fig. 85). In this case, the artery 

 will recoil suddenly from under the finger or pad of the instrument, and this consti- 

 tutes the " pulse of empty arteries."] 



The dicrotic wave, or recoil wave, corresponds to the time following the closure 

 of the aortic valves, and is preceded in the descent by a slight depression, the aortic 

 notch. 



[The tidal wave, or pre-dicrotic, occurs between the apex and the dicrotic wave 

 (fig. 81, d). It occurs on the descent, and during the contraction of the ventricle. 

 The tidal wave is best marked in a hard pulse, i.e., where the blood-pressure is 

 high, so that it is usually well marked in cirrhotic disease of the kidney, ac- 

 companied by hypertrophy of the left ventricle.] 



[In some cases, e.g., mitral regurgitation, the pre-dicrotic wave may be present in some 

 pulse-beats and absent in others (fig. 82), where the tidal wave is present in the largest pulse, 



