CH. XXII.] 



SPHYGMOGRAMS 



293 



turgidity arising from venous congestion, will affect the height and 

 form of the sphygmographic record. 



Fig. 259 represents a typical sphygmographic tracing obtained 



from the radial artery. It consists 

 expansion of the artery, and a down- 

 stroke due to its retraction. The 

 descent is more gradual than the 

 upstroke, because the elastic recoil 

 acts more constantly and steadily 

 than the heart-beat. On the descent 

 are several secondary (katacrotic) 

 elevations. 



A is the primary, or percussion 

 wave ; C is the pre-dicrotic, or tidal 

 wave ; D is the dicrotic wave, and E 



of an upstroke due to the 



FIG. 259. Diagram of pulse-tracing. A, up- 

 stroke; B, downstroke ; C, pre-dicrotic 

 wave; D, dicrotic; E,post-dicrotic wave. 



the post-dicrotic wave, and of these 



there may be several. In some rare 



cases there is a secondary wave on the upstroke, which is called an 



anacrotic wave (fig. 260). 



These various secondary waves have received different inter- 

 pretations, but the best way of explaining them is derived from 

 information obtained by taking simultaneous tracings of the pulse, 

 aortic pressure, apex beat, and intraventricular pressure, as in the 

 researches of Hiirthle. By this means it is found that the percussion 

 and tidal waves occur during the systole of the heart, and the other 

 waves during the diastole. The closure of the aortic valves occurs 

 just before the dicrotic wave. The secondary waves on the down- 

 stroke other than the dicrotic are due to the elastic tension of the 



FIG. 260. Anacrotic pulse. 



arteries, and are increased in number when the tension of the arteries 

 is greatest. Some of the post-dicrotic waves are also doubtless 

 instrumental in origin. The dicrotic wave has a different origin. It 

 was at one time thought that this wave was due to a wave of pressure 

 reflected from the periphery, but this view is at once excluded by the 

 fact that wherever we take the pulse-tracing, whether from the aorta, 

 carotid, radial, dorsalis pedis, or elsewhere, this secondary elevation 

 always follows the percussion wave after the same interval, showing 

 that it has its origin in the commencement of the arterial system. 



