PHYSIOLOGY OF AORTA AND MAJOR ARTERIES 



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fig. 10. Reconstruction of aortic- 

 pressure pulses, showing comparison 

 between control in aortic arch (dotted 

 lines) and records taken simultaneously 

 with their controls at indicated distances 

 down the aorta from the arch (solid 

 lines). Below, five of the above ten, semi- 

 diagrammatically superimposed on a 

 somewhat larger scale, with a repre- 

 sentative control. [From Hamilton & 

 Dow (42).] 



peripheral pulse were recognized even in the days 

 when pressure recordings were made using low 

 frequency manometers. When Frank (28) developed 

 his high fidelity manometer, he established this 

 difference in precise terms. This was verified and 

 amplified by the work of Wiggers and his associates 

 (1, 135, 136) and Hamilton and his group (40, 42, 

 140) in this country, as well as by continued work in 

 Europe (17, 29, 57, 58, 75, 115, 117, 133). In con- 

 trast to the broad systolic crest of the central pulse, 

 the femoral artery pulse, for example, shows a high, 

 narrow systolic profile. Sudden slope changes, such 

 as the shoulder of the central pulse and the incisural 

 notch, are no longer present in the distal vessel, 

 having been lost through damping (fig. 10). Such 

 damping is most obvious when the aortic pressure is 

 low, and least obvious when the pressure is at hyper- 

 tensive levels. This is probably related to the fact 

 that the visco-elastic properties of the wall are more 

 prominent at low pressure levels. 



The changes in contour are similar to those that 

 would be obtained if a central pressure pulse were 

 recorded by a slow-frequency manometer system, 

 which would allow an overswing of pressure in 

 systole, and an exaggerated fall to a low level in early 



diastole. The German workers, after Frank, have 

 therefore thought of the portion of the arterial bed 

 which stores blood in systole, i.e., the arterial reservoir 

 or Windkessel, as having a lumped distensibility 

 value, like a manometer (12, 17, 58, 132). It should 

 be remembered, of course, that the distensibility of 

 the arterial bed is not that of a single membrane, 

 and it does not follow that the arterial reservoir could 

 vibrate as a single unit as a manometer system does. 

 Despite much descriptive work on the contour 

 changes which attend propagation of the pulse, our 

 basic knowledge of the underlying principles remains 

 incomplete. In their classic paper on this subject, 

 Hamilton & Dow (42) presented for the first time a 

 mapping of the changes in pulse form in the dog as 

 recorded serially from various points in the aorta 

 (fig. 10). This mapping reveals that as the wave 

 moves toward the periphery the steep initial anacrotic 

 rise remains unchanged in slope, but persists for a 

 longer time. Hence the deflection marking its end, 

 or the shoulder, comes at progressively higher pressure 

 levels. The systolic peak becomes gradually narrower, 

 so that the time from the start of the pulse to the 

 peak is reduced. Hence, in spite of the transmission 

 delay of the start of the wave, the peak is reached at 



