104 PULSE KECORDS IN THEIR RELATION TO 



pagate a positive wave in the uppermost chamber. 1 Now the 

 movements of the A-V line are also offered as an explanation of 

 an earlier negative wave (second negative or " x' " depression), and 

 the view, as we shall subsequently see, has much to support it. 

 If the descent of the A-V line is sufficient to produce a negative 

 wave, its ascent must assuredly be adequate to determine a second 

 wave of equal intensity but of opposite sign. The explanation is 

 a feasible one, and there remains but one serious difficulty. A 

 positive wave of the sort, if propagated, may be entirely swamped 

 by other events occurring at or about the same time. And the 

 event which has to be considered is the effect of the lowering of 

 ventricular upon auricular pressure. It must be noted that the 

 factor can only be of avail between the S.C. and A.O. points ; and 

 until there is more unanimity as to the timing of these events 

 opinion must necessarily vary as to the part played by the A-V line 

 in the production of the " v " wave. 2 



The interpretation of the " v " wave which has just been dis- 

 cussed attributes it to a movement of the ventricle, and makes it 

 independent of auricular contraction or relaxation. Fredericq has 

 found that when the ventricle is thrown into a state of fibrillation, 

 the wave is abolished. Franois-Franck and Morrow, on the other 

 hand, give curves in which some portion of it at least remains when 

 the ventricle is no longer beating. It is for this reason that Morrow 

 is more inclined to attribute it to inflow and stasis. In cases of 

 heart block there is as a rule no " v " wave corresponding to the 

 purely auricular beats, but in a tracing of Wenckebach's a small 

 wave is seen. It is probable that both factors play a part in the 

 production of the wave under certain circumstances ; that with quick 

 filling of the auricle or sustained plateau the first will be prominent, 

 and that with slower filling and quicker heart beat the pressure in the 

 auricle will be low when the ventricle passes into diastole, and that 

 as a consequence the tricuspid valves will open later. Under these 

 circumstances the second factor may be the more pronounced. 



1 This movement of the auriculo-ventricular junction was described by Chauveau 

 in 1887 (Assoc. franq. p. I'avanc. d. Sc.), in a paper in which he gives a figure (No. 

 12), illustrating views very similar to those recently published by Keith. The 

 movement is fully discussed by Fredericq ( I2 *), and many other writers. 



2 Allowing the S.C. to A.O. instant at '04 to '06 sec., there is time for the 

 production of an appreciable wave. But this time interval is very difficult to 

 measure with any degree of accuracy, and it cannot be held that our estimates of 

 it are at present anything more than approximate. 



