POLYSPHYGMOGRAMS 



277 



A tracing showing a higher degree of heart-block is given in Fig. 100. 



Sinus Arrhythmia. In this condition the radial pulse is markedly 

 irregular, but the "a," "c" and "v" waves of the jugular tracing occur 

 with the usual time relationship to one another, and there is no delay 

 in the "a"-"c" interval. 



X V X. X \ x \ 



Fig. 99. Delayed conduction time. First stage of heart-block. The A-C intervals measure more 

 than 0.2 second. (From K. P. Carter.) 



Sinus Bradycardia. The beat originates at long intervals in the 

 sinus; the "a-c" interval is normal, and the radial pulse very slow but 

 practically regular. 



Premature Beats. These may be either ventricular or auricular in 

 origin. In the former case the "a" waves on the jugular tracing space 

 regularly throughout, but the "c" waves at the point of disturbance 



>-<^ _\ 



r r i i i i IT 



\ \ \ ^V \ \ V 



Fig. 100. Dropped beats. Second stage of heart-block. (From F^. P. Carter.) 



coincide with the "a" waves, giving therefore a more pronounced wave. 

 This is due to a premature contraction of the ventricle occurring about 

 the time of the "a" wave, so that the latter finds the ventricle in a re- 

 fractory state (see page 178). The premature contraction is therefore 

 followed by a compensatory pause, which is evident on the tracing. An 

 example of such a case is given in Fig. 101. In doubtful cases the exact 



