324 



Scientific Proceedings (130) 



lar systole and the phase of systolic ejection may offer a criterion 

 of ventricular efficiency as determined by auricular systole. 



Our attention was directed to this question in the course of an 

 investigation into the duration of ventricular systole in fibrilla- 

 tion of the auricles. Inasmuch as the venous pressures are con- 

 siderably increased in this condition, we anticipated, on the basis 

 of animal experiments, that the duration of systole and its ejec- 

 tion phase would be greater than in corresponding cycles of 

 normal hearts. Contrary to expectations, however, we found 

 that on the whole the length of total systole as well as the dura- 

 tion of the ejection phase was definitely shorter than normal. 

 This shortening was apparently unrelated to the age, blood pres- 

 sure, medication or etiology of the fibrillation. 



In attempting to explain this we were fortunate in finding a 

 patient in whom periods of auricular fibrillation alternated spon- 

 taneously with a normal mechanism, as established by electro- 

 cardiograms. Fortunate also was the fact that the heart rate 

 remained rapid during the periods of normal mechanism. This 

 permitted calculations at approximately the same heart rates. 



Results: The measurements of twenty-two beats during fibril- 

 lation of the auricles and of a like number during normal heart 

 action gave the figures shown in Table 1. They indicate that 



TABLE l. 



Cardiac 

 mechanism 



Predominant 

 heart rate 

 (beats per 

 min.) 



Duration of 

 preceding 

 diastole 

 (average) 



Duration of 

 total ven- 

 tricular 

 systole 

 (average) 



Duration of 

 systolic ejec- 

 tion phase 

 (average) 



Duration of 

 "systole" as 



calculated 

 from formula 



S — .S1VG 



Auricular 



fibrillation .... 

 Normal 



mechanism .. 



151 

 130 



0.222 sec. 

 0.234 sec. 



0.175 sec. 

 0.226 sec. 



0.128 sec. 

 0.171 sec. 



0.195 sec. 

 0.210 sec. 



under otherwise practically constant conditions the duration of 

 systolic ejection and total systole were shorter during the period 

 of auricular fibrillation than during the interval in which normal 

 auricular contractions were present. 



These effects can be interpreted in the following way — indeed, 

 as previously indicated, they can not be explained in any other 

 manner. During the synergic auricular contractions which occur 



