EFFECT OF ELECTRIC SHOCK ON HEART 



459 



fibrillation. The character of both post-shock electrocardiograms is 

 somewhat masked by higher frequency currents resulting from skeletal 

 muscle activity following the shock. However, the post-shock electro- 

 cardiogram of the group lA reveals the same typical sequence of 

 prominent deflections that appear before shock, while that of the 

 group IB shows an entirely different wave shape. The appearance 

 of this typical fibrillating wave and the absence of heart sounds fol- 

 lowing shock were taken as conclusive evidence of ventricular fi- 

 brillation. 



Threshold of Fibrillation 



The threshold current increases roughly with both the heart weight 

 and body weight of the different species of animals, although if the 

 three smaller species be considered alone this relationship does not 

 hold, their threshold currents being practically the same despite 

 widely different body weights. Data from tests on a number of 

 different species are summarized in Fig. 2. 

 0.4.81 — 



0.44 



0.40 



^0.36 



< 



jl.0.32 



Z 

 111 



q: 

 trO.28 



0.24. 



< 



^0.20 



1 



- 0. 12 



Z 



0.04 



O SHEEP A CALP 

 + PIG Q DOG 



/ 







A 



^~ 



A+ + + 



T 



^^ 



"7^ 



/ 



20 



30 40 50 60 70 



BODY WEIGHT -KILOGRAMS 



Fig. 2 — Relation of minimum current causing ventricular fibrillation to body 

 weight for different animal species. Shock duration 3 seconds. Frequency 60 

 cycles. Electrodes on right fore and left hind legs. (Averages shown by larger 

 symbols.) 



