EFFECT OF ELECTRIC SHOCK ON HEART 



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RATIO OF DURATION OF SHOCK TO LENGTH OF HEART BEAT 



Fig. 5 — Effect of duration on threshold. 



is, however, not believed that increasing the duration beyond 3 seconds 

 would reduce the average threshold current appreciably below 0.25 

 ampere. 



X'entricular fibrillation has been found to be the only serious cardiac 

 effect of the currents applied in these tests; however, temporary dis- 

 ruptions of normal cardiac activity frequently can be observed. A 

 most common effect of electric shock is a change in heart rate. Elec- 

 trocardiograms after shock frequently indicate disturbances of con- 

 duction in the heart. Premature heart beats (extrasystoles) and 

 fibrillation of the auricles have also been observed. 



The persistence of any of these conditions for more than a few 

 minutes is rare. There is no evidence of any cardiac abnormalities or 

 the presence of cardiac damage in electrocardiograms taken at intervals 

 up to two months following shocks which did not immediately cause 

 death. 



Effect of High Currents 



There was evidence from the work of Prevost and Battelli and some 

 of the early results of this investigation that the stimulus of a powerful 

 current would be less liable to cause fibrillation than a current moder- 

 ately above the threshold. To test such evidence repeated short 

 shocks of 23 to 26 amperes were given to a group of sheep in the 

 sensitive phase of their cardiac cycle. Ten survived 5 shocks each 

 without fibrillation, while an eleventh fibrillated on the initial shock. 

 Each of the 10 surviving sheep was given additional similar shocks, 



