432 



Scientific Proceedings (132) 



heart muscle itself, it is evident that they also depend on the 

 nature of the body tissue as a conducting medium. Thus, if 

 the body were composed of a non-conducting material, it is ob- 

 vious that the primary cardiac electrical effect would not give 

 rise to differences of potential in remote parts, while, on the other 

 hand, if the body possessed the property of a good conductor, 

 such as copper, it can be shown that the difference of potential 

 between parts remote from the heart would be infinitesimal. 



These considerations led us to believe that the presence of a 

 large effusion surrounding the heart, especially a large pericar- 

 dial effusion, might manifest itself by a lowering of the voltage 

 of the electrocardiogram. This belief has been reinforced by 

 our observation of seven cases of low voltage associated with 

 large pericardial or pleuropericardial effusions. In some of these 

 cases the markedly low voltage of the electrocardiogram led to 

 a suspicion of effusion, which was later confirmed by X-ray 

 examination, aspiration or autopsy finding. 



The characteristic finding in the electrocardiogram is a decided 

 lowering of voltage of the main deflection in all three leads. 

 This is not necessarily associated with any constant alteration in 

 the shape of the various waves, although it is quite conceivable 

 that the effusion may also alter the electrical axis of the heart in 

 some cases, or cause other changes in the propagation of the elec- 

 trical disturbance. 



It is possible that fairly large effusions may fail to effect 

 the voltage of the electrocardiogram appreciably in certain cases. 

 It is also quite true that some patients have electrocardiograms 

 with low voltage not associated with any effusion, e. g., cases 

 with myodegeneration. However the occurrence of the electro- 

 cardiographic finding in fairly constant association with an ef- 

 fusion and the fact that such a relation is to a certain extent pre- 

 dictable in advance, renders it significant and suggests further 

 clinical and experimental observation. 



