ANALYSIS OF TRACES 



299 



a current is very rarely considered in routine clinical electro- 

 cardiography. 



The analysis of electrocardiograms is by no means simple. 



FIG. 66. Electrocardiogram from lead II. and Phono-cardiogram taken simul- 

 taneously from a normal subject. 



Considerable uncertainty exists as to the exact interpretation of 

 certain units in the trace. If Einthoven's symbols PQRST are 



FIG. 67. Similar records to above, but taken from a subject suffering from mitral 

 stenosis. The space between the first and second sound is filled by a coarse, loud, 

 diastolic murmur (M). 



used it is generally agreed that P is pre-systolic and that Q (positive 

 E.M.F.) indicates that the wave of contraction does not start at 

 the base of the ventricle but a short distance from it. R is no 



