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HANDBOOK OF PHYSIOLOGY 



CIRCULATION 



traction descent; b) increased duration of the left 

 auricular contraction descent; c) decreased fall of the 

 curve during the rapid filling phase (less than the 

 auricular contraction descent); d) steeper rise in the 

 curve during the reduced ejection phase. 



Even when objectively measurable parts of the 

 curve (the duration of the auricular contraction 

 descent) did not exhibit clearly pathologic values, the 

 curve as a whole had a characteristic appearance that 

 was encountered only in mitral stenosis. 



In mitral incompetence characteristic changes were 

 recorded in the electrokymographic curves from the 

 left auricle. These changes consisted of an earlier 

 steeper rise than ordinary during the ejection phase. 

 In addition, the curves in pure incompetence showed 

 a notably great fall during the rapid filling phase. 

 These curves agreed fully with the pressure and 

 volume curves obtained in experimentally induced 

 mitral incompetence by Wiggers & Fell (204). 

 Fleischner et al. (74) studied the atrial electrokymo- 

 gram in 5 normal subjects and in 15 patients with 

 rheumatic mitral valvular disease. They also found 

 that only with the utmost careful evaluation of the 

 tracings was it possible to diagnose stenosis and judge 

 the degree of regurgitation. The differentiation be- 

 tween stenosis and incompetence was almost com- 

 plete in patients with normal sinus rhythm, whereas 

 in patients with atrial fibrillation tracings sometimes 

 were obtained suggesting mitral incompetence where 

 surgical exploration did not reveal other lesions than 

 stenosis. 



In studies of the normal right atrial electrokymo- 

 gram Rudhe (172) found a good correlation between 

 the pressure event in the atrium and the movement of 

 the border of the right atrial shadow. Of special inter- 

 est was the delay of movement of the wall in compari- 

 son to the rise of pressure during atrial systole, on the 

 average 0.04 sec (range 0.02 to 0.06 sec, 13 cases). 

 A similar delay was registered between the c wave 

 in the pressure curve and the corresponding notch in 

 the volume curve. Rudhe thought it probable that the 

 initial displacement of the blood during atrial con- 

 traction takes place under acceleration, owing to the 

 inertia of the blood mass. This implies that emptying 

 is inappreciable in the earliest part of atrial systole. 

 A further implication of the phase difference between 

 the atrial pressure and the volume increase in the 

 ventricle is that the maximum blood displacement is 

 reached after the maximum rise in atrial pressure. 

 This is also evident from experimental \vork by Wig- 

 gers. 



Angiocardiography 



Arvidsson (7) studied the changes of left atrial 

 \olume calculated from serially exposed biplane films 

 during angiocardiography. He found in mitral ste- 

 nosis that the maximum volume of the left atrium was 

 between 75 and 265 ml, averaging 145 ml (18 cases of 

 mitral stenosis in sinus rhythm). The volume varia- 

 tions during the cardiac cycle lay in most cases 

 between 20 and 50 ml, the average being 35 ml. In i 7 

 cases with sinus rhythm the changes in left atrial 

 volume during the cardiac cycle were plotted. All the 

 curves had approximately the same appearance in 

 the.se cases. The maximum volume was recorded at 

 the end of systole. During early diastole there was a 

 fairly small decrease in volume. Before the atrial 

 contraction there occurred either a plateau on the 

 curve or, in some cases, a volume increase. A con- 

 spicuous decrease in volume took place during atrial 

 systole, and this decrease continued in most cases 

 beyond the QRS complex in the electrocardiogram. 



In mitral stenosis with atrial fibrillation the maxi- 

 mum atrial volume varied from 1 50 to 400 ml, with 

 the average at 230 ml. The volume variations in this 

 group did not exceed 20 ml, the average being 16 ml. 

 It was not possible to construct a left atrial volume 

 curve but it was possible to register how the \entricu- 

 lar rate influenced the filling of the left ventricle. 

 When ventricular contractions occurred in close 

 succession, the atriuin did not have time to empty, 

 and this was reflected in an increased volume. When 

 the intervals between ventricular systoles were longer, 

 more effective filling of the ventricle was attained; 

 this was reflected in an appreciable decrease in the 

 volume of the atrium. In predominant mitral insuffi- 

 ciency with sinus rhythm the maximum volume of the 

 atrium was between 120 and 200 ml, the average 

 being 155 ml. The changes in maximum volume 

 varied from 70 to 150 ml, with the average at 80 ml. 



A left atrial volume curve could be constructed for 

 eight cases. The volume curve was characterized by a 

 rapid increase in volume during systole, which began 

 before or in connection with the QRS complex. The 

 maximum \olume occurred near the close of systole. 

 In early diastole there was a rapid \olume decrease 

 which diminished during diastasis, and in a few cases 

 a volume increase occurred immediately before atrial 

 systole. The decrease in \olumc din-ing atrial systole 

 was relatively small. In predominant mitral insuffi- 

 ciency with fibrillation the maximum volume of the 

 atrium varied from 610 to 980 ml, with the average 

 at 770 ml; and the volume variations from 1 10 to 140 



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