L. N. COTHRAN, E. W. HAWTHORNE AND H. SANDLER 
561 
2.0 2.1 
INT. RADIUS 
Figure 11. — The relationship between the internal axis 
ratio and internal radius of the left ventricle during 
ejection for the group of dogs studied. 
electronic integration of the aortic flow curve. 
In each case, the calculated stroke volume 
closely approximated the actual value. The 
stroke volume obtained by assuming a constant 
axis ratio during ejection (triangles) overesti- 
mated the actual stroke volume (9.7%) while 
the value obtained by a point-to-point calcula- 
tion of the axis ratio using equation 5, lies 
slightly below the true stroke volume (3.5%). 
DISCUSSION 
The dimensional changes accompanying con- 
traction of the left ventricle were determined 
by the direct application of transducing devices 
to the heart and by the combined use of biplane 
cineradiographic and analog techniques. The 
phasic pattern of left ventricular dimensional 
changes demonstrated in the present study are 
consistent with the findings of other 
too- 
S 80. 
; 60 
\ 40 
20H 
0' 
EF.344 EF.382 EF .430 EF .417 EF .34t 
EDV 
EDV 
EDV 
EDV 
sv 
SV 
SV 
SV 
SV 
ESV 
ESV 
ESV 
ESV 
ESV 
EDV 
DDG ) 2 3 4 S 
Figure 12. — Left ventricular volumes at end-diastole 
(EDV) and end-systole (ESV) for the group of dogs 
studied. (SV) stroke volume, (EF) ejected fraction. 
- 20 
INTERNAL RADIUS (cm) 
Figure 13. — A graph showing the linear relationship 
between stroke volume and the internal radius of the 
left ventricle. 
investigators.^'i<^-i*'-i^ But, an attempt was 
made here to record simultaneously, the exter- 
nal, internal and transmural dimensional 
changes and to apply these data to estimates of 
myocardial stress and chamber volume. The 
equations used to calculate left ventricular 
stress and chamber volume are based upon the 
assumptions that the changes recorded in wall 
thickness were representative of the ring of 
muscle underlying the dimension gages and that 
Z 20- 
Figure 14. — Stroke volumes estimated using a constant 
axis ratio (A), a calculated axie ratio (O) and the 
curve obtained by electronic intergration of the aortic 
flow signal (•). 
