BOWIE, PUROHIT, ADAMS, SOMAIAH, HAWTHORNE AND HINDS 545 
Table I. — Cardiovascular Control Measurements in Anesthetized Horses 
Cardiac 
Ejection 
Horse No. 
End-Diastolic 
End-Systolic 
Stroke 
Heart Rate 
Output 
Fraction 
Stroke Work 
Volume (ml) 
Volume (ml) 
Volume (ml) 
(beats/min) 
(L/min) 
(% EDV) 
(Gm-meters) 
014 
782.1 
413.5 
368.6 
97 
34.7 
47.2 
371.2 
017 
1127.7 
645.0 
482.6 
71 
34.4 
42.5 
395.2 
018 
688.5 
420.9 
267.6 
68 
18.2 
38.5 
224.0 
019 
811.2 
512.7 
298.5 
60 
17.3 
33.8 
276.5 
022 
1082.1 
699.1 
383.0 
60 
23.1 
34.7 
327.3 
0001 
1114.7 
816.7 
298.0 
86 
25.9 
26.7 
274.0 
0008 
1566.5 
1300.3 
247.2 
54 
13.3 
15.8 
185.6 
UU14 
1116.2 
760.2 
356.0 
83 
29.7 
35.4 
OQf\ A 
zyu.4 
0016 
756.2 
493.5 
262.6 
72 
18.9 
34.8 
223.0 
0018 
756.6 
405.7 
360.9 
67 
23.5 
46.4 
276.6 
0019 
831.2 
479.3 
298.6 
60 
17.2 
31.8 
296.4 
0020 
1189.0 
1044.5 
144.3 
94 
13.6 
12.2 
111.7 
Mean 
987.4 
669.7 
312.1 
72 
22.1 
32.8 
271.7 
S.E. ± 
70.5 
73.9 
23.2 
4 
2.0 
2.7 
21.5 
17- 
16 
o 
o 
kI5 
d 
u 
I 14 
> 
Q 
Ul 
>I3 
12 
8 12 16 
LVEDP - mm. Hg 
20 24 26 
Figure 4. — Left ventricular pressure volume relation-, 
ship due to rapid infusion of Tyrode's solution; 
whereas LVEDP = Left ventricular end diastolic 
pressure and LVEDV = Left ventricular end dias- 
tolic volume. 
left ventricle the left ventricular EDV, ESV, SV, 
EF, SW and CO were determined prior to and 
during the rapid intravenous infusion of Ty- 
rode's solution. Rapid infusion of Tyrode's solu- 
tion produced increases in EDV, SV, EF, SW 
and CO. The increase in cardiac output was 
mainly due to an increased stroke volume, since 
the heart rate was virtually unchanged. Bishop 
et aU^ have demonstrated that in conscious 
dogs, the rapid infusion of Tyrode's solution, 
results both in increases in heart rate and 
stroke volume. The present study in horses sug- 
gests that the elevation in stroke volume was 
due to an increase in the end-diastolic size of 
the ventricle evoking a Frank-Starling re- 
sponse. 
Ventricular function curves were plotted 
from the data derived from the rapid infusion 
of the Tyrode's solution. The relationship of left 
ventricular end-diastolic pressure (LVEDP) to 
left ventricular end-diastolic volume (LVEDV) 
is illustrated in Figure 4. The increase in end- 
diastolic volume was associated with a curve- 
linear increase in the end-diastolic pressure. The 
contour of the curve depicted here is similar to 
that which has been obtained on dogs by Tsak- 
iris et al.^'' The relation of left ventricular 
end-diastolic volume and the stroke work is il- 
I2h 
o 
o 
- II 
0) 
10- 
""9 
CO 
58 
> 
12 13 14 15 16 
LVEDV- cc. xioo 
17 
Figure 5. — Relationship of left ventricular end dias- 
tolic volume (LVEDV) and the left ventricular 
stroke work (LVSW) as a result of the rapid infu- 
sion of Tyrode's solution. 
