560 
HEMODYNAMICS 
Table III. — Changes in Left Ventricular Axes During the Cardiac Cycle 
Dog 
Major Semi-Axis 
(cm) 
Minor Semi-Axis 
(cm) 
Axis Ratio 
(ED) 
(EIVC) 
(ES) 
(ED) 
(EIVC) 
(ES) 
(ED) 
(EIVC) 
(ES) 
1 
3.58 
3.81 
3.50 
2.39 
2.31 
1.96 
1.50 
1.65 
1.79 
2 
3.66 
3.70 
3.53 
2.38 
2.31 
1.95 
1.54 
1.61 
1.85 
3 
3.57 
3.73 
3.63 
2.38 
2.30 
1.80 
1.50 
1.62 
1.96 
4 
3.82 
3.89 
3.67 
2.60 
2.37 
1.84 
1.53 
1.64 
1.94 
5 
2.44 
2.37 
1.94 
6 
3.70 
3.83 
3.65 
2.33 
2.28 
1.91 
1.58 
1.68 
1.86 
7 
2.24 
2.17 
1.84 
8 
2.11 
1.95 
1.60 
9 
2.09 
2.01 
1.66 
10 
2.46 
2.38 
1.98 
Av. 
3.67 
3.79 
3.56 
2.33 
2.24 
1.84 
1.53 
1.64 
1.88 
Key: 
(ED) end-diastole, (EIVC) end-isovolumic contraction. 
(ES) end-systole. 
Table 
IV. — Left Ventricular 
Pressures and Myocardial Stresses During 
the Cardiac Cycle 
Dog 
L. V. Pressure 
(Gm/Cm=) 
Av. Meridional Stress 
(Gm/Cm=) 
Av. Hoop Stress 
(Gm/Cm2) 
(EIVC) 
(APVP) 
(ES) 
(EIVC) 
(APVP) 
(ES) 
(EIVC) 
(APVP) 
(ES) 
1 
120.0 
155.0 
53.5 
122.9 
136.6 
33.8 
224.8 
254.1 
68.2 
2 
128.5 
170.0 
51.3 
133.0 
127.6 
31.3 
242.5 
245.6 
63.8 
3 
119.7 
179.5 
59.8 
116.3 
148.1 
26.8 
211.9 
265.0 
59.8 
4 
106.3 
158.8 
63.9 
121.3 
99.3 
35.1 
217.7 
209.7 
76.5 
5 
123.8 
172.7 
62.6 
168.6 
216.8 
40.1 
6 
122.4 
172.7 
54.4 
122.6 
167.0 
33.3 
215.4 
312.6 
56.6 
7 
122.4 
136.0 
61.2 
117.8 
108.3 
33.3 
8 
140.1 
150.0 
68.1 
64.3 
71.4 
27.0 
9 
97.9 
149.9 
69.4 
90.6 
66.1 
26.1 
10 
129.2 
163.2 
61.2 
119.0 
141.1 
29.8 
Av. 
121.0 
160.8 
60.5 
117.6 
128.3 
25.6 
222.5 
257.4 
65.0 
Key: (EIVC) end-isovolumic contraction, (APVP) at peak ventricular pressure, (ES) end-systole. 
oid (eq. 4) and used a value for axis ratio 
which was calculated from the equation describ- 
ing the linear relationship between axis ratio 
and internal radius (eq. 5) . This was done at 20 
msec intervals throughout ejection. In addition, 
300 
200 
100 
0 40 
80 120 160 200 240 280 
It Sic 
Figure 9. — The time course of left ventricular stresses 
and pressure. (X) hoop stress, (A) meridional stress, 
(O) left ventricular pressure. 
similar calculations of volume were made where 
the end-diastolic axis ratio was determined and 
used as a constant in the moment-to-moment es- 
timations. The results for a typical experiment 
are shown in Figure 14. The actual change in 
stroke volume (closed circles) was obtained by 
A Am lilii (1 
■ *|>1 Rllii II 111 liliii 
0 40 60 80 100 
19 2 0 2.1 2.2 2 3 
Figure 10. — (A) The time course of the left ventricular 
internal axis ration during ventricular systole. (B) 
The relationship between internal axis ratio and in- 
ternal transverse radius during ejection. 
