F. KRAFT-HUNTER AND E, W. HAWTHORNE 
Table I. — Changes with Ventricular Pacing (Dog # 132 11th P.O. Day)'- 
639 
TCL LVEDP EDV SW Peak Mean (EJ) Aver. WF(EJ) Mean (EJ) 
N (msec) (mm Hg) (ml) (gm-m) dP/dt LVP (gms) VCF 
(mm Hg/sec) (mm Hg) (Cm/sec) 
Control Study 
14 
510 
34 
15 
5 
52 
3 
50 ± 4 
3860 
157 
140 
-4- 
4 
1832 
89 
30.4 
2 
14 
488 
53 
9 
4 
47 
•+- 
5 
44 ± 6 
3896 
300 
138 
6 
1786 
124 
27.6 
3 
31 
**368 
— 
12 
6 
— 
2 
39 
2 
27 ± 3 
3766 
136 
116 
— 
5 
1268 
— 
95 
33.4 
0 
25 
•*314 
— 
3 
5 
— 
3 
37 
-f- 
1 
24 ± 1 
3638 
82 
120 
— 
2 
1303 
— 
34 
30.8 
— 
1 
31 
•*269 
4 
5 
■+■ 
4 
33 
-f- 
2 
23 ± 3 
4102 
-4- 
363 
128 
— 
9 
1370 
— 
137 
29.8 
— 
2 
Norepinephrine 
(0.4 mgms/Kg/min) 
10 
714 
79 
16 
-4- 
2 
57 
•+■ 
3 
67 ± 7 
6452 
-^- 
277 
161 
8 
1924 
122 
42.9 
2 
13 
628 
125 
15 
± 
3 
58 
-+- 
2 
70 ± 10 
6826 
■+- 
257 
164 
9 
2020 
222 
43.6 
3 
22 
**366 
3 
17 
-+- 
4 
58 
3 
68 ± 6 
8698 
242 
214 
5 
2885 
129 
39.2 
3 
30 
**311 
7 
11 
3 
51 
2 
61 ± 4 
9026 
324 
189 
-+- 
5 
2275 
74 
46.8 
2 
30 
**265 
3 
6 
4 
42 
3 
49 ± 3 
Propranolol 
8450 
362 
177 
4 
1929 
75 
46.5 
-4- 
3 
(0.5 mgms/Kg) 
12 
5G0 
19 
14 
-+- 
2 
60 
-t- 
1 
50 ± 3 
3159 
61 
134 
3 
2050 
80 
26.1 
1 
12 
533 
16 
14 
2 
56 
2 
48 ± 3 
3178 
-»- 
49 
132 
4 
1958 
83 
25.9 
1 
20 
•*364 
2 
11 
-^- 
2 
52 
± 
1 
31 ± 2 
3110 
-t- 
79 
126 
2 
1741 
44 
29.2 
1 
30 
*»309 
3 
9 
-+- 
3 
51 
1 
28 ± 3 
3143 
109 
122 
4 
1713 
78 
27.4 
2 
30 
**268 
3 
11 
-4- 
2 
48 
3 
26 ± 6 
3338 
221 
127 
4 
1788 
86 
24.7 
3 
* Shown above are the effects of ventricular pacing of a conscious dog 11 days after surgery for instrumentation. Consecutive cardiac cycles 
were analyzed for periods of sinus rhythm and while the left ventricle was paced at various rates. The observations were made during a 
control period, during the steady state while infusing norepinephrine, and after subsequent intravenous injections of propranolol. The results 
are typical for the group of dogs studied. N = the total number of consecutive cardiac cycles analyzed in each sample; TCL = total cycle 
length; LVEDP = left ventricular end-diastolic pressure; EDV — end-diastolic volume; SW = stroke work; mean LVP (EJ) = average left 
ventricular pressure during ejection; Aver. WF(EJ) = average wall force during ejection; mean Vcf = average velocity of internal cir- 
cumferential shortening rate during ejection. AH values are mean ± SD. 
'•'Ventricle paced. 
decreases ventricular volume in conscious dogs. 
This observation was fully investigated by 
Rushmer and associates'^. Since left ventricular 
pacing at rates from 2 to 8.5 Hz causes stepwise 
decreases in ventricular volume and stroke 
work without significantly altering myocardial 
contractility, it appears that an acceptable ven- 
Table II. — A Comparison of Atrial and Ventricular 
Pacing (Dog #132 11th P.O. Day) 
Mean* Peak Mean** 
TCL LVP Aver. WF* dP/dt VCF 
N (msec) (mm Hg) (gm-m) (mm Hg/sec) (Cm/sec) 
Left Atrial Pacing (P) 
(SW = 
-9.65 + EDV X 1.13) 
9 
748 
160 
129 ± 6 
1703 ± 95 
3792 ± 
126 
28.3 
1 
12 
753 
154 
131 ± 6 
1734 ± 108 
3819 ± 
106 
28.7 
1 
22 
P376 
8 
141 ± 8 
1611 ± 67 
5258 ± 
321 
33.7 
3 
27 
P338 
51 
139 ± 6 
1539 ± 89 
4469 ± 
522 
33.0 
5 
30 
P288 
43 
125 ± 6 
1261 ± 59 
4294 ± 
605 
33.0 
6 
Left Ventricular Pacing 
(V) 
(SW = - 
-31.5 + EDV 
X 1.55) 
14 
510 
34 
140 ± 4 
1832 ± 89 
3860 ± 
157 
30.4 
2 
14 
448 
53 
138 ± 6 
1786 ± 124 
3896 ± 
300 
27.6 
3 
21 
V368 
12 
116 ± 5 
1268 ± 95 
3766 ± 
136 
33.4 
2 
25 
V314 
3 
120 ± 2 
1303 ± 34 
3638 ± 
82 
30.8 
1 
31 
V269 
4 
128 ± 9 
1370 ± 138 
4102 ± 
364 
29.8 
2 
* — During ejection 
** = Endocardial surface 
All values are mean ± SD 
tricular function curve can be constructed from 
these data. The function curve shifts upward 
and to the left under conditions of increased 
myocardial contractility. A shift downward and 
to the right is produced with depression of ven- 
tricular function. These shifts are consistent 
with and as predicted by the classical studies of 
Sarnoff and his associates. It therefore appears 
that left ventricular pacing in conscious instru- 
mented dogs is a reliable means of producing a 
spectrum of end-diastolic volumes for acquiring 
the primary information necessary to study the 
shifts in the stroke work/end-diastolic volume 
relation with changes in ventricular function 
brought on by various interventions. Analysis 
of function curves produced by either atrial 
or sequential pacing as compared to those 
produced by left ventricular pacing shows that 
with atrial or sequential pacing for any given 
end-diastolic volume the stroke work produced 
is greater than with ventricular pacing. Our 
studies suggest that this difference is due largely 
to the increased contractility at each pacing 
rate that occurs with atrial or sequential pac- 
ing. No evidence is provided to determine 
whether or not the aberrant ventricular my- 
