134 
CARDIAC MODELS 
bMH/min. 
I60. 
I40. 
I20. 
too. 
HEART RATE 
ISO. 
no. 
1 2 3 
(hours) 
AORTIC PRESSURE 
70. 
\ 
\ 
\ 
1 **»/::::::. 
1 2 
(hours) 
LEFT VENTRICULAR WORK 
mmifg 
15. 
10. 
LEFT ATRIAL PRESSURE 
5. 
1 2 
(hours) 
CORONARY FLOW 
mm.Hg 
150_ 
125. 
3 4 
ARTERIAL OXYGEN TENSION 
too. 
1 2 
(hours) 
" I I 
2.6. 
2.4. 
20. 
1.6. 
1.2. 
CARDIAC OUTPUT 
Dyn*sAm./M<.~S 
2400. 
WOO. 
1 2 3 4 5 
(hours) 
PERIPHERAL VASCULAR RESISTANCE 
Figure 15. — Graphs illustrating the effects upon hemodynamics anci metabolism observed in 
animals treated by intra-aortic balloon counterpulsation. Mean findings in six dogs. 
critical closing pressure and therefore incre- 
ments as little as 10 mm. Hg. can produce a 
significant rise in coronary flow. 
SUMMARY 
Chronic coronary insufficiency produced by 
progressive proximal stenosis by ameroid con- 
strictors results in a reproducible state of sig- 
nificant myocardial ischemia. In the models de- 
scribed, flow in the anterior descending and 
circumflex coronary arteries decline by 50% 
within fourteen days, with minimal reduction 
thereafter, despite continuing proximal steno- 
sis. This preparation vividly demonstrates the 
natural potential for development of collateral 
circulation and therefore served as a desirable 
model for evaluating the effects of counterpul- 
sation. As indicated in the results, retrograde 
coronary flow could be significantly augmented 
which correlated with angiographic findings, 
restoration of myocardial aerobic metabolism, 
lesser incidence of myocardial infarction and 
prolonged survival. 
The technique of serial ligation of branches 
of the anterior descending and circumflex cor- 
onary arteries resulted in increasingly severe 
left heart failure ultimately manifesting as 
cardiogenic shock. There was no significant 
difference in the time interval between initial 
ligation and the onset of shock. Untreated, con- 
trol animals died wthin 135 minutes from pro- 
gressive left ventricular failure and terminal 
ventricular fibrillation. This time interval was 
sufficient for evaluating three different modali- 
ties for counterpulsation in treatment groups 
and determining the advantages and limitations 
of the various methods for circulatory support. 
REFERENCES 
1. LiTVAK, J. and Vineberg, A.: Experimental grad- 
ual arterial occlusions with in vitro and in vivo 
observations, Surg. 46:953, 1959. 
2. RoBBiNS, S. L., Solomon, M. and Bennett, A.: 
