CANINE CORONARY INSUFFICIENCY MODELS FOR 
EVALUATING SYSTEMS FOR CIRCULATORY SUPPORT* 
J. Rosensweig and S. Chatterjee* 
Canine experimental models of coronary insufficiency- 
will be described. Acute and chronic models were uti- 
lized in studying effects of counterpulsation on coronary 
collateral circulation, circulatory dynamics, myocardial 
function and survival. 
Chronic insufficiency models were created by place- 
ment of ameroid constrictors about the origin of left 
coronary arteries. The predominant left coronary circu- 
lation in dogs makes this preparation a rather severe 
test of potential collaterals. Within 14 days, flow de- 
clined to 49% with little reduction thereafter despite 
continuing proximal stenosis. A reproducible state of 
stable coronary insufficiency was achieved which facil- 
itated assessment of counterpulsation-induced collateral 
circulation. Within one hour, retrograde flow could be 
demonstrated which correlated with angiographic find- 
ings, restoration of myocardial oxidative metabolism, 
reduced incidence of fatal arrhythmia and myocardial 
infarction and prolonged survival. 
Acute insufficiency models, produced by serial ligation 
of branches of the anterior descending and circumflex 
arteries, were used to induce cardiogenic shock. Shock 
was characterized by sustained elevation of left atrial 
pressure above 12 mm. Hg., reduction of cardiac output 
by at least 40% and a 30% or more fall in aortic systolic 
pressure. Untreated, the animals died from progressive 
left ventricular failure and fibrillation within 135 
minutes. This interval allowed sufficient time for insti- 
tution of circulatory support by counterpulsation and 
permitted study of three different modalities — arterio- 
arterial counterpulsation, intra-aortic balloon pumping 
and venoarterial bypass with oxygenation and diastolic 
augmentation. The acute model served effectively to 
indicate the advantages and limitations of each form of 
therapy. 
INTRODUCTION 
Experimental canine models were used to in- 
vestigate effects of counterpulsation in chronic 
coronary insufficiency and acute cardiogenic 
shock. These models were readily reproducible 
and closely simulated corresponding clinical 
situations. 
*Lady Davis Institute For Medical Research, Jewish General 
Hospital, Montreal, Canada 
Present address, Departments of Surgery, University of Connecticut 
School of Medicine and Mount Sinai Hospital, Hartford, Connecticut 
06112. 
STUDY I 
This study was designed to evaluate counter- 
pulsation-induced collateral circulation, in re- 
lation to survival, coronary flow and myocardial 
metabolism. Three different experiments were 
carried out utilizing the chronic coronary insuf- 
ficiency preparation initially described by Lit- 
vak and Vineberg.^ In each experiment, counter- 
pulsation was carried out for one hour on the 
14th day, a time corresponding to the develop- 
ment of at least 50% luminal constriction — i.e. 
critical coronary artery stenosis. Arterio- 
arterial counterpulsation using the Simas pump 
was instituted by cannulation of the femoral 
artery (Figure lA). The aspiration phase of 
the pressure pulse generator was begun in pre- 
systole and continued throughout systole. Blood 
was returned to the arterial circulation during 
diastole. Pump stroke volume of 10-15 cc. 
achieved the desired alteration in aortic pres- 
sure configuration. 
Experiment I — Survival Study 
Twenty-four adult mongrel dogs were oper- 
ated upon, half serving as control. By left 
thoracotomy, chronic progressive coronary in- 
sufficiency was induced by application of a 
paraffin coated formalized casein (ameroid) 
constrictor 2.77 mm. I.D. about the origin of 
the anterior descending artery (just distal to 
the takeoff of the septal artery) and about the 
origin of the circumflex branch of the left cor- 
onary artery (Figure 2). 
Following placement of constrictors, the ani- 
mals were allowed to recover. Dogs in the 
treated group were subsequently counterpul- 
sated on the 14th day. All animals were followed 
until death, but long-term survivors were sacri- 
ficed after 90 days. At autopsy, the degree of 
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