122 
CARDIAC MODELS 
Dog No. 
215 
Dog No. 
219 
velop immediately, but was apparent within 
thirty minutes. Coincident with the rise in cor- 
onary flow, there was reversal of polarity indi- 
cating reversal of direction of blood flow 
(Figure 4). After cessation of pumping, the 
increased flow with reversed polarity persisted. 
The flow subsequently diminished gradually 
over several days, eventually stabilizing at an 
average of 89 percent of initial reading. Histo- 
grams comparing the findings in control and 
counterpulsated dogs are presented in Figure 
5. 
All untreated control animals died a sudden 
(presumably arrhythmic) death between thirty 
and thirty-six days after placement of con- 
strictors. None of the counterpulsated dogs 
died, but were sacrificed between the thirtieth 
and thirty-sixth day. Similar mean coronary 
artery constriction was found at autopsy in 
Dog No. 
223 
Un CIWCUMf LEX COWONAITf AKTWY FLOW 
DOG No. 22 isHTIAL FLOW 90 ex. 
Figure 3. — Angiograms of counterpulsated dogs re- 
vealing (a) retrograde filling on the left coronary 
artery branches by injection of the right coronary 
artery. Injection of the left coronary artery (b) re- 
veals marked homocoronary collateral circulation 
from prominent septal and anterior diagonal left 
ventricular branches arising proximal to the con- 
strictors. 
Experiment II 
Following placement of constrictors, there 
was progressive fall in coronary flow, most 
marked in the first ten days. In control animals, 
the flow fell to an average of 50 percent of 
initial reading by the fourteenth day, with little 
drop thereafter, despite increasing proximal 
stenosis (Figure 7). At the final determination 
prior to death, the flow averaged 41 percent. 
Coronary flow increased after the fourteenth 
day in only one animal and the rise was minimal. 
In treated animals, a mean drop in coronary 
flow to 50 percent on the fourteenth day was 
also observed, but counterpulsation produced 
dramatic restoration to normal or slightly above 
initial levels (Figure 8). The rise did not de- 
Pr« count*rpulKitien(t4rf) 
(imm«diat«iy) 
4 
During count*rpulsation 
(40 mimrtM) 
90cc 
counterpulsation 
(24 hours) 
80c<. 
Figure 4. — Flow tracing demonstrating increased flow 
after forty minutes of counterpulsation. Amplitude of 
flow during diastole is increased and the polarity is 
reversed. 
