126 
CARDIAC MODELS 
41 
DAYS 
Figure 8. — Effect of counterpulsation on arterial and 
coronary sinus lactate concentration in the ischemic 
heart. Mean findings of five experiments. 
treated dogs, within thirty minutes of counter- 
pulsation there was an increase in coronary 
flow to near normal levels. Reversed polarity 
observed coincidence with a sharp rise in cor- 
onary flow supports the concept of mechanically 
induced retrograde circulation. There appears 
to be a critical opening time of thirty minutes 
for potential collateral vessels. Beyond this 
time, counterpulsation failed to produce any 
additional benefit. The persistence of elevated 
coronary flow with reversed polarity long after 
cessation of pumping correlated with post- 
mortem angiographic patterns of retrograde 
circulation and with vinylite corrosion casts of 
coronary collateral circulation observed in an 
earlier study.^ 
With the onset of coronary insufficiency, 
lactate concentration rose in both the arterial 
and coronary sinus blood and the myocardium, 
instead of extracting lactate, began producing 
it (Experiment III). This was reflected in ele- 
vated concentrations of lactate in coronary sinus 
blood and the development of a positive excess 
lactate. However, following counterpulsation, 
there was a decline in lactate concentration in 
both the coronary sinus and arterial blood, but 
the coronary sinus lactate concentration was 
lower in the arterial sample, suggesting that 
normal oxidative metabolism was restored and 
providing additional evidence of increased myo- 
cardial perfusion. 
Prolonged survival of treated animals can 
therefore be correlated with restoration of near 
normal perfusion to ischemic myocardium. It is 
undoubtedly related to prevention or restriction 
of the extent of myocardial infarction, the re- 
duction of myocardial irritability and the re- 
turn of normal myocardial oxidative metabolism 
and ventricular function. 
STUDY II 
This study was designed to evaluate the ef- 
fect of three different methods of counterpulsa- 
tion on circulatory dynamics and metabolism in 
acute cardiogenic shock. Adult mongrel dogs 
were used and a technique of serial coronary 
artery branch ligation was selected as the 
method for producing acute cardiogenic shock. 
The animals were divided into a control group 
and three different treatment groups. The dogs 
were all subjected to a left thoracotomy and 
placement of appropriate flow probes and can- 
nulas for monitoring hemodynamic parameters 
and blood sampling (Figure 9A). The electro- 
cardiogram, aortic pressure, left atrial pres- 
sure, cardiac output and coronary blood flow 
were monitored throughout each experiment. 
Serial determinations of arterial oxygen and 
lactate concentration were also obtained. In 
Groups 1 and 2, the coronary sinus lactate con- 
centration and in Groups 3 and 4, the plasma 
hemoglobin concentration and hourly urine out- 
put were determined. 
In the control group, once cardiogenic shock 
was induced, no treatment was administered 
and the animals were followed closely until 
death. However, in the three treatment groups, 
counterpulsation was instituted when cardio- 
genic shock became manifest. At the termina- 
tion of each experiment, autopsy examination 
was carried out after death or sacrifice. 
Cardiogenic Shock Model 
Progressive left ventricular failure was pro- 
duced by serial ligation of branches of the an- 
terior descending and left circumflex coronary 
arteries. The branches were ligated at their 
origin as illustrated in Figure 9B. Usually, 
cardiogenic shock did not develop unless the 
two major diagonal branches of the anterior 
descending, the marginal artery and one or two 
proximal smaller branches of the left circum- 
