J. ROSENWEIG AND S. CHATTERJEE 
131 
NORMAL 
ON PUMP 
:f4 
Figure 12. — Electrocardiographic and aortic pressure tracings in a normal dog. During synchronized pulsa- 
tile venoarterial bypass with oxygenation systolic pressure is reduced and diastolic pressure is 
markedly elevated. 
reduction of pressure volume work of the heart 
by 50%. 
In untreated control animals, myocardial is- 
chemia impaired cardiac function and pro- 
duced severe lactic acidosis which further 
aggravated myocardial irritability and con- 
tractility. Progressive left heart failure devel- 
oped and death from ventricular fibrillation 
ensued. These findings are similar to those re- 
ported with other cardiogenic shock prepara- 
tions. However, contrary to the observations of 
Agress and Associates, who noted peripheral 
vasodilation, ^"'1" all animals demonstrated in- 
creased peripheral vascular resistance when 
shock developed. Whereas untreated dogs died 
within one and half hours of onset of the shock 
state, dogs treated by circulatory support sur- 
vived the experimental period (irrespective of 
the mode of therapy). Synchronous circulatory 
assistance prevented fatal arrhythmia and en- 
abled the animals to survive the ischemic epi- 
sode. 
The results of arterio-arterial counterpulsa- 
tion are in accord with the findings of Jacoby,^^ 
Goldfarb,!^ Mantini,!^ and Kishi.-'^ Peripheral 
vascular resistance was diminished and left ven- 
tricular work reduced by 39 . Although ob- 
viously helpful, it is doubtful whether only one 
hour of assisted circulation could have by itself 
produced sustained improvement of circulation 
following cessation of pumping. The findings 
suggest that more likely, the explanation was 
rapid restoration of circulation to ischemic 
myocardium. The functional significance of in- 
creased coronary collateral flow was reflected in 
arrest of anerobic metabolism. Lactate concen- 
tration rapidly diminished. The reduction cor- 
related with marked improvement in cardiac 
function, return to nearly normal hemodyna- 
mics and elevation of arterial oxygen saturation 
suggesting diminished pulmonary congestion. 
Since diastolic augmentation must be carried 
out for a critical period (about thirty minutes 
in the dog) before increased retrograde col- 
