48 
CARDIAC MODELS 
ECG 
(Lead E) 
Baseline 
600 mmHg 
800 mmHg 
1000 mmHg 
200 
HEART 
RATE 100 
(beats/min) 
-V- 
AORTIC 
PRESSURE 
(mm Hg) 
150 
100 
50 
0 
LV 
PRESSURE 
(mm Hg) 
L V 
PRESSURE 20)- 
( mm Hg) 
\ 
V 
CIRCUMFLEX leoop 
BALLOON 
PRESSURE 
( mm Hg ) 
800 ^ 
J 
2 min 
Figure 10. — -Stable left ventricular failure produced by total occlusion of the left anterior descending plus graded 
constriction of the circumflex coronary artery in a dog. Control of the degree of circumflex constriction was 
achieved by monitoring and holding constant the pressure in the implanted circumflex balloon. Increasing 
severity of left ventricular failure is evident from the rise in heart rate and left ventricular end-diastolic 
pressure as circumflex balloon pressure is successively increased to 600, 800, and 1000 mm Hg. (By permis- 
sion.'=) 
cate that marked left ventricular decompensa- 
tion does occur.^^ 
OBSERVATIONS ON THE OCCURRENCE OF 
PAIN REACTIONS IN ANIMAL STUDIES OF 
MYOCARDIAL ISCHEMIA 
Studies of acute myocardial infarction in 
dogs, pigs and calves are notable for the lack of 
any apparent pain reaction or discomfort on the 
part of the animal. Dogs sometimes appear to 
become slightly restless several minutes after 
total and permanent coronary occlusion, but 
this is variable, and is not influenced by the 
presence or absence of morphine pre- 
treatment.i* Whether this lack of pain reaction 
represents a species difference from man, the 
effect of sedation, the effect of vessel dissection 
and interruption of nerve supply to the heart 
during placement of the coronary balloon oc- 
cluding cuff, or some other yet undiscovered 
cause remains unknown. It may be appropriate 
to study a species more closely related to man, 
in M^hich it might be possible to condition ani- 
mals to give an indication whether pain is pres- 
ent or absent. We have recently initiated stud- 
ies in baboons with implanted coronary artery 
balloon occlusion cuffs.-* Testing in one animal 
showed that typical electrocardiographic coro- 
nary ischemic patterns are obtained (Figure 
11). Thus far, only transient one-minute occlu- 
Control Occlusion (Imin) 
(L. Chest Lead) ^ '^'^\r\'--Y-Y-^ic'^~\^-V'^^ 
I Sec 
Figure 11. — Left: Resting electrocardiogram obtained 
in an unanesthetized baboon. Right: Tracing ob- 
tained one minute after left anterior descending coro- 
nary artery occlusion, showing marked elevation of 
ST segments. 
