106 
CARDIAC MODELS 
A myocardial infarction-like syndrome has 
been induced in "chair"-restrained M. rmdatta 
by isoproterenol given subcutaneously.^" Al- 
though the effective dose was extremely high 
(100 mg/kg), only 2 of 16 monkeys died from 
its administration. The electrocardiogram ob- 
tained under these extreme conditions was simi- 
lar to the one observed in myocardial infarction 
in man: abnormal Q waves, elevated S-T seg- 
ment, and T-wave inversion. However, unlike 
the results in man, the Q waves disappeared 
after 8 to 10 days and the ECG's were practi- 
cally normal after 20 to 30 days. The hemody- 
namic changes, which tended to disappear in a 
few days, included a lowering of the blood pres- 
sure, which, however, remained above shock 
levels, peripheral vasodilation, tachycardia, and 
a moderate early increase in cardiac output 
(dye injection method) . SGOT became elevated 
12 to 24 hours after the injection of isoproter- 
enol and returned to normal 3 to 4 days later. 
Strangely enough the microscopic changes, ex- 
treme nuclear and fibrillar disruption, were ap- 
parently reversible up to 60 days since no gran- 
ulation tissue had replaced the muscular fibers. 
Recently we reported the hemodynamic and 
pathologic changes observed in "chair"-re- 
strained M. mulatta when myocardial infarc- 
tion was induced by the tightening of a snare 
that had been placed around the left anterior 
descending coronary artery a few days pre- 
viously.^'^ This paper as well as some unpublished 
observations^^ are freely quoted here. 
MATERIAL AND METHODS 
Sixty adult male and female Macaca mulatta 
weighing between4.5 and 9.5 kg were studied. 
Nine animals used during the development of 
the technique are not reported here. Twenty mg 
of succinylcholine chloride (Quelicin,'^' Abbott 
Laboratories) were administered intravenously 
and a cuffed endotracheal tube was inserted. 
General anesthesia (0.5 to 1.25% halothane 
(Fluothane, Ayerst Laboratories, Inc.) vapor- 
ized in a Fluotec vaporizer with 40% nitrous 
oxide and 60% oxygen) was administered with 
a Boyle's anesthesia machine. 
A polyvinyl chloride catheter placed in the 
aorta via the femoral artery was connected to a 
transducer (Statham Laboratories, Inc.) to 
monitor blood pressure during surgery and 
again several days later during the ligation ex- 
periment. The pericardium was opened after a 
midline sternotomy, and an electromagnetic 
square wave flow probe (Biotronex Laborato- 
ries) was placed around the aorta just superior 
to the coronary arteries. A polyvinyl catheter 
was placed in the left atrium by means of a 
purse-string suture. A nylon filament snare (8 
lb. test) , loosely placed around the left anterior 
descending coronary artery 2 to 3 mm distal to 
the origin of the circumflex branch, was intro- 
duced into a polyvinyl tube with a flared tip and 
the tube was passed through an intercostal 
space; the flared end was sutured to the peri- 
cardium and the tube was filled with vaseline to 
form an air seal. A slow continuous intravenous 
drip of 5% dextrose in water was maintained 
and, depending upon blood loss, whole blood 
from donor rhesus monkeys was transfused. 
If the blood pressure dropped below normal 
levels mephentermine sulfate (7 mg, Wyamine, 
Wyeth Laboratories, Inc.) was given intrave- 
nously. The pericardium and thorax were closed 
routinely after the implanted probe wires and 
left atrial catheter were brought through the 
chest. After surgery and intramuscular injec- 
tions of penicillin and procaine penicillin G (Bi- 
cillin CR, 1,200,000 units), the monkeys were 
placed in specially designed suits and recuper- 
ated in a cage for 3 to 5 days. 
Series i 
Twelve male and 22 female adult M. mulatta 
were considered suitable for this study, the ex- 
perimental design of which is shown in Figure 
1. On the morning of occlusion, subcutaneous 
wires were sutured to the proximal part of the 
four limbs and to three chest positions (Vi and 
V3 were 1 cm below the right and left mam- 
mary papilla, respectively; V5 was placed 1 cm 
lower than V3 and at the anterior axillary 
line). The animals were placed in restraining 
"chairs" and pressure transducers were located 
at the level of the heart. Four to 6 recordings at 
15-minute intervals were averaged for the con- 
trol values. After an apparent steady state had 
been reached, the snare was gradually tightened 
