EXPERIMENTAL MYOCARDIAL INFARCTION 
IN NONHUMAN PRIMATES 
M. R. Malinow, J. D. Hill, M, Lees, W. P. McNulty and A. J. Ochsner, III' 
Myocardial infarction was attempted in 60 "chair"- 
restrained, nonanesthetized Macaca mulatta by the 
tightening of a snare previously placed around the left 
anterior descending coronary artery. Aortic flow, ECG, 
arterial and left atrial pressures were monitored. Post- 
mortem examinations showed extensive anterolateral 
septal infarction in animals surviving more than 12 
hours. In 26 monkeys, a discriminant analysis, based on 
hemodynamic data obtained within 30 minutes after in- 
farction, resulted in a retrospective prediction that was 
accurate in all animals dying from cardiogenic shock 
and in 93% of the surviving animals. In 13 monkeys, 
nuclide-labeled microspheres (Scandium-46, Strontium- 
85 and Iodine-125) were injected through a catheter 
into the left atrium; organ blood flows were deter- 
mined before and 15 and 45 minutes after ligation of 
the coronary artery. The results demonstrated a reduc- 
tion of blood flow to all tissues, but the differences were 
not significant in the liver and the adrenals. A redistri- 
bution of the decreased cardiac output favored the 
brain, heart, liver and adrenals where the reduction was 
less than in the rest of the body. 
INTRODUCTION** 
Although atherosclerosis occurs frequently 
among monkeys, myocardial infarction is ex- 
tremely rare. The latter has been reported in 
single cases of Lemur macaco,^ Cercocebus 
collaris,^ and Hylobates concolor^ by Hamer- 
ton, and in single cases of chimpanzees reported 
separately by Manning,*' Burlingame,'' and 
RatclifFe ;^ RatclifFe also described a transmural 
infarction in a Gorilla gorilla.^ Myocardial in- 
farction was observed by Taylor et al.^° in one 
of the 15 rhesus monkeys fed a high fat-high 
cholesterol diet for 40 months and by Andrus et 
al. in 3 of 14 chimpanzees that had received a 
high fat-high cholesterol diet for 12 months.^^ 
Hemodynamic or electrocardiographic studies 
* Oregon Regional Primate Research Center, Beaverton, Oregon 
and University of Oregon Medical School, Portland, Oregon 
** Supported by Contract PH-43-68-686/The Artificial Heart-Myo- 
cardial Infarction Program of the National Heart and Lung Institute 
and Grants FR 00163 and HE 12594 frum the National Institutes of 
Health. 
have not been reported in any of these animals. 
The coronary arteries of monkeys were li- 
gated by earlier investigators,^^'^^ and in 
some cases the ensuing myocardial infarction 
was studied. Extensive research in this field has 
been conducted by deWaart et al.,^* who ligated 
either the anterior descending or the right coro- 
nary artery in 31 crab-eating macaques (M. 
irus) ; in one of these animals, both coronaries 
were ligated. Three-lead electrocardiograms 
were obtained and some of the animals were 
followed up to 6 months. Although, in general, 
the earliest changes could not be documented 
because records were obtained after the chest 
had been closed, the tracings were well corre- 
lated with the location of the infarction, and the 
electrocardiographic evolution was carefully 
studied. Myocardial infarction has also been in- 
duced in nonrestrained M. mulatta by radio con- 
trol of a snare placed around the left anterior 
descending coronary artery and brought 
through the anterior chest by means of a polyvi- 
nyl tubing. 1^ After the animals had recuper- 
ated (generally a week), the snare was secured 
to the capstan of a motor with an attached bat- 
tery-operated electronic switch. Electrocar- 
diographic leads (CFi) were sutured and 
connected to a miniaturized amplifier and trans- 
mitter. When the animals had been returned to 
their cages, the motor was remotely activated 
with a transmitter and the coronary snare was 
thereby tightened. The ECG was monitored on 
an oscilloscope and recorded at appropriate in- 
tervals. Tightening of the snare was stopped 
when signs of electrical injury appeared. One of 
the 6 monkeys died of ventricular fibrillation; 
the rest were sacrificed 3 to 4 weeks after occlu- 
sion. The electrocardiographic pattern was sim- 
ilar to that in human cases of anterior wall in- 
farction, and necrosis of the myocardium was 
found in the postmortem studies. 
105 
