OBSERVATIONS ON EXPERIMENTAL MYOCARDIAL 
INFARCTIONS IN DOGS 
Jacob I. Hirsch, Fritz Streuli and Fred Gorstein* 
During development of a standardized reproducible 
method for producing coronary thrombosis and my- 
ocardial infarction in closed chest, anesthetized dogs, a 
number of accompaniments of the pathologic sequence 
were studied. 
Electrocardiographic pattern changes which accom- 
panied myocardial infarction in the dog were compara- 
ble to those in man. In almost all experiments early 
ventricular arrhythmias appeared about one-half hour 
after infarction, and lasted about 2 hours. Although 
easy to control with intravenous lidocaine, these were 
potentially lethal. After about an hour or two of quies- 
cence, late ventricular arrhythmias appeared, lasting as 
long as 72 hours. These were quite resistant to therapy 
with lidocaine, but have proven to be fairly innocuous. 
Among the serum enzyme changes, CPK elevation 
appeared first accompanying infarction. LDH elevation 
was last to appear. The ratio of peak levels to pre-in- 
farction levels is greatest for CPK and least for LDH. 
Hemodynamic measurements revealed impairment of 
the circulatory state following acute infarction, slightly 
more than in sham operated dogs. The tendency to re- 
turn toward normal was less for infarcted dogs than for 
sham operated ones. LVEDP showed the greatest 
change, and remained abnormal during the healing pe- 
riod. 
At autopsy, infarcts were located in regions predict- 
able from a knowledge of the site of occlusion, but their 
sizes were much less predictable either from coronary 
arteriographic information or from electrocardiogra- 
phic pattern changes. The elevations in serum enzyme 
activities, especially of CPK, were good predictors of 
infarct size. With one exception, myocardial infarction 
and CPK elevation were either present or absent to- 
gether. 
INTRODUCTION 
Numerous methods have been used to occlude 
coronary arteries and to produce myocardial in- 
farction in animals. We have chosen the method 
first described by Salazar.^ This method con- 
sists in passing a low intensity direct current 
betM^een 2 electrodes, one placed on the skin and 
a second in a major branch of a coronary ar- 
tery. This method v^as deemed to be uniquely at- 
' Department of Medicine, New York University School of Medi- 
cine 
tractive because of a number of features which 
it embodies. The first is obviating thoracotomy 
and pericardiotomy, with their attendant influ- 
ences upon hemodynamic, metabolic and elec- 
trocardiographic changes, changes in acute 
phase reactants and a possible effect upon col- 
lateral vasculature.- The second is the assur- 
ance that in vivo thrombosis at the site of inti- 
mal arterial damage is the means by which the 
artery is occluded. The third is the gradual oc- 
clusion of the artery which occurs, and which is 
controllable to some extent. 
This method of producing coronary occlusion 
by thrombosis and myocardial infarction ap- 
peared highly attractive in comparison to other 
methods. Early reports, however, contain no 
definite information concerning the reproduci- 
bility of the coronary lesion, myocardial infarc- 
tion, and the changes or predictability of the 
electrophysiologic, hemodynamic and metabolic 
responses. In these experiments, we attempted 
first, to modify the experimental intervention in 
ways which would reveal the optimal conditions 
for producing arterial damage, thrombosis, and 
myocardial infarction, and, second, to evaluate 
the results of this experimental intervention. 
The changes produced could then be evaluated 
with regard to their reproducibility, predict- 
ability, quantitation and correlation with the ex- 
perimental intervention. Occlusions were at- 
tempted a 91 sites in the coronary arteries of 
80 dogs. In 5 of these dogs occlusion was at- 
tempted at 2 sites and in 3 of these dogs occlusion 
was attempted at 3 sites. 
METHODS 
Eighty mongrel dogs were used, of which 33 
were females, and 47 males. Their weights 
ranged between 26 and 70 pounds. The dogs 
were lightly anesthetized, using pentobarbital 
anesthesia, or pentobarbital plus morphine sul- 
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