STUDIES OF A CARDIOGENIC SHOCK MODEL 
p. Kezdi, S. N. Misra, R. K. Kordenat and T. J. Smith* 
Selective embolization of the circumflex branch of 
the left coronary artery in the dog with minute amounts 
of metallic mercury resulted in predictable cardiogenic 
shock and pump failure and enabled us to study the 
natural history, the effect of drug interventions, and 
calculations of myocardial energetics in this condition. 
Decrease of left ventricular dP/dt and cardiac output 
were the two most reliable hemodynamic parameters in 
predicting irreversible shock and early death. Continu- 
ous decline of these parameters below 50% of control 
after the first hour of shock was a bad prognostic sign. 
These findings corresponded with clinical observations 
of others that the fundamental pathophysiologic change 
in shock is depressed myocardial contractility. In addi- 
tion, end-diastolic and end-systolic volumes, determined 
by dye dilution technique, showed significant increase 
along with a significant decrease in ejection fraction 
during the shock state. The calculation of energetics of 
the heart, including wall force and tension along with 
fiber shortening and contractile element work, corre- 
sponded with the above findings. In a group of experi- 
ments, the effect of drug interventions was studied 
when hemodynamic deterioration reached the irreversi- 
ble shock state. Alpha and beta adrenergic blockade 
and stimulation alone and in combination were studied. 
Significant hemodynamic improvement, along with im- 
provement of kidney and other vital functions, was ob- 
served with combined use of carefully titrated minute 
doses of norepinephrine and isoproterenol. The dose 
range tested was that commonly used clinically. The 
value of combined use of the above drug treatment in 
human myocardial infarction with shock was confirmed 
in five patients who showed marked improvement. This 
is a predictable and reproducible experimental model of 
shock and pump failure which provided further insight 
into underlying physiological derangements and helped 
to delineate the best pharmacologic intervention. The 
experience in the experimental laboratory could be di- 
rectly extrapolated to the clinical state. 
INTRODUCTION** 
The great increase of myocardial infarction 
generated much interest for the development of 
animal models which simulate human my- 
* Cox Heart Institute, Kettering Medical Center, Dayton, Ohio. 
** This work was supported by NIH Grant HE-09885 and in part 
by Contract PH-43-68-688. 
ocardial infarction. Models have been designed 
for the study of hemodynamic mechanisms dur- 
ing the development and course of myocardial 
infarction and for the study of its complications 
such as arrhythmias and cardiogenic shock. We 
have been interested in suitable models of my- 
ocardial infarction resulting from occlusion of a 
large coronary artery and of myocardial infarc- 
tion with cardiogenic shock by some other tech- 
nique since shock usually does not develop with 
the acute occlusion of a large coronary artery in 
animals. A model of myocardial infarction with 
shock will closely simulate the human condition 
only if : 
1. It can be produced in a closed chest ani- 
mal ; 
2. Observations can be made in the unanesth- 
etized, unrestrained state ; and 
3. Natural history and mortality can contin- 
ually be observed. 
The multiple techniques proposed usually do 
not fulfill all of these criteria. It appeared to 
us that the best suited technique for this pur- 
pose is the one originally reported by Lluch et 
al."* who used selective injection of metallic 
mercury into the coronary arteries. While this 
technique does not result in narrowing or ob- 
struction of a major coronary artery, its end re- 
sult on the affected myocardium is very similar 
in that it leads to localized hypoxia, functional 
impairment and necrosis of the myocardium, 
and a clinical picture very similar to human 
cardiogenic shock. We have therefore adapted 
this technique for our studies and slightly modi- 
fied it, predominantly by applying a special 
catheter developed in our laboratory, which al- 
lows selective embolization of any of the 
branches or the main branch of the circumflex 
coronary artery. This report describes the tech- 
nique, the hemodynamic results and the various 
61 
