CARDIAC EFFECTS OF HEMORRHAGIC SHOCK IN DOGS AND 
OTHER ANIMALS 
D. B. Hackel, J. Chang, N. B. Ratliff and E. Mikat* 
The dog has been used extensively in studies of the 
effects of hemorrhagic shock. The present report will 
describe the changes seen in the myocardium of dogs 
and other animals subjected to oligemic hypotension. 
These include two types of lesions: 1) subendocardial 
hemorrhage and necrosis, which are predominantly the 
result of hypoxia; and 2) "zonal" lesions, which ap- 
parently result from hemodynamic factors inherent in 
the shock state. The formation of both lesions is aug- 
mented by increased sympathetic activity and is de- 
creased or prevented by blocking catecholamine effects. 
Zonal lesions are found in cats and pigs subjected to 
shock, and in a lesser severity in rabbits and humans, 
but not in rhesus or squirrel monkeys. Subendocardial 
hemorrhage and necrosis occur in all animals studied 
except rabbits. 
INTRODUCTION** 
Studies of the pathological effects of experi- 
mental hemorrhagic shock have concentrated on 
the dog, but numerous descriptions also exist of 
observations in various animals ^ such as cats, 
rats, rabbits, monkeys, and goats, as well as in 
man.2 It is well recognized that shock involves 
most organs of the body in all animals that have 
been studied and, at the same time, it is known 
that the intensity of involvement of some or- 
gans varies between different species. For ex- 
ample, the splanchnic congestion seen promi- 
nently in dogs^ is only a minor feature of the 
shock syndrome in primates.^'^ Thus, it is of 
potential importance to know the comparative 
pathological effects of shock in different animal 
species. 
DISCUSSION 
There has been evidence from numerous phys- 
iologic studies of the important contribution 
♦Department of Pathology, Duke University Medical Center, 
Durham, North Carolina. 
♦♦Supported by U.S.P.H.S. grant HL-05875 and carried out dur- 
ing the tenure of a Career Research Award from the USPHS (HL- 
K6-14,188). 
of cardiac failure to "irreversibility" of experi- 
mental shock.'' We have studied the character 
of the anatomic changes that are induced in the 
hearts of animals subjected to hemorrhagic 
shock, and have demonstrated two types of le- 
sions that are different in appearance and in 
etiology: 1) subendocardial hemorrhage and 
necrosis, and 2) "zonal" lesions. 
Subendocardial hemorrhage and necrosis of 
the myocardium are commonly seen in shock, 
but are not specific for the shock syndrome. 
They have been frequently recognized as occur- 
ring secondary to situations in which the com- 
mon elements of increased sympathetic activity 
and hypoxia are present.'^ We have demon- 
strated that these lesions can be prevented by 
blocking beta sympathetic activity,^ by prevent- 
ing the usual tachycardia that occurs in shock ^ 
or by treating the animals with an increased 
concentration of oxygen at hyperbaric levels.^" 
The second type of myocardial damage that 
occurs in shocked animals has been referred to 
as "zonal" lesions."-^^ They seem to occur only 
in a setting of oligemic hypotension, and thus 
are rather specific for shock. The lesions can be 
seen in routine light microscopic sections, but 
are obscure and difficult to differentiate from 
artifacts and contraction bands. However, 
frozen sections stained for oxidative enzyme 
activity (such as succinic dehydrogenase) re- 
veal their unique characteristics.^^ They are 
recognized in the papillary muscles of both 
ventricles, and in the subendocardial regions 
mainly of the left ventricle as slightly swollen 
ends of myocytes that have a clear zone ad- 
jacent to the intercalated discs, with a margin 
of increased enzyme activity. See Figure 1. 
This appearance is confirmed by electron micro- 
scopic study as representing a focal hypercon- 
traction of the ends of some myocytes, with 
scalloping of the sarcolemma, bizarre bending 
813 
