K. T. LEE, J. JARMOLYCH, D. N. KIM AND W. M. LEE 
101 
11-11-71 
11-15-71 
13.30 
14:00 
cont 
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Figure 11. — Lead II electrocardiograms of a swine fed 
the severe diet and X-irradiated twice show sinus 
rhythm with deep Q wave on 11/11. On 11/15 slow 
nodal rhythm developed and this was followed by ven- 
tricular tachycardia and ventricular fibrillation. 
proximately 4 weeks after the last x-irradia- 
tion. 
The role played by propylthiouracil is not 
clear. It was used because it is known to pro- 
duce much higher serum levels of cholesterol 
than if dietary cholesterol is given without it. It 
has the inherent disadvantage of inducing met- 
abolic changes that can complicate interpreta- 
tion of observations related to the ischemic 
heart disease. However, atherosclerosis of simi- 
lar magnitude with myocardial infarction and 
sudden death was produced in swine fed the 
moderate diet which does not contain propyl- 
thiouracil. Thus it appears that propylthiour- 
acil is not an essential feature of the regimen. 
We have found a remarkable similarity in the 
11-11-71 
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11.10 
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Figure 12. — Lead II electrocardiograms of a swine fed 
the severe diet and X-irradiated twice. On the day of 
sudden death sinus rhythm was observed initially but 
it developed advanced AV block which was followed 
by complete AV block and ventricular asystole. 
effectiveness of the moderate diet and the se- 
vere diet in producing ischemic heart disease 
with its complications. The euthyroid state does 
not appear to protect the swine from the effects 
of the atherogenic regimen. 
The occlusive arterial disease produced in 
these swine has many similarities to and some 
differences from that observed in man. The 
most important feature, from the standpoint of 
the objectives of the study, is that the lumen is 
narrowed and blood flow to parts of the myocar- 
dium is reduced. The swine frequently develop 
ischemic heart disease with myocardial infarc- 
tion, sudden death with cardiac arrhythmia, 
and occasionally congestive heart failure. Thus 
the model would appear to be useful for studies 
aimed at elucidating and preventing physiologi- 
cal derangements resulting from ischemic heart 
disease. 
The lesions involve the major branches of the 
coronary arteries, with severity varying from 
branch to branch as in man. However, the 
marked luminal narrowing extends over longer 
segments than are usually seen in man. Throm- 
bosis, which is common in man, was not seen 
grossly even in those with myocardial infarcts. 
Instead, hemorrhage into plaques was much 
more frequent than in man. 
Histologically all features of the arterial le- 
sions in the swine can be found in man. As in 
man the predominant cell was the smooth mus- 
cle cell, much lipid was present both intra- and 
extracellularly, and regions of necrosis and cal- 
cification could be found. However, the cellular 
component was more prominent and the ne- 
crotic debris and calcification were much less 
prominent than with advanced coronary ather- 
osclerosis in man. This is to be expected in rap- 
idly developing lesions since the early phase in 
both man and experimental animals appears to 
be largely cellular proliferation, with extensive 
fibrosis and large regions of necrotic debris de- 
veloping later. 
There were no significant gross features other 
than pericardial fibrosis that could definitely be 
attributed to x-irradiation per se. The swine 
treated with x-irradiation alone did not develop 
demonstrable gross arterial or myocardial les- 
ions. The action of x-ray was apparently 
through local enhancement of the atherogenic 
