100 
CARDIAC MODELS 
29 swine died suddenly. All had advanced 
coronary atherosclerosis and 25 had myocardial 
infarcts. Most of them were found dead in 
cages, but five died suddenly soon after experi- 
mental procedures, such as coronary angio- 
gram, electrocardiogram or while preparing for 
anesthesia. In seven swine, it was possible to 
obtain terminal electrocardiograms. Five 
showed ventricular fibrillation and two showed 
ventricular asystole. 
Another group of 40 swine were fed the se- 
vere (TSC) diet. Dietary regimen and method 
of x-irradiation were similar to those in the Se- 
ries I study. The amount of calories given per 
day was 2,500. Serum cholesterol levels reached 
500-1,300 mg% within two months on the se- 
vere diet. After 9 weeks on the diet, two doses 
of x-irradiation were given with 4 week inter- 
vals. This group was set up to serve as a control 
group for the moderate diet group as regards to 
the degree of coronary atherosclerosis and the 
incidence of myocardial infarction. Thirty-two 
swine were x-irradiated twice. Starting from 3 
weeks after the second x-ray 28 swine died sud- 
denly. All had severe coronary atherosclerosis 
and 26 had myocardial infarcts. The majority 
of them died suddenly in cages without appar- 
ent prodromal syndrome, and eleven died sud- 
denly after various experimental procedures as 
was the case in the moderate diet group. In nine 
swine terminal electrocardiograms were taken. 
Six showed ventricular fibrillation and three 
showed ventricular asystole. 
Coronary angiograms were taken in the ma- 
jority of the swine in Series II. Varying degrees 
of luminal narrowing of coronary arteries were 
demonstrated. Although they were consider- 
able individual variations, in general the swine 
fed the severe diet appear to have more marked 
narrowing of the lumen than those fed the mod- 
erate diet. 
Four sets of ECG telemetry systems were 
used to monitor electrocardiograms of selected 
swine fed either the severe or moderate diet. In 
one severe diet-fed swine multiple premature 
ventricular contractions were detected for 2 
days by the telemetry system approximately 6 
days before death. This swine died rather sud- 
denly, and ventricular fibrillation was detected in 
the terminal electrocardiogram (Figure 10). 
Terminal electrocardiograms were obtained 
in 16 swine with sudden death syndrome, of 
which 9 had been fed the severe diet and 7 had 
been fed the moderate diet. In 10 swine, ter- 
minal ventricular fibrillation was usually pre- 
ceded by complete AV block, slow idioventricu- 
lar rhythm or runs of ventricular tachycardia 
(Figure 11). In six swine, the terminal event 
was ventricular asystole following complete AV 
block and extremely slow idioventricular 
rhythm (Figure 12). 
COMMENTS 
As presented above, advanced occlusive coro- 
nary artery disease with myocardial infarction 
and sudden death can be induced rapidly in 
swine by using a combination of injurious and 
atherogenic agents. The most elTective combina- 
tion, to date, is given in the following sequence : 
(1) young miniature swine are given a high- 
fat, high-cholesterol diet with or without pro- 
pylthiouracil ; (2) x-irradiation of the precor- 
dium (1,500 r) is given after 8 weeks or more 
on the diet; (3) a second x-irradiation is given 
4 to 5 weeks later. Severe coronary artery dis- 
ease and its complications begin to appear ap- 
TSC 306 
8-24-71 
900 
12:00 
14:00 
6-25-71 
6-30-71 
1 
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• I 
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1 
1 . ; 
1 1'! 
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I 
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■■A 
Figure 10. — Lead II electrocardiograms of a swine fed 
the severe diet and X-irradiated twice show increasing 
number of ventricular premature beats with frequent 
brief runs of ventricular tachycardia (6/24-6/25) 
and final ventricular fibrillation (6/30). 
