40 
CARDIAC MODELS 
system, both of the occluded portion and of the 
adjacent unoccluded portions and the immedi- 
ate availability of anastomotic collateral flow. 
ACKNOWLEDGEMENTS 
The authors wish to acknowledge the skillful 
technical assistance of Miss Lilo Stucki, Mr. 
Nathaniel Lopey, Mr. Jose Rivera and Mr. Don- 
ald McNiece. The authors also wish to acknowl- 
edge the invaluable secretarial assistance of 
Miss Sally Evans, Mrs. Juliette Newman and 
Miss Margo Nikitas. 
REFERENCES 
1. Salazar, a. E. Experimental myocardial in- 
farction: Induction of coronary thrombosis in the 
intact closed-chest dog. Circ. Res. 9:1351, 1961. 
2. RusHMER, R. F., FiNLAYSON, B. L., and Nash, A. A. 
Shrinkage of the heart in anesthetized, thoraco- 
tomized dogs. Circ. Res. 2:22, 1954. 
3. Frank, M. J., and Levinson, G. E. An index of 
the contractile state of the myocardium in man. J. 
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4. Wegria, R., Segers, M., Keating, R. P., and 
Ward, H. P. Relationship between the reduction in 
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The electrophysiological basis of ventricular ar- 
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7. Waldo, A. L., Kaiser, G. A., Castany, R. J., and 
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ciated with acute myocardial infarction. Suppl. VI 
to Circ. 37/38:200, 1968 (Abstract). 
8. Jorgensen, L., Rowsell, H. C, Hovig, T., and 
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swine. Amer. J. Patho. 51:681, 1967. 
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DISCUSSION 
H. L. Brooks, University of Chicago: My 
question is : In your rather inclusive study, did 
you do any mapping in terms of involvement of 
the septum, the right ventricular free wall and 
the left ventricular free wall in these LAD oc- 
clusions ? 
Dr. Hirsch : Yes we did. I should say that 
we found infarcts. Depending on whether we 
had gone straight down the LAD or off into a 
diagonal branch, if the thrombus was situated 
midway between apex and coronary osteum, we 
would find an infarct that involved the anterior 
wall or that extended around into the anterior 
part of the septum and might have involved also 
the apex as well. Sometimes it wrapped around 
and extended to the diaphragmatic surface of 
the apex. If we went into a diagnonal branch, 
off to the left, we would find an infarct that, 
more typically, involved the anterior wall and 
the free wall of the left ventricle. To make an 
all-inclusive statement: the most distal infarc- 
tion boundary was the underside of the apex. 
The most medial boundary was the ventricular 
septum about half-way from the front to back. 
The most superior portion was where the 
thrombus was and that was never less than 
about 1 or IV2 centimeters below the bifurca- 
tion of the LAD from the circumflex. The 
most lateral involved a good deal of the free 
wall of the left ventricle. 
P. Somani, Abbott Laboratories, North Chi- 
cago : Have you followed these dogs long enough 
to know what happens to the thrombus ? Does it 
dissolve naturally or what is the progress ? How 
long does it take ? 
Dr. Hirsch : Yes the thrombus evolves ; it is 
in fact a quite dynamic structure. In the first 
three to four hours we would see lots of plate- 
lets and some fibrin. Within one to three days 
there would be much less platelet material, 
large amounts of fibrin, and within three to 
seven days you'd see infiltrates with inflamma- 
tory cells right through the thrombus. We 
didn't follow any dogs for more than eight days. 
