ROBERT L. HAMLIN AND C. ROGER SMITH 
617 
K. T. Lee, Albany College of Union Univer- 
sity, Albany, N.Y. : What are the differences in 
electrocardiograms of human and swine? We've 
been doing some swine electrocardiograms and 
I think there are some differences. Do you have 
some experience? 
Dr. Hamlin: Yes, we find that the pig lies 
somewhere between the ruminant and the car- 
nivore. And we place it approximately in the 
IIB category, along with the horse and the dol- 
phin. People have made the analogy that the 
dolphin is akin to a swimming pig. If one looks 
at the axis, (the anterior posterior or dorsao 
ventral axis), one finds that in pigs the mean 
and major forces are directly dorsal, (that is 
to the back) ; as opposed to man, whose forces 
might be 50% anterior and 50% posterior. So I 
think there are rather striking differences in 
swine as compared with man, but swine fit very 
closely with horses and dolphins. The pig may 
be an unfortunate animal in some cases because 
he has this nearly completely penetrating Pur- 
kinje system. If the experiment you're conduct- 
ing depends upon studying the hemodynamic 
consequences of this conduction system, say 
you're forcing the heart with some pathological 
means, that's one thing. But, if it depends upon 
conduction disturbance, then it's quite another, 
because the pig is much less likely to get sig- 
nificant conduction disturbance because of this 
anastomosing Purkinje system. 
E. F. Jankus, University of Minnesota, St. 
Paul : It's a tremendous job to try and classify 
these various conduction routes on a species' 
basis. I wonder if you would comment on 
Davies' report in the 1930's about the Purkinje 
distribution via the coronary arteries. 
Dr. Hamlin: Davies did propose that the 
Purkinje system of birds penetrates from epi- 
cardium to endocardium. I'm certain that it 
does. Whether this produces any significant dif- 
ference between that of the bird and the cow 
is questionable, because in any case, it seems 
to penetrate the entire transmural distance, and 
one can account for the activation process sim- 
ilarly as one does with the cow. That is, it 
doesn't matter (if the ventricular free walls are 
excited with a burst of activity) where that 
activity begins, whether the Purkinje fiber 
penetrates from endocardium to epicardium or 
epicardium to endocardium. This is something 
that we're currently investigating. Dr. Moore 
has looked at it in birds and could reflect better 
on the subject. 
Dr. Buchanan: I was puzzled by your dia- 
grams. Could you clear up the nomenclature of 
anterior-posterior as opposed to dorso-ventral ? 
Dr. Hamlin: The Z axis is the anterior 
posterior or dorsal ventral and the Y axis is 
the cranial caudal or superior inferior. 
Dr. Buchanan : Considering the axes on the 
quadruped animals, they're like the bovine, it 
didn't look like you had much QRS potential. 
Now, what were the spike potentials there? 
Dr. Hamlin: There is some activity. Since 
most of the activity ascends the septum in these 
animals, one is most likely to get greatest volt- 
ages in the anterior posterior axis and very 
small voltages in the cranial caudal axis. 
Dr. Buchanan: I was just wondering which 
way because you didn't seem to have enough po- 
tential. 
Dr. Hamlin : There are very small voltages 
in the cranial caudal axis of these animals. 
W. B. Wead, University of Louisville, Louis- 
ville, Kentucky: I was wondering if you have 
a VCG analysis, comparative analysis, and if 
you have, does it hold up under this type of 
division? What is the best lead system that 
you've come up with? 
Dr. Hamlin: We have done vector cardio- 
graphic analyses, and we use the McFee axial 
system. We have tried the Frank system as 
well, and there's apparently very few differences 
between the McFee axial and the Frank. The 
voltages are a little higher in the McFee than 
in the Frank, and they correlate very closely 
with the unipolar thoracic leads. There are some 
local effects, some proximity effects, that one 
sees with a thoracic lead. 
Dr. Wead: Does the position of the McFee 
leads still matter as much in these animals as 
it does in man as opposed to the Frank lead 
system with which you have little bit more 
leeway. 
Dr. Hamlin : I can't say much about the com- 
parison between man and the quadrupeds. It 
appears to be rather insensitive to position in 
the quadrupeds. 
