62 
CARDIAC MODELS 
studies we have undertaken by utilizing this 
shock model. 
TECHNIQUE 
In order that control studies may be per- 
formed in the awake sedated animals, a double 
catheter was designed with a smaller catheter 
inside a larger one.^ The smaller inner catheter 
can be left in the circumflex coronary artery 
without interfering with coronary blood flow 
until the time of injection of the mercury. This 
catheter has been described previously by us 
and was also used for the wire technique to pro- 
duce localized thrombotic occlusion of a large 
coronary artery which will be described in de- 
tail in this meeting by Dr. Stanley. The large 
outer catheter is preformed with two curves : 
the one about 9 mm from the tip, the other a 
mild curve 25 mm from the tip giving an overall 
45° curve of the entire catheter (Figure 1). 
The catheter leans with its second curve, 
against the wall of the aorta, while the tip is di- 
rected toward the left main coronary artery. 
The small inner catheter, which is a PE 90 poly- 
ethylene catheter, is then advanced through the 
outer catheter into the left coronary artery and 
directed to the circumflex branch. The position 
is verified under image intensifier with small 
amounts of dye injections. (Figure 2 a and b) 
The inner catheter can then be left in place 
until the time of mercury injection without 
interfering with the coronary blood flow. The 
outer catheter is slightly withdrawn to avoid 
blocking of the ostium of the left coronary ar- 
tery. 
Initially the animals are anesthetized with in- 
travenous sodium thyopenthal (10 mg/kg) and 
cutdowns are made using xylocaine to inflltrate 
the skin. The coronary catheter is introduced 
l""ll"''l"ll"Hi")!liinllliiliililfi.,lm:ii.,l.n;innli^ 
Figure 1. — Double catheter assembly for selective catheterization of coronary arteries in dogs. 
