158 CARDIAC MODELS 
PiGURK 1. — ^The double catheter system and the helical coil wire that fits snugly over the inner catheter. Release 
of the wire is achieved by forward thrust of the outer catheter against the coil. 
#7752) was previously shaped with 45° curves 
at 2.5 cm and 0.9 cm from the tip. The first 
curve braces against the aortic wall and stabi- 
lizes the tip. The smaller catheter (P.E. 90) is 
then advanced while slowly rotating the outer 
catheter until the left coronary ostia is identi- 
fied. The inner catheter is then further ad- 
vanced down the main left coronary branch and 
its position verified by injection of contrast 
media. The helical coil wire placed over the 
inner catheter is released by forward pressure 
of the outer catheter. The helical coil consists of 
a magnesium alloy wire 0.02" diameter, which 
is formed into a spring-type coil by winding 
around a 18-20 gauge needle to form a coil ap- 
proximately one-half centimeter long. At least 
four complete turns of the coil within the 0.5 cm 
length are necessary for the intravascular clot- 
ting process to develop. The coil floats freely 
down the selected coronary artery branch and 
lodges into position but permits blood flow 
through its lumen. Gradual occlusion occurs by 
clotting over the next 12 to 36 hours. The outer 
preformed catheter can be left in the aorta for 
recording of blood pressure, withdrawal of sam- 
ples, and recatheterization of the coronary ar- 
tery. 
Serial ECG's, aortic mean blood pressure, 
and cardiac output by the dye dilution technique 
(Cardiogreen, Gilford Model No. 103 IR densi- 
