144 
CARDIAC MODELS 
1 
1 
descending aorta via the femoral artery, the 
electrocardiogram is monitored and a number 
five French birdseye catheter is placed in the 
body of the right ventricle via the right exter- 
nal jugular vein. Right ventricular and aortic 
pressures are measured by Statham force trans- 
ducers (P23Db) and all signals are recorded on 
a multichannel Sanborn oscillograph. The zero 
reference point is taken as the midchest posi- 
tion, corresponding to the level of the right 
atrium. Cardiac output is determined by the dye 
dilution technique with the injection of 1.25 mg. 
indocyanine green (1 cc.) into the right ventri- 
cle and sampling from the abdomonial aorta. 
Mixed venous and arterial blood samples were 
obtained from the right ventricle and aorta, re- 
spectively, and analyzed for oxygen content by 
the Van Slyke technique. 
RESULTS 
Hypertrophy and Failure 
By using this method, the pulmonary artery 
can be constricted to an average residual lumen 
of 10% of normal by the 2.8 mm. clips and to 
20% of normal by 3.5 mm. clips. Pulmonary 
banding by either clip produces right ventricu- 
lar systolic hypertension and results in right 
ventricular hypertrophy. The increment in- 
crease in weight of the right ventricular free 
wall was 80% of the control weight or greater 
in every animal from either group studied one 
week or longer after constriction of the pulmon- 
ary artery. Following constriction with 2.8 mm. 
clips overt congestive heart failure was present 
in addition to right ventricular hypertrophy in 
80 % of the cats sacrificed an average of 26 days 
after operation. Criteria used to denote overt 
congestive heart failure included pleural fluid, 
hepatic congestion, ascites, elevation of right 
ventricular end-diastolic pressure (Figure 2) 
reduction of cardiac index and an increase in 
the arteriovenous oxygen diff'erence. Gross 
pleural and/or ascitic fluid were present in 75% 
of the animals with heart failure; in 75% of 
these animals, two or more of the criteria of 
failure were present. The cats with the 2.8 mm. 
clips also had marked dilatation of the right 
ventricular chamber and some demonstrated 
right ventricular pulsus alternans. Sixty per- 
cent of the animals with 2.8 mm. clips died with 
evidence of severe congestive heart failure be- i 
fore catheterization or sacrifice for study. 
Right ventricular weight increased promptly 
after the constricting operation and then rose 
less rapidly (Figure 3). The right ventricular 
weight in normal cats averaged 0.55 ± 0.02 
(S. E. M.) gms./kgm. body weight. These 
weights were significantly increased above nor- 
mal one or two days after constriction, averaging 
0.7 ±: 0.04 and 0.9 ± 0.05 kilograms, re- 
spectively. In cats in which right ventricular 
hypertrophy alone was produced by constriction 
of the pulmonary artery to 20 % of its original 
lumen with a 3.5 mm. internal diameter clip, 
the right ventricular weight averaged 1.05 ± 
0.6 gms. kgm. In animals in which congestive 
heart failure, as well as right ventricular hyper- 
trophy was produced by constriction of the pul- 
monary artery to 10% of its original lumen by 
a 2.8 mm. clip, the right ventricular weight av- 
eraged 1.33 it 0.10 gms./kgms. Similar results 
were observed in the left ventricle of guinea 
pigs after constriction of the ascending aorta.^^ 
The very rapid onset of significant ventricu- 
lar hypertrophy after an abnormal load was im- 
posed on the heart is of interest and somewhat 
100 
RV SYSTOLIC PRESSURE 
RV END DIASTOLIC VOLUME 
mm. 
Hg 
RV WEIGHT 
□ 
NORMAL 
(10) 
RVH 
(5) 
■ 
CHF 
(5) 
Figure 2. — Right ventricular (RV) systolic pressure, 
right ventricular end-diastolic pressure (RVEDP) 
and right ventricular weight from normal, hypertro- 
phied and failing cats. 
