150 
CARDIAC MODELS 
2.5 
2.0 
y 1.5 
I- 
< 
01 
UJ 
o 
o 
o 
UJ 
1.0 
0.5 
N 
(ID 
RVH 
(10) 
CHF 
(8) 
N 
(8) 
RVH 
(10) 
RIGHT 
VENTRICLE 
LEFT 
VENTRICLE 
Figure 10. — The average norepinephrine concentration 
of the right and left ventricles of cats in the normal, 
RVH and CHF groups. Vertical lines with cross bars 
= ± 1 SEM. Numbers in parentheses = number of 
animals in each group. (Reproduced with permission 
from the American Heart Association, Inc. from Cir- 
culation Res. 21:341, 1967.) 
likely that there are multiple abnormalities in 
the metabolic processes of the experimentally 
failing heart. At present it can be concluded 
that at least the following two abnormalities 
are present: (1) a depression of the failing 
heart's ability to utilize fatty acid, and (2) a 
depression of myofibrillar ATPase. In addition, 
many workers have postulated that there may 
be a decrease in the release of calcium by the 
sarcoplasmic reticulum. 
Myocardial Norepinephrine Concentration 
and Response 
Marked depression of the cardiac norepi- 
neprine concentrations was observed in both the 
right and left ventricles of the right ventric- 
ular hypertrophy and congestive heart failure 
groups. The extent of depression was compar- 
able in both of these experimental groups 
(Figure 10). The inotropic effect of L-norepi- 
nephrine was studied in the muscles from eight 
normal cats and six cats with pulmonary artery 
constriction. Four of these were in the right 
ventricular hypertrophy group and the other 
two in the congestive heart failure group, but 
because of the small size of these two groups 
and the fact that all six hearts showed severe 
depletion of right ventricular norepinephrine to 
a concentration of 0.39 micrograms/gm. or less 
(norepinephrine concentration in these right 
ventricles averaged 0.18 ± 0.12 micro- 
grams/gm.), they were analyzed as a sin- 
gle group and compared to the normal. All 
muscles responded to norepinephrine with an in- 
crease in tension and the increments were 
greater in muscles from the cats in the right 
ventricular hypertrophy and congestive heart 
failure groups (Figure 11) . For example, at the 
g / mm 
ISOMETRIC 
FORCE 
• Normal 
▲ RVH and CHF 
NE 
Figure 11. — Effects of exogenous norepinephrine on 
isometric tension of papillary muscles of cats in the 
RVH and CHF groups. 1-norepinephrine was added 
to the muscle bath at 5-min. intervals in increasing 
concentrations starting at IQ-^^M, while isometric ten- 
sion achieved at each concentration was recorded at 
Ln,:,x. The increment in isometric tension is shown 
on the ordinate and the concentration of added nore- 
pinephrine (NE) on the abscissa. Solid circles = 
muscles from normal hearts; solid triangles — mus- 
cles from the norepinephrine-depleted hearts of ani- 
mals in the RVH and CHF groups. Vertical lines 
with cross bars = ± 1 SEM. (Reproduced with per- 
mission from the American Heart Association, Inc. 
from Circulation Res. (21:341, 1967.) 
