Download Print - Circulation Research

830
Functional Morphology of the Pressure- and the
Volume-Hypertrophied Rat Heart
H U N - L I N LIN, KAZIMIERAS V. KATELE, AND ARTHUR F. GRIMM
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
SUMMARY We studied hearts in which hypertrophy was caused by both pressure and volume overload. Pressure
hypertrophy was induced by an aortic constriction; volume hypertrophy was induced by an iron-copper deficiency
(anemia). The ventricular weight was increased by 34% in the pressure-hypertrophied hearts at the end of 6 weeks.
The ventricular weight was increased by 54% in the volume-hypertrophied hearts at the end of 3 months. A
potassium arrest-formalin fixation technique was used to produce a "diastole-like" ventricle. In the pressurehypertrophied ventricle, the ventricular wall thickness and external radii were significantly increased, whereas the
valve-to-apex distance and internal radii remained unchanged. We also found that in the volume-hypertrophied ventricle there was an increase in the valve-to-apex distance, external radii, internal radii, and wall thickness. Although
external and internal dimensions increased, the ventricular shape did not change significantly in the volume-hypertrophied ventricle.
IN RESPONSE to elevated work loads, the heart may
increase its size and shape. Since a changed geometry of
the heart might be associated with a changed functional
performance, the ventricular shape, lumen size, and wall
thickness have to be considered. The relationships among
these factors are described in the modified law of Laplace,
T = PR/2S, where T is the stress on the wall, P is the
transmural pressure, R is the radius of the lumen, and S
is the wall thickness.
Some investigators1-2 have attempted to apply the Laplace relationship to the functional morphology of the
heart. Several studies :t~" discuss the relationships of
cardiac geometry and functional performance in both
normally growing and hypertrophied hearts. There has
been difficulty in choosing an acceptable physiological
reference for these comparative anatomical studies. On
the basis of cineradiography of radio-opaque metal
markers placed in the left ventricular papillary muscle of
canine hearts, Grimm et al.a concluded that K+ arrestformalin fixation in situ produced a "diastole-like" ventricle.
In the present study, morphological changes were studied in two models of hypertrophy; pressure hypertrophy
(aortic constriction) and volume hypertrophy (induced by
anemia). The K+ arrest-formalin fixation technique was
used to establish a reference position at which the ventricular volumes, shapes, radii, and wall thicknesses were
examined.
From the Departments of Histology and of Physiology, Colleges of
Dentistry and of Medicine, University of Illinois at the Medical Center.
Chicago, Illinois.
This study was partially supported by Grant A76-33 from the Chicago
Heart Association and Grant RR5309-14 from the U.S. Public Health
Service.
This work includes material from a thesis entitled "A Physiological.
Histological and Biochemical Study of the Pressure and Volume Hypertrophied Rat Heart" submitted by Dr. Lin in partial fulfillment of the
requirements for the Ph.D. degree in the Graduate College of the
University of Illinois at the Medical Center, Chicago, Illinois.
Address for reprints: Hun-Lin Lin, Ph.D., Department of Physiology.
National College, Lombard, Illinois 60148.
Received April 26. 1976; accepted for publication May 27, 1977.
Methods
Sprague-Dawley male albino rats were used.
PREPARATION OF ANIMALS
Volume Hypertrophy
Volume hypertrophy was induced by the method of
Korecky and French9. Young rats were made anemic by
an iron-free diet (milk powder). Initial body weights
ranged from 50 to 60 g (20 days after weaning). These
rats were subdivided into three groups.
Experimental Group. These rats were fed iron- and
copper-free milk powder and distilled water.
Control Group. These rats were fed the same iron- and
copper-free milk powder plus a supplemental solution of
ferrous sulfate (1 mg/liter) and cuprous sulfate (0.1 mg/
liter) as their water source.
Normal Group. These rats were fed regular rat chow
and tap water.
The rats were studied after 3 months of this dietary
regime. To confirm that the rats were anemic, the hematocrit was measured in most cases. Blood was withdrawn
from the right renal vein into a heparinized capillary tube
for centrifugation. After 15 minutes at 2500 rpm, the
hematocrit was read from a hematocrit scale.
Pressure Hypertrophy
Pressure hypertrophy was induced by a subdiaphragmatic aortic constriction according to the method of
Grimm et al.10 Initial body weights ranged from 200 to
250 g. The rats were subdivided into three groups.
Experimental Group. The abdominal aorta was constricted below the diaphragm and above the kidneys with
a size 0 silk ligature. The degree of constriction was
predetermined by placing a thin metal rod next to the
aorta and tying the ligature tightly around both rod and
aorta until the aorta was completely occluded. The 1.1
mm diameter rod then was withdrawn. This diameter,
which was now presumably the diameter of the aorta,
MORPHOLOGY OF HYPERTROPH1ED RAT HEART/L/n el al.
induces hypertrophy. Under these conditions, the radius
of the aorta was reduced to about one-fourth normal. In
several of the rats, the blood pressure was measured from
both the left carotid artery and the abdominal aorta
below the ligature.
Sham-Operated Control Group. These rats were subjected to the same surgical procedure, but the ligature
was tied loosely around the aorta.
Normal Group. These rats were not subjected to any
surgical procedure.
All three groups were maintained under identical conditions for 6 weeks.
EXPERIMENTAL STUDIES
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
Rats were anesthetized with sodium pentobarbital (50
mg/kg) and the abdominal aorta was cannulated distal to
the renal intraperitoneal arteries. A polyethylene cannula
was advanced into the thoracic aorta and approximately
4-5 ml of heparinized isotonic saline (9.0 g NaCl, 5000
units heparin/liter) were injected slowly. Subsequently, 5
ml of a heparinized isotonic KC1 solution (11.5 g KC1,
5000 units heparin/liter) were injected quickly into the
aorta via the cannula and produced immediate cardiac
arrest.
After cardiac arrest, the KC1 solution, at a pressure of
100 mm Hg, was perfused through the aorta for 2 minutes.
Subsequently, 10% formalin was perfused through the
aorta for 2 hours at a pressure of 100 mm Hg. The
inferior vena cava was transected distal to the renal veins
0.5-1.0 minute after the start of the formalin perfusion.
This permitted a continuous flow of the fixative through
the vascular system and prevented extensive tissue distension. Approximately 500 ml of 10% formalin was perfused through each rat during the 2 hours of fixation. It
must be emphasized that all the above procedures were
carried out with the chest closed.
In previous studies in which intraventricular pressure
was measured concurrently during these procedures, there
was no evidence of aortic insufficiency.
The well-fixed hearts were removed and the atria carefully trimmed away. The paired ventricles were postfixed
in 10% formalin for an additional 30 minutes and then
placed in distilled water for 30 minutes to remove excess
formalin.
The fixed ventricles were infiltrated with progressively
increasing concentrations of gelatin solutions at 47°C.
The hearts were kept in a 2% gelatin solution for 24
hours, a 5% solution for 48 hours, and a 10% solution
for a minimum of 72 hours. A minute quantity of thymol
was added to the gelatin solutions to serve as a fungicide.
This gelatin infiltration technique was used to minimize
the distortions produced by dehydration which occurs in
many histological embedding methods. Transverse sections fifty fim thick were cut using an American Optical
Spencer sliding microtome. The sections were mounted
on a glass side with glycerin-gelatin. These techniques
have been described."
Photographs (35-mm Kodak Panatomic X film) were
taken of each section using a Leitz photostat. Eight- to
831
10-fold enlargements were printed on Kodak F-4 high
contrast print paper. A steel millimeter ruler was placed
next to the section so that the precise magnification could
be calculated.
The right and left ventricular luminal areas were measured from each print with a K & E 620022 compensating
polar planimeter. The papillary' muscles or trabeculae
carneae were excluded in the determination of the ventricular lumen. In order to test the reliability of this method,
five prints were developed under the same magnification
and were measured by means of this polar planimeter.
The coefficient of variation (sD/mean) of the repeated
measurements of the area was 0.3%. This value includes
the errors in the developing and processing procedures,
individual judgment in the measurements and the accuracy
of the readings from the planimeter. This value established
an acceptable level of reliability for this technique.
The mean left ventricular internal or luminal radius per
section was derived from the cross-sectional areas by
making the Amplifying assumption that the left ventricular
lumen is circular and solving the standard equation: A =
7rr2, for r, where A is the cross-sectional area measured
by the planimeter. The left ventricular free wall thickness
was calculated for each section as the difference between
the derived mean left ventricular internal or luminal
radius and the directly measured left ventricular external
radius.
Values are given as means ± SD. A one-way analysis of
variance (Anova)12 was used to compare the differences
for the same parameter among and between the groups.
Results
VOLUME HYPERTROPHY
As seen in Table 1, the ventricular weight in the
volume-hypertrophied group was significantly increased
in comparison to the control and normal groups. There
were significant increases in the mean right ventricular
volumes and the mean left ventricular volumes in the
volume-hypertrophied group. The valve-to-apex distance
also was significantly increased in the volume-hypertrophied hearts.
The interanl radii, external radii, and wall thicknesses
are presented in Table 1 and Figure 1. The data show
that, at the 80%, 60%, and 40% levels of the valve-toapex distance, these parameters were significantly increased in the volume-hypertrophied hearts with respect
to the control and the normal groups of hearts. The mean
external radius of the hypertrophied hearts at the 60%
valve-apex level was 6.13 ± 0.28 mm. In the control and
normal hearts, the mean radii were 5.07 ± 0.32 and 5.21
±0.11 mm, respectively. The latter two groups were not
statistically different, when corrections were made for the
absolute differences in the size of the rats (see Table 2).
The external radius in the hypertrophied hearts was
statistically greater. The mean internal radius in the
volume-hypertrophied left ventricle at the 60% valveapex distance was 3.42 ± 0.11 mm, whereas it was 2.95
± 0.36 mm in the control group and 2.69 ± 0.16 mm in
CIRCULATION RESEARCH
832
VOL. 41, No. 6, DECEMBER
1977
TABLE 1 Ventricular Dimensions in the Volume-Hypertrophied, Control, and Normal
Groups of Rats
Volume hypertrophy
Body weight (g)
Ventricular weight (mg)
Calculated ventricular weight
( m g)
Right ventricular volume (cm:')
Left ventricular volume (cm3)
Valve-apex distance (mm)
239.0
(n
1309
1431
±
=
±
±
52.7
5)
254
163
Control
367.5
(n
851
833
±
=
±
±
26.3
6)
95
121
Normal
440.0
(«
964
955
±
=
±
±
P value
<0.01
18.7
6)
113
76
<0.01
<0.01
4.33 ± 1.04
3.58 ± 0.69
1.46 ± 0.04
2.08 ± 0.55
2.59 ± 0.70
1.26 ± 0.04
2.63 ± 0.35
2.41 ± 0.01
1.30 ± 0.00
<0.01
<0.05
<0.01
5.40 ± 0.16
2.99 ± 0.10
2.43 ± 0.13
4.78 ± 0.21
2.73 ± 0.37
2.05 ± 0.17
4.78 ± 0.10
2.46 ± 0.11
2.32 ± 0.07
<0.01
6.13 ± 0.28
3.42 ± 0.11
2.72 ± 0.29
5.07 ± 0.32
2.95 ± 0.36
2.12 ± 0.16
5.21 ± 0.11
2.69 ± 0.16
2.52 ± 0.27
<0.01
<0.05
<0.01
5.26 ± 0.33
2.87 ± 0.11
2.38 ± 0.36
4.55 ± 0.20
2.53 ± 0.26
2.01 ± 0.17
4.83 ± 0.22
2.39 ± 0.08
2.44 ± 0.30
<0.01
<0.05
3.97 ± 0.26
1.59 ± 0.10
2.59 ± 0.64
3.50 ± 0.05
1.53 ± 0.13
1.97 ± 0.16
4.05 ± 0.06
1.71 ± 0.28
2.34 ± 0.34
NS
NS
80%
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
NS*
60%
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
40%
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
20%
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
Values are expressed as mean ± SD. NS = not significant.
the normal group. Values for the latter two groups again
were not statistically different, but the internal radius of
the volume-hypertrophied left ventricle was significantly
greater. The wall thickness at the 60% valve-apex distance
Interior
Exterior
Volume Hypertrophy
Control
Normal
Valve lOO-i
80-
60-
o 40-
20-
Apex 0
2
3
4
Radius (mm)
FIGURE 1 Mean left ventricular shape in the pressure-hypertrophied groups of rats (in absolute values). Solid lines drawn
through mean radii of all groups. Vertical bars denote 99%
confidence limits of mean radii of all groups.
was also significantly greater in the volume-hypertrophied
hearts.
In terms of these results, the volume-hypertrophied left
ventricle seems to increase its size by increasing in all
three dimensions. An attempt was made to normalize the
data by dividing the external and internal radii by the
valve-to-apex distance. These results are shown in Table
2. After normalization, there was no real difference
among the three groups.
In the volume hypertrophy study, hematocrits were
determined on renal venous blood of most of the rats
(Table 3). The mean hematocrit in the volume-hypertrophied group was significantly lower than in the control
and normal groups. The rate of aortic pressure development was significantly higher in the anemic rats than in
the control and normal groups. The mean aortic blood
pressure of the anemic rats was significantly lower than
that in the other groups.
PRESSURE HYPERTROPHY
The body and ventricular weights and right and left
ventricular volumes are shown in Table 4. The ventricular
weights were significantly greater in the pressure-hypertrophied group than in the sham-operated or normal
group.
The right and left ventricular volumes were not significantly different among the three groups. As shown by the
valve-to-apex distances in table 4, the longitudinal axes
also were not significantly different.
The external and internal radii and wall thicknesses of
the left ventricle are shown in Table 4 and Figure 2. The
external radius of the pressure-hypertrophied hearts was
MORPHOLOGY OF HYPERTROPHIED RAT HEART/Lin et al.
833
TABLE 2 Normalized Left Ventricular Dimensions in the Volume-Hypertrophied, Control,
and Normal Groups of Rats (Ratio of Radii: Valve-Apex Distance)
Volume hypertrophy
Control
Normal
P value
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
Valve-apex distance (mm)
1.46 ± 0.04
1.26 ± 0.04
1.30 ± 0.00
<0.01
80%
ER/V-A
IR/V-A
WT/V-A
3.71 ± 0.11
2.03 ± 0.12
1.68 ± 0.04
3.79 ± 0.06
2.20 ± 0.24
1.63 ± 0.19
3.68 ± 0.08
1.89 ± 0.08
1.78 ± 0.07
NS
NS
60%
ER/V-A
IR/V-A
WT/V-A
4.19 ± 0.15
2.34 ± 0.13
1.85 ± 0.16
4.02 ± 0.14
2.34 ± 0.23
1.68 ± 0.25
4.01 ± 0.08
2.07 ± 0.12
1.95 ± 0.21
NS
NS
NS
40%
ER/V-A
IR/V-A
WT/V-A
3.70 ± 0.23
1.97 ± 0.31
1.73 ± 0.31
3.60 ± 0.08
2.01 ± 0.16
1.60 ± 0.16
3.71 ± 0.17
1.89 ± 0.19
1.91 ± 0.19
NS
NS
20%
ER/V-A
IR/V-A
WT/V-A
2.71 ± 0.17
1.07 ± 0.06
1.64 ± 0.17
2.78 ± 0.08
1.22 ± 0.12
1.55 ± 0.12
3.11 ± 0.04
1.31 ± 0.21
1.80 ± 0.25
<0.01
NS
Values are expressed as mean ± SD; ER = external radius; V-A
WT = wall thickness; NS = not significant.
significantly greater at the 80%, 60%, and 40% levels.
However, there were no significant differences among the
three groups at the 20% level. When the internal radii
were compared at the 80%, 60%, 40%, and 20% levels
of the valve-to-apex distance, no significant differences
were found. The wall thickness in the pressure-hypertrophied group was substantially thicker than in the shamoperated and normal hearts (Table 4).
In order to distinguish the shapes of the left ventricles
among the pressure-hypertrophied, sham-operated, and
normal groups, the data from Table 4 are plotted in
Figure 2. The shapes of the normalized internal radii
were quite similar within the three groups (99% confidence limits are given at each point). However, the
normalized external radii of the pressure-hypertrophied
ventricle were substantially greater at 80%, 60%, and
40% of the valve-to-apex distance. As expected, the
shapes were very similar for the sham-operated and nor-
valve-to-apex distance; 1R = internal radius;
mal ventricles. The wall thickness in the hypertrophied
ventricle was greater than in the sham-operated and
normal groups at the 80%, 60%, and 40% levels.
Discussion
The weight of the paired ventricles of the pressurehypertrophied hearts was increased by 34% above that of
the sham-operated group. This value is somewhat less
than that reported (50%) by Spann et al.13 for the
pressure-hypertrophied cat right ventricle, but it is higher
than that reported by Grimm et al.10 and Kerr et al.14 The
mean carotid blood pressure of the rats with hypertrophied hearts was 136 ± 7.5 mm Hg, whereas the mean
carotid blood pressure was 102 ± 1.8 mm Hg in the
sham-operated rats. Carotid blood pressure increased by
34%, a value identical to the increase in ventricular
weight. Though the evidence may suggest that the enlargement of the pressure-hypertrophied ventricles compen-
3 Relationship of Hematocrit, Mean Aortic Pressure, and Pulse Rate in
Volume-Hypertrophied, Control, and Normal Rats
TABLE
Volume hypertrophy
Control
Normal
P value
20.0 ± 3.0
(10)
47.9 ± 5.9
(9)
50.6 ± 3.7
(9)
<0.01
Rate of pressure development (mm Hg/sec)
996 ± 142
(7)
506 ± 67
(8)
608 ± 65
(4)
<0.01
Mean aortic pressure (mm Hg)
71 ± 15
(9)
97 ± 9
(7)
96 ± 8
(6)
<0.01
Pulse rate (beats/min)
308.6 ± 24.6
(5)
255.5 ± 19.1
(4)
299.7 ± 14.5
(4)
<0.05
Body weight (g)
230.8 ± 54.0
(12)
278.8 ± 14.7
(9)
385.6 ± 25.9
(9)
<0.01
Hematocrit (%)
Values are expressed as mean ± SD. Numbers in parentheses denote the number of observations.
CIRCULATION RESEARCH
834
VOL. 41, No. 6, DECEMBER
1977
TABLE 4 Ventricular Dimensions in the Pressure-Hypertrophied, Sham-Operated, and
Normal Groups of Rats
Body weight (g)
Ventricular weight (mg)
Calculated ventricular weight
( m g)
3
)
Right ventricular volume (cm
Left ventricular volume (cm3)
Valve-apex distance (mm)
Pressure hypertrophy
Sham operated
Normal
P value
405.5 ± 18.1
(10)
1202 ± 14]
1259.7 ± 165
410.0 ± 12.9
425.0 ± 17.6
NS
(4)
(8)
896 ± 76
817 ± 16
922 ± 30
892 ± 131
<0.01
<0.01
3.24 ± 0.99
3.89 ± 0.87
1.32 ± 0.10
2.11 ± 0.50
3.15 ± 0.36
1.25 ± 0.05
3.14 ± 1.36
3.85 ± 1.80
1.33 ± 0.04
NS
NS
NS
5.75 ± 0.22
3.21 ± 0.33
2.53 ± 0.51
4.70 + 0.26
2.77 ± 0.04
1.93 i 0.23
4.89 ± 0.04
2.92 ± 0.12
1.97 ± 0.17
<0.01
5.96 ± 0.26
3.42 ± 0.38
2.54 ± 0.35
5.07 ± 0.19
3.16 i 0.16
1.91 ± 0.16
5.12 ± 0.02
2.99 ± 0.01
2.13 ± 0.01
5.36 ± 0.10
2.88 ± 0.28
2.48 ± 0.33
4.63 ± 0.23
2.73 ± 0.16
1.90 ± 0.13
4.70 ± 0.15
2.60 ± 0.14
2.10 ± 0.07
<0.01
4.03 ± 0.26
1.67 ± 0.31
2.36 ± 0.24
3.63 ± 0.50
1.76 ± 0.44
1.87 ± 0.09
3.82 ± 0.13
1.64 ± 0.07
2.18 ± 0.06
NS
NS
80%
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
NS
<0.01
60%
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
<0.01
NS
<0.01
40%
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
NS
<0.01
20%
External radius (mm)
Internal radius (mm)
Wall thickness (mm)
sated for the increased resistance, the influences of other
likely important factors such as time-wall stress probably
should be considered.
In the volume-hypertrophied hearts, ventricular weight
increased by 54% above the control value (Table 1). The
hematocrit was decreased by about 42% and the mean
Interior
Valve lOO-i
Apex
Exterior
o Pressure Hypertrophy
A Sham Operated
Normal
0
1
2
3
4
Radius (mm)
FIGURE 2 Mean left ventricular shape in the volume-hypertrophied groups of rats (absolute values). Solid lines drawn through
mean radii of all groups. Vertical bars denote 99% confidence
limits of mean radii of all groups.
<0.01
aortic blood pressure was much lower in the rats with
volume-hypertrophied hearts than in the controls. The
rate of aortic pressure development was increased substantially in the rats with volume-hypertrophied hearts.
This increase is probably the result of factors such as the
decreased mean aortic pressures and the decreased viscosity of the blood.
The functional morphology of the heart in terms of its
radius, volume, wall thickness, pressure, and tension,
etc., has been a subject of interest. Since the above
parameters are changing constantly during each cardiac
cycle, a major difficulty exists in selecting an acceptable
reference position from which morphological comparisons
may be made. It has been shown that a potassium-arrested-, formalin-fixed dog heart is indeed a "diastolelike" heart.8 The gelatin-embedding techniques used in
the present study produce relatively little distortion. In
previous work using living isolated papillary muscles, K+
arrest and formalin fixation produced only minimal
changes in sarcomere length.15 In addition, the thorax
was not opened nor were its contents disturbed. Thus,
the present techniques appear to overcome many limitations. It should be emphasized that the technique is being
used for comparative geometric considerations.
The data in Tables 1 and 4 show that the geometric
pattern of both the pressure-hypertrophied and volumehypertrophied ventricles are different, not only from the
normal, but also from each other. The differences could
be interpreted as resulting from the quite different factors
involved in the induction of the two types of hypertrophy.
As expressed by the Laplace relationship, the stress
generated in the ventricular wall is directly proportional
to the radius of the lumen and to the transmural pressure.
MORPHOLOGY OF HYPERTROPHIED RAT HEART/Lm el al.
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
If the internal radius of the left ventricle increases, the
wall stress will be proportionally increased under conditions of the same intraventricular pressures. This increase
in wall stress may be compensated for by an increase in
wall thickness, provided the geometry of the heart does
not change; this condition is seen in the volume-hypertrophied hearts. Since the pressure-hypertrophied left ventricle pumps against an increased resistance, the wall stress
must be increased to develop greater transmural pressure.
In rats with pressure-hypertrophied hearts, ventricular
lumen size remained unchanged. Table 4 shows that the
increasing size of the pressure-hypertrophied ventricle
was accompanied only by an increase in external radii,
whereas the luminal and the longitudinal dimensions
remained unchanged. Thus, the wall thickness and the
wall thickness-to-radius ratio were significantly increased.
These findings seem to agree with those of Levine et al.16
who noted that the ratio of the left ventricular diameter
to wall thickness was distinctly low in patients with left
ventricular pressure overload. The increase in wall thickness was equivalent to the increase in measured blood
pressure. We conclude that the induced hypertrophy was
able to reduce stress per unit of muscle to normal levels.
On the other hand, in the volume-hypertrophied hearts,
different factors were involved. The volume-hypertrophied left ventricle pumps a large amount of blood against
a lower peripheral resistance. Under these conditions,
both the ventricular lumen and the cardiac mass are
increased. The increase in wall thickness is proportionate
with the increase in luminal radius. The data presented in
Table 1 are represented graphically in Figure 1 to illustrate
that the cardiac size is increased both longitudinally and
transversely. The volume-hypertrophied heart thus appears as a magnified normal heart. Results given in Table
2 show that there were no significant differences among
the three groups of rats in terms of the shape of the
hearts after data was normalized. Thus wall thickness was
increased in proportion to the increase in ventricular size.
The wall thickness-radius ratio remained the same. This
result is very similar to those of Grant et al.17 and
Grossman et al.18 for subjects with aortic insufficiency.
They concluded that volume-overloaded ventricles
showed eccentric hypertrophy with an increased diameter
but normal wall thickness-radius ratios.
It has been found that mean sarcomere length does not
change from normal in either the pressure-overloaded or
the volume-overloaded hypertrophied myocardium. In
addition, the shapes of the length-tension curves are
identical as are the tensions when normalized on the basis
of grams/unit area.19 Taken together with the present
study, these results suggest that the unit quality (sarcomere length-mechanics and/or contractility) of the volume-hypertrophied myocardium is unchanged.
In a previous study, Grimm et al." found that over an
almost 3-fold range of ventricular weights, normal cardiac
growth was accompanied by an increase in linear dimensions such as valve-to-apex distance, external radius,
internal radius, and wall thickness. Although these distances increase with growth, the shape of the heart
remains unchanged. With normal physiological growth,
the increase in ventricular volume was apparently bal-
Volve
nterior
835
Exterior
+ Grimm's Doto
B Normal
A Sham Operated
H
0.2
0.3 04
0.5
Radius/ Height
1
0.6
FIGURE 3 Mean left ventricular shape among Grimm's normal
group and normal and control groups in the pressure- and volumehypertrophied rats (normalized values). Solid lines drawn through
mean radii of all groups. Vertical bars denote 99% confidence
limits of mean radii of all groups.
anced by a proportionate increase in wall thickness. For
the purpose of discussion, Figure 3 incorporates data
from Grimm et al.11 with data from the present study.
There are no significant differences. The previously derived equation, Y(100) = 128.2 + 0.175 X (F = 53.7; P
< 0.001) (r = 0.96), where Y is the left ventricular
radius and X is the paired ventricular weights with a
mean paired ventricular weight of 1295.1 mg for the
volume-hypertrophied heart, predicts a mean radius of
3.5 mm, a value almost identical to the 3.4 mm found.
In summary, the ventricular shape, wall thickness, and
external radii are significantly increased, whereas the
valve-to-apex distance and internal radii remain unchanged in the pressure-hypertrophied ventricle. Thus
external dimensions increase while internal "luminal dimensions" remain unchanged in this type of hypertrophy.
In the volume-hypertrophied ventricles, there is an increase in valve-to-apex distance, external radius, internal
radius, and wall thickness; thus both external and internal
dimensions increase; however, the ventricular shape does
not change significantly. The volume-hypertrophied ventricle preserves a normal functional morphology.
Acknowledgments
We thank Betsy R. Grimm for her valuable manuscript assistance.
References
1. Woods RH: A few applications of a physical theorem to membranes
in the human body in a state of tension. J Anat Physiol 26: 362-370,
1892
2. Burton AC: The importance of the size and shape of the heart. Am
Heart J 54: 801-810, 1957
3. Rushmer RF: Length-circumference relations of the left ventricle.
Circ Res 3: 639-644, 1955
4. Hawthorne EW: Dynamic geometry of the left ventricle. Am J
Cardiol 18: 566-573, 1966
5. Holt JP, Kines H, Rhode EA: Pattern of function of left ventricle of
mammals. Am J Physiol 209: 22-32, 1965
836
CIRCULATION RESEARCH
6. Martin RR, Haines H: Application of Laplace's law to mammalian
hearts. Comp Biochem Physiol 34: 959-962, 1970
7. Meerson F: The myocardium in hyperfunction, hypertrophy, and
heart failure. Circ Res 25 (Suppl 2): 1-163, 1969
8. Grimm AF, Lendrum BL, Whitehorn WV: Cardiac muscle shortening
and sarcomere lengths in the dog (abstr). Fed Proc 27: 697, 1968
9. Korecky B, French IW: Nucleic acid synthesis in enlarged hearts of
rats with nutritional anemia. Circ Res 21: 635-640, 1967
10. Grimm AF, Kubota R, Whitehorn WV: Properties of the myocardium
in cardiomegaly. Circ Res 12: 118-124, 1963
11. Grimm AF, Katele KV, Klein SA, Lin Hun-Lin: Growth of rat
heart —left ventricular morphology and sarcomere lengths. Growth
37: 189-208,1973
12. Sokal RR, Rohlf F James: Introduction to analysis of variance. In
Biometry, edited by R Emerson, D Kennedy, RB Park. San Francisco, W. H. Freeman, 1969, pp 175-203
13. Spann JF, Buccino RA, Sonnenblick EH, Braunwald E: Contractile
state of cardiac muscle obtained from cats with experimentally produced ventricular hypertrophy and heart failure. Circ Res 21: 341-
VOL. 41, No. 6, DECEMBER
1977
354,1967
14. Kerr A Jr, Winterberger AR, Giambattista M: Tension developed by
papillary muscles from hypertrophied rat hearts. Circ Res 9: 103105,1961
15. Grimm AF, Wohlfart B: Sarcomere lengths at the peak of the lengthtension curve in living and fixed rat papillary muscle. Acta Physiol
Scand92: 575-577, 1974
16. Levine ND, Rockoff SD, Braunwald E: An angiocardiographic analysis of the thickness of the left ventricular wall and cavity in aortic
stenosis and other valvular lesions. Circulation 28: 339-345, 1963
17. Grant C, Greene DG, Bunnell IL: Left ventricular enlargement and
hypertrophy; clinical angioradiographic study. Am J Med 39: 895904,1965
18. Grossman W, Jones D, McLaurin LP: Wall stress and patterns of
hypertrophy in the human left ventricle. J Clin Invest 56: 56-64,
1975
19. Lin H-L: A physiological, histological and biochemical study of the
pressure and volume hypertrophied rat myocardium. Ph.D. Thesis,
University of Illinois at the Medical Center, 1974
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
The Nature of Disappearance of Creatine Kinase
from the Circulation and Its Influence on
Enzymatic Estimation of Infarct Size
BURTON E. SOBEL, JOANNE MARKHAM, RONALD P. KARLSBERG, AND ROBERT ROBERTS
SUMMARY Continued progress in estimating myocardial ischemic injury from analysis of plasma enzyme timeactivity curves requires improved characterization of processes affecting release from the heart, transport, and
disappearance from the circulation. To determine whether the true disappearance rate (ka) of creatine kinase (CK)
is accurately reflected by the rate of elimination (k,,) from blood, we evaluated time-activity curves in 40 conscious
dogs after induced myocardial infarction, bolus injection, or slow intravenous infusion of CK extracted from
myocardium and CK harvested from plasma. The two CK preparations were compared by cellulose acetate
electrophoresis, radioimmunoassay, gel chromatography, and stability in vitro. Plasma CK time-activity curves after
intravenous injections of CK conformed more closely to double than to single-exponential curves (with avergage
standard deviations only 42% as large), suggesting distribution in at least one extravascular compartment.
Parameters of a two-compartment model obtained from the double-exponential curve provided estimates of k^
markedly greater than k,,. Calculations based on observed plasma values and these estimates of kj accounted for 2fold more CK released from the heart after infarction than that accounted for by calculations utilizing k,. The
decline of plasma CK after myocardial infarction was 60% slower than the decline after intravenous injections of
enzyme. The relatively slow decline after myocardial infarction appears to be due both to differences between
enzyme extracted from the heart and enzyme released endogenously into plasma and to continuing release of CK
from the ischemic heart relatively late after coronary occlusion.
INFARCT SIZE has been estimated from plasma creatine
kinase (CK) time-activity curves with a simple model
attributing serial changes in plasma CK activity to release
from the heart and concomitant disappearance from the
circulation.'"4 However, several factors are not encompassed by this approach1-2-*~9 including: (1) potential
From the Cardiovascular Division and Biomedical Computer Laboratory, Washington University School of Medicine. St. Louis, Missouri.
Research from the authors' laboratory was supported in part by
National Institutes of Health Grants HL 176446, SCOR in Ischemic
Heart Disease; HL 07081, Multidisciplinary Heart and Vascular Diseases;
and RR 00396.
Address for reprints: Burton E. Sobel, M.D., Director, Cardiovascular
Division, Washington University School of Medicine, 660 South Euclid
Avenue, St. Louis, Missouri 63110.
Received January 27, 1977; accepted for publication June 1, 1977.
contributions of isoenzymes of CK with different disappearance rates to plasma CK activity after myocardial
infarction; (2) potential variations of the true disappearance rate of CK within the same experimental animal or
patient during the interval of study; (3) the relatively
poor conformity of CK time-activity curves after intravenous injection to single-exponential fits; and (4) the
possibility that CK, like many other proteins, is distributed
in at least one extravascular compartment.
With the development of quantitative assays for CK
isoenzymes, the first pitfall could be avoided by analyzing
MB ('myocardial') CK time-activity curves rather than
total CK curves in patients.10 In dogs, since myocardium
contains only a modest amount of MB (<2%) 10 and since
plasma CK activity after infarction is attributable primarily
Functional morphology of the pressure- and the volume-hypertrophied rat heart.
H L Lin, K V Katele and A F Grimm
Downloaded from http://circres.ahajournals.org/ by guest on June 11, 2017
Circ Res. 1977;41:830-836
doi: 10.1161/01.RES.41.6.830
Circulation Research is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1977 American Heart Association, Inc. All rights reserved.
Print ISSN: 0009-7330. Online ISSN: 1524-4571
The online version of this article, along with updated information and services, is located on the
World Wide Web at:
http://circres.ahajournals.org/content/41/6/830
Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in
Circulation Research can be obtained via RightsLink, a service of the Copyright Clearance Center, not the
Editorial Office. Once the online version of the published article for which permission is being requested is
located, click Request Permissions in the middle column of the Web page under Services. Further information
about this process is available in the Permissions and Rights Question and Answer document.
Reprints: Information about reprints can be found online at:
http://www.lww.com/reprints
Subscriptions: Information about subscribing to Circulation Research is online at:
http://circres.ahajournals.org//subscriptions/