2267
Effect of Inotropic Stimulation on the Negative
Force-Frequency Relationship in the
Failing Human Heart
Robert H.G. Schwinger, MD; Michael Bohm, MD; Jochen Muller-Ehmsen, MS;
Rainer Uhlmann, PhD; Ulrich Schmidt, MS; Alexander Stablein, MD; Peter Uberfuhr, MD;
Eckhart Kreuzer, MD; Bruno Reichart, MD; Hans-Joachim Eissner, MD; Erland Erdmann, MD
Background. In severe human heart failure, an increase in frequency of stimulation is accompanied by
reduced force of contraction in vivo and in vitro. The present study was aimed to investigate whether
inotropic stimulation influences the inverse force-frequency relationship in failing human myocardium.
Methods and Results. The effects of the cAMP-independent positive inotropic agents ouabain (0.01
,imol/L) and BDF 9148 (0.1 ,umol/L) as well as the 3-adrenoceptor agonist isoprenaline (0.01 ,umol/L
and 0.1 ,umol/L) on the force-frequency relationship in electrically driven papillary muscle strips from
nonfailing (brain death, n=5) and terminally failing (NYHA class IV, heart transplants, dilated
cardiomyopathy, n=22) human myocardium were studied. For comparison, we examined the effect of
elevation of the extracellular Ca2' concentration (3.2 mmol/L and 6.2 mmol/L). In nonfailing myocardium, force of contraction, peak rate of tension rise, and peak rate of tension decay increased, whereas
time to peak tension and time to half relaxation decreased following an increase of stimulation frequency.
In NYHA class IV, force of contraction gradually declined followed by changes of other parameters of
isometric contraction. Moderate stimulation of contractility by isoprenaline (0.01 ,umol/L) partly reversed
the negative force-frequency relationship in NYHA class IV and preserved the positive force-frequency
relationship in nonfailing myocardium. The addition of ouabain and BDF 9148 together restored
completely the force-frequency relationship in NYHA class IV. In contrast, high concentrations of
isoprenaline (0.1 ,umol/L) and an elevation of the extracellular Ca2' concentration enhanced the decline
in force of contraction in the presence of higher stimulation frequencies.
Conclusions. It is concluded that functionally important changes occur in the intracellular Ca2'
handling, leading to the negative force-frequency relationship in terminally failing human myocardium.
Interestingly, the negative force-frequency relationship can be restored by agents producing positive
inotropic effects by elevation of the intracellular Na+ concentration. These findings suggest that hitherto
unknown changes in the intracellular ionic homeostasis occur in the failing human heart. Even though
increasing [Ca2"J1 in failing heart cells may be detrimental, increasing [Na+], may be beneficial through
a mechanism independent of an increase in [Ca2+J1. (Circulation. 1993;88[part 11:2267-2276.)
KEY WORDs * myocardium * heart failure * force-frequency relationship * ouabain
a
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
Several investigators demonstrated an altered
force-frequency relationship in failing human
thlmyocardium.'-7 In these studies, force of contraction increased in nonfailing myocardium but not in
diseased human myocardial tissue following an increase
of stimulation frequency. Similar findings have been
reported in vivo.8 Rapid atrial pacing in patients with
heart failure due to dilated cardiomyopathy produced
no change in peak rate of left ventricular pressure rise
(dp/dtmax), whereas in control subjects dp/dtma, inReceived August 31, 1992; revision accepted May 28, 1993.
From the Klinik III fur Innere Medizin der Universitat zu Koin
(R.H.G.S., M.B., J.M.-E., R.U., U.S., A.S., E.E.), the Herzchirurgische Klinik der Universitat Munchen (P.U., E.K., B.R.), and the
Institut fur Medizinische Informationsverarbeitung, Biometrie
und Epidemiologie, Klinikum Grosshadern (H.-J.E.), Munchen,
Germany.
Reprint requests to Dr Robert H.G. Schwinger, Klinik III fur
Innere Medizin der Universitat zu KoIn, Joseph-Stelzmannstr. 9,
50924, KoIn, Germany.
creased by 30% when stimulation frequency increased
from 1.3 Hz to 2 Hz. In addition to the well-studied
downregulation of myocardial /8-adrenoceptors,9 increased levels of inhibitory guanine nucleotide binding
proteins,101' and reduced basal cAMP levels,'213 the
depressed force-frequency relationship in failing human
myocardium could contribute significantly to the impaired exercise tolerance in heart failure patients. Experimental studies suggested that the negative forcefrequency relationship in failing human myocardium is
likely to be due to alterations of the intracellular Ca2'
handling.4'6"14-'6 Consistently, differences in intracellular
Ca2' handling have been reported in isolated myocardial cells from patients with dilated cardiomyopathy in
comparison to control cells.14
Both cAMP-dependent as well as cAMP-independent positive inotropic compounds influence intracellular Ca 2+ handling. Thus, one could suggest that these
agents could affect the altered force-frequency relationship in the failing heart favorably or adversely. In
2268
Circulation Vol 88, No 5, Part 1 November 1993
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
addition, agents with different mechanisms of action
could also be an interesting tool to investigate the
underlying pathophysiological changes. Therefore, the
present study was aimed to investigate the influence of
cAMP-dependent and cAMP-independent inotropic
stimulation in human failing and nonfailing myocardium
on the force-frequency relationship. Cardiac glycosides
are believed to act by inhibiting the membrane-bound
NaXK+-ATPase,17 leading to an increase of the intracellular Na' concentration that in turn activates the
Na+/Ca2' exchange mechanism18 to increase intracellular Ca2`. The Na' channel activator BDF 9148 has been
reported to enhance sensitivity of failing and nonfailing
human myocardium to ouabain,19 probably by an elevation of the intracellular Na' load.20 Therefore, in the
presence of the Na' channel activator BDF 9148, the
effects of low concentrations of ouabain (0.01 ,umol/L)
can be studied under in vitro conditions. This is important because the plasma concentrations of ouabain are
much lower than the concentrations producing positive
inotropic effects in vitro. Therefore, the effects on the
parameters of the isometric contraction at different
stimulation frequencies were studied under basal conditions and following a moderate increase of force of
contraction by ouabain (low concentration) plus BDF
9148. cAMP-dependent and cAMP-independent positive inotropic stimulation was performed with isoprenaline and Ca2+, respectively.
Methods
Myocardial Tissue
Experiments were performed on isolated, electrically
stimulated papillary muscle strips from human left
ventricular myocardium. Tissue was obtained during
cardiac transplantation (n=22, 7 women and 15 men;
mean age, 54.4±3.5 years; range, 24 to 64 years; dilated
cardiomyopathy; hemodynamic data, left ventricular
end-diastolic pressure of 22±2.0 mm Hg, left ventricular volume of 290±42 mL, ejection fraction of 24±2.0%,
cardiac index of 2.6±0.3 L. m2 * min-1). Patients suffered from heart failure clinically classified as NYHA
IV on the basis of clinical symptoms and signs as judged
by the attending cardiologist shortly before surgery. All
patients gave written informed consent before surgery.
Medical therapy consisted of diuretics, nitrates, angiotensin converting enzyme inhibitors, and cardiac glycosides. Patients receiving catecholamines or 13-adrenoceptor or Ca2' antagonists were withdrawn from the
study. Drugs used for general anesthesia were flunitrazepam and pancuroniumbromide with isoflurane.
Cardiac surgery was performed on cardiopulmonary
bypass with cardioplegic arrest during hypothermia.
Nonfailing human myocardium (control) was obtained
from 5 donors who were brain dead as a result of
traumatic injury. To identify these hearts as controls,
the clinical situation prior to death was considered.
Data gave the information that the heart was useful as
a donor heart to the attending cardiologist and to the
cardiac surgeon explanting the heart. There was no
evidence for left ventricular dysfunction by echocardiography. These hearts could not be transplanted for
technical reasons. The number of .8-adrenoceptors also
was measured. It has been demonstrated that the number of 83-adrenoceptors is decreased in failing human
myocardium. Also, the maximal increase in force of
contraction following stimulation with isoprenaline has
been examined. Histological examination was performed to identify myocardial diseases. Immediately
after explantation, the myocardial tissues were placed in
ice-cold preaerated modified Tyrode's solution (composition below) and delivered to the laboratory within 10
minutes. The cardioplegic solution (a modified
Bretschneider solution) contained (in mmol/L): NaCl
15, KCl 10, MgCl2 4, histidine 180, tryptophan 2,
mannitol 30, and potassium dihydrogen oxoglutarate 1.
Contraction Experiments
Immediately after excision, the papillary muscles were
placed in ice-cold preaerated modified Tyrode's solution
(composition below) and delivered to the laboratory
within 10 minutes. The experiments were performed on
isolated, electrically driven (1 Hz) muscle preparations.
Muscle strips of uniform size with muscle fibers running
approximately parallel to the length of the strips were
dissected under microscopic control using scissors in aerated bathing solution (composition below) at room temperature. Connective tissue, if visibly present, had to be
carefully trimmed away. Histological examination revealed
no differences for fibrous tissue between nonfailing and
failing myocardium in the muscle strip preparation used.
Myocardial tissue (1.1+0.2x1.0±0.3 cm, three or four
different samples from each heart) was stored in formalin.
Afterward, microscopic sections (5 to 6 gm) were examined that had been prepared as haemalain-eosin (H.E.) or
van Gieson stain. We measured the weight of the preparations used (the muscle strip preparations were blotted
dry, 10 g for 1 minute). Cross-sectional area was estimated
on the basis of weight, assuming the muscle to be a
cylinder with a specific gravity of 1, and was determined
from papillary muscle diameter by the formula XS=
3.14159x(D/2)2 (where XS is cross-sectional area and D is
diameter). The corresponding data in failing and nonfailing human myocardium were 0.59±0.06 mm2 and
0.60±0.07 mm2. Cross-sectional area and weight of the
muscle preparations were not different in preparations
from failing and nonfailing myocardium in any experimental condition tested.
The preparations were attached to a bipolar platinum
stimulating electrode and suspended individually in
75-mL glass tissue chambers for recording of isometric
contractions. The bathing solution used was a modified
Tyrode's solution containing (in mmol/L): NaCl 119.8,
KCl 5.4, CaCl2 1.8, MgCl2 1.05, NaH2PO4 0.42, NaHCO3
22.6, Na2EDTA 0.05, ascorbic acid 0.28, and glucose 5.0.
It was continuously gassed with 95% 02-5% CO2 and
maintained at 37°C; its pH was 7.4. Isometric force of
contraction was measured with an inductive force transducer (W. Fleck, Mainz, FRG) attached to a Hellige
Helco Scriptor (Hellige, Freiburg, FRG) or Gould
recorder (Gould Inc, Cleveland, Ohio). The rate of
tension change was determined by differentiation of the
force signal. Each muscle was stretched to the length at
which force of contraction was maximal. To obtain
comparable experimental conditions, these basal conditions were kept constant. The preparations were electrically paced at 1 Hz with rectangular pulses of 5 -milliseconds' duration (Grass stimulator SD 9); the voltage
was 20% above threshold. All preparations were allowed to equilibrate at least 90 minutes in a drug-free
Schwinger et al Human Myocardium and Force-Frequency Relationship
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
bathing solution (1 Hz) until complete mechanical
stabilization. After 45 minutes, the solution was
changed. After complete mechanical stabilization, the
force-frequency relationship was studied, starting with a
rate of 0.5 Hz. The duration of stimulation for a given
frequency was constant (5 minutes) until complete
stabilization of force development. The force-frequency-dependent effects were determined, that is, force of
contraction (FOC), peak rate of tension rise (+T), peak
rate of tension decay (-T), time to peak tension (TPT),
and time to half-relaxation (T1/2T). Control strips
showed no change in baseline isometric tension during
the period of time necessary to complete pharmacologic
testing. Inotropic interventions were performed at 1 Hz.
Compounds were added as described previously.19 Afterward, the force-frequency relation was studied in the
same way as under basal conditions. Each pharmacologic intervention was studied using a separate papillary
muscle strip. At the end of the experiments, maximal
force development was studied using CaCl2 (15 mmol/
L). There was no difference in force generation between
groups. Moreover, in preparations from each group at
the end of the experiments, the carbogen was changed
to 80% 02-5% C02-15% N221 at the stimulation rate,
where force development was maximal. Muscle strips
showing a decline more than 10% during 30 minutes
were excluded.
Materials
BDF 9148 (4-(3-(1-diphenylmethyl-azetidin-3-oxy)2-hydroxy-propoxy)-1 H-indol-2-carbonitril) was kindly
provided from Beiersdorf AG (Hamburg, FRG). Ouabain was obtained from Boehringer (Mannheim, FRG)
and isoprenaline from Sigma Chemical Co (Deisenhofen, FRG). All other chemicals were of analytic grade or
the best grade commercially available. For studies with
isolated cardiac preparations, stock solutions were prepared and applied to the organ bath. BDF 9148 was
dissolved in 50% DMSO. The final concentration of
DMSO in the bathing solution never exceeded 0.05%.
All other compounds were dissolved in twice-distilled
water. Applied agents did not change the pH of the
medium.
Statistical Analysis
Differences in the shape of the force-frequency relation in failing and nonfailing human tissue were analyzed between the following groups: group A: failing
myocardium, basal condition; group B: failing myocardium, BDF 9148 and ouabain; group C: nonfailing
myocardium, basal condition; and group D: nonfailing
myocardium, BDF 9148 and ouabain. The following
four group comparisons were done: comparison of the
outcomes in group A with those in group B and outcomes in group C with those in group D tested the effect
of the inotropic stimulation in failing and nonfailing
myocardium; comparison of the outcomes in group A
with those in group C and outcomes in group B with
those in group D tested the differences between failing
and nonfailing myocardium under basal conditions and
with inotropic stimulation. Outcome measures were the
changes of force of contraction obtained when the
stimulation frequency was stepwise increased. Five
steps were considered: (1) from 0.5 Hz to 1.0 Hz, (2)
from 1 Hz to 1.5 Hz, (3) from 1.5 Hz to 2.0 Hz, (4) from
E
2269
3-
2
C] Nonfailing
A NYHA IV
0.5
10.
15
2.0
2.5
3.0
Frequency (Hz)
FIG 1. Plot of force of contraction (ordinate, mN) plotted
as a function of frequency of stimulation (0.5 Hz to 3 Hz,
abscissa) in electrically driven papillary muscle strips
from nonfailing and terminally failing myocardium. The
number of strips studied was 58 in the failing and 13 in
the nonfailing group. Basal force of contraction is given in
Table 1. Data shown are mean±95% confidence limit.
2 Hz to 2.5 Hz, and (5) from 2.5 Hz to 3.0 Hz. Each
comparison consisted of five two-sample t tests. To
adjust for the fact that a large number of tests were
made (four comparisons with five tests), Bonferroni's
correction was used; reported P values are multiplied by
20. The results remained unchanged, when the twosample median test was used to verify the levels of the
P values (this statistical method is applicable for both
normally and not-normally distributed data). An
ANOVA22 was used to compare the means of force of
contraction at 0.5-Hz stimulation. All tests were twotailed. The statistical analysis has been performed with
data presented in mN as well as with data presented in
mN/mm2. Results were not different between both ways
of evaluating the data. Results are presented as
mean±SEM (tables) or as means with 95% confidence
limits (figures). The programs of the SAS Institute were
used for all analyses (SAS Institute Inc, 1989).23 Other
parameters were analyzed using one-sample or twosample t tests.22 Results are presented as mean±SEM.
The statistical analysis was performed by the Department of Medical Information, Biometry and Epidemiology of the University of Munich.
Results
Force-Frequency Relationship in Failing and
Nonfailing Human Myocardium
Fig 1 shows the force-frequency relationship in failing
and nonfailing human myocardium from 0.5 Hz to 3 Hz.
Following an increase in stimulation frequency up to 3
Hz, force of contraction gradually increased in nonfailing myocardium. In contrast, in failing myocardium,
increase in the frequency of stimulation was accompanied by a reduction of force of contraction (Table 1). Fig
2 illustrates the changes in force development following
a change in stimulation frequency. There was a significant difference between both groups (Table 2). The
rate-dependent change in force of contraction in nonfailing and failing myocardium is demonstrated in the
original recordings given in Fig 3. All parameters of
isometric contraction were dependent on the stimulation frequency (Tables 3 and 4). There was an increase
of +T and -T in nonfailing myocardium but not in
tissue from patients with heart failure (Tables 3 and 4).
Circulation Vol 88, No 5, Part 1 November 1993
2270
HUMAN PAPILLARY MUSCLE STRIPS
068
a Nonfailing
04
NYHAIV
-
0.2.0 0
0
I-0.2-
0.01-.i
1.010.5
1.0-2.0
2.0-2.
2.0-.0
Change in frequency liz)
FIG 2. Bar graph of change in force of contraction
(ordinate, A mN) relative to changes in frequency of
stimulation (abscissa) in electrically driven papillary muscle strips from nonfailing and terminally failing myocardium. The number of strips studied was 58 in the failing
and 13 in the nonfailing group. The figure illustrates the
change in force of contraction following changes in
frequency of stimulation. (Please see also "Statistical
Analysis.") Data shown are mean+95% confidence limit.
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
In nonfailing myocardium, +T and -T increased and
TPT and T112T decreased following an increase in
stimulation rate. The relaxation was stimulated less
rapidly than contraction at higher frequencies. In failing
myocardium, the change in -T and +T was smaller
compared to nonfailing myocardium (Tables 3 and 4).
cAMP-Dependent Stimulation With Isoprenaline
To investigate the influence of cAMP-dependent
inotropic stimulation, 0.01 1Lmol/L and 0.1 1&mol/L
isoprenaline were applied to the organ bath prior to
examination of the force-frequency relationship in failing and nonfailing human myocardium (Figs 4 and 5).
After inotropic stimulation with 0.1 ,umol/L isoprenaline, the developed tensions in mN/mm2were 5.25±0.53
and 13.61±2.03 in failing and nonfailing human tissue
(0.5 Hz). The corresponding values for stimulation with
0.01 ,umol/L isoprenaline were 5.60±0.62 mN/mm2 and
4.30±0.63 mN/mm2, respectively. Isoprenaline (0.01
limol/L) increased force of contraction in nonfailing
myocardium by +1.0±0.3 mN and in failing myocardium by +0.5+0.2 mN, respectively. A low concentration of isoprenaline (0.01 pumol/L) did not influence the
force-frequency relationship in nonfailing myocardium
(Fig 4). Isoprenaline at 0.1 1£mol/L increased force of
contraction by +6.2± 1.0 mN in nonfailing and
+2.3±0.5 mN in failing myocardium. In the presence of
a high concentration (0.1 ttmol/L) of isoprenaline,
increasing frequency of stimulation was followed by a
decrease in force of contraction in the nonfailing myocardium (Fig 5). In NYHA class IV, in the presence of
0.01 ,umol/L, that is, low concentrations of isoprenaline,
the force-frequency relationship became positive (Fig
4). In contrast, in the presence of high concentrations of
isoprenaline (0.1 tumol/L) (Fig 5), the force-frequency
relationship was negative in NYHA class IV. Inasmuch
as rate of tension increase and decay are related to
developed force, we have examined the data in the low
isoprenaline condition. In failing human myocardium,
+T and -T increased in the presence of 0.01 ,umol/L
isoprenaline following an increase in stimulation frequency (Tables 3 and 4).
Stimulation With Ouabain and BDF 9148
Prestimulation with BDF 9148 enhances sensitivity of
human myocardium to ouabain.19 Therefore, we examined
the effect of moderate inotropic stimulation with ouabain
on the force-frequency relationship after pretreatment
TABLE 1. Influence of BDF 9148 and Ouabain on the Force-Frequency Relationship in Human Nonfailing
and Failing Myocardium
Left Ventricular Papillary Muscle Strips
Drug Free
mN
Tension,
mN/mm2
No.
1.7±0.2
2.1±0.3
2.7±0.3
3.1±0.3
3.2±0.2
3.0±0.2
4.0±0.6
4.9±0.7
6.3±0.8
7.3±0.8
7.3±0.6
6.9±0.6
2.4±0.2
2.1±0.1
2.0±0.1
1.8±0.1
1.7±0.1
1.4±0.1
(mN); and tension,
4.6±0.2
4.1±0.2
3.9±0.2
3.5±0.2
3.2±0.2
2.7±0.2
developed tension
FOC,
No.
BDF 9148+Ouabain
FOC,
mN
Tension,
mN/mm2
4
4
4
4
4
4
1.9±0.2
2.1±0.3
2.7±0.5
2.9±0.4
3.0±0.3
2.8±0.2
4.8±0.3
5.3±0.5
6.6±0.8
7.1±0.6
14
14
14
14
14
14
1.7±0.2
3.0±0.4
3.5±0.5
3.4±0.4
3.1±0.3
2.6±0.3
3.7±0.4
6.4±0.8
7.5±0.9
7.3±0.8
6.7±0.6
5.7±0.6
Nonfailing
0.5 Hz
13
1.0 Hz
13
Hz
1.5
13
2.0 Hz
13
2.5 Hz
13
3.0 Hz
13
Failing
0.5 Hz
58
1.0 Hz
58
1.5 Hz
58
2.0 Hz
58
2.5 Hz
58
3.0 Hz
58
FOC indicates force of contraction
(mN/mm2).
7.4+0.4
7.1±0.4
Schwinger et al Human Myocardium and Force-Frequency Relationship
2271
TABLE 2. Influence of BDF 9148 and Ouabain on the Force-Frequency Relationship in Human Nonfailing
and Failing Myocardium
Left Ventricular Papillary Muscle Strips
BDF 9148+Ouabain
Drug Free
A Tension
Nonfalling
0.5-1.0 Hz
1.0-1.5 Hz
1.5-2.0 Hz
2.0-2.5 Hz
2.5-3.0 Hz
A Tension
No.
A FOC (mN)
(mN/mm2)
No.
A FOC (mN)
(mN/mm2)
13
13
13
13
13
+0.37±0.07
+0.58±0.08
+0.42±0.06
+0.04±0.11
-0.18±0.07
+0.89±0.17
+1.35±0.19
+0.99±0.15
+0.09±0.28
-0.42±0.16
4
4
4
4
4
+0.19±0.14
+0.57±0.18
+0.18±0.07
+0.09±0.19
-0.15±0.16
+0.42±0.32
+1.39±0.37
+0.48±0.20
+0.29+0.48
-0.34±0.35
Failing
0.5-1.0 Hz
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
14
+2.71 ±0.55t
58
-0.21±0.05*
-0.44±0.10*
+1.28±0.27t
14
+1.12±0.30t
1.0-1.5 Hz
58
-0.28±0.08*
-0.15±0.04*
+0.52±0.15t
14
-0.11±0.17
-0.20±0.37
1.5-2.0 Hz
58
-0.17±0.02*
-0.32±0.04*
14
-0.33±0.11
-0.66±0.24
2.0-2.5 Hz
58
-0.18±0.03
-0.34±0.06
14
-0.47±0.11
-0.97±0.23
2.5-3.0 Hz
58
-0.26±0.04
-0.49±0.06
A FOC indicates change in force of contraction (mN); and A tension, change in developed tension (mN/mm2). *P<.01,
change in force of contraction/tension in failing vs nonfailing tissue. tP<.01, change in force of contraction/tension in failing
human myocardium with vs without pretreatment with BDF 9148 plus ouabain.
There was no statistically significant difference between failing and nonfailing tissue after pretreatment with BDF 9148
plus ouabain. (Please see also "Statistical Analysis.")
with BDF 9148 (0.1 gmol/L) (Figs 6 and 7). This experimental condition was used to investigate effects of agents
that increase intracellular sodium at concentrations with
only minor inotropic effectiveness. After inotropic stimulation with BDF 9148 and ouabain, the developed tensions
in mN/mm2 were 3.68+0.39 and 4.84±0.32 in failing and
nonfailing human myocardium (0.5 Hz). After BDF 9148
and ouabain were applied to the organ bath, force of
contraction increased by + 1.1±0.3 mN in the failing and
+0.4±0.2 mN in the nonfailing group, respectively. In the
presence of BDF 9148 and ouabain, force of contraction
(Figs 6 and 7), +T, and -T increased following an
increase in stimulation rate in both nonfailing and failing
myocardium (Tables 1, 3, and 4). Fig 8 shows changes in
force of contraction following changes in stimulation frequency with as well as without pretreatment with BDF
9148 and ouabain. In the presence of BDF 9148 plus
HUMAN PAPILLARY MUSCLE STRIPS
Navao Hen
Faling Heat
F.
O
Fi us. 0.5 HZ
ouabain, there was no statistically significant difference in
the force-frequency relationship between nonfailing and
failing myocardium (Fig 7). Therefore, ouabain in the
presence of BDF 9148 was effective in restoring the
positive force-frequency relationship in failing human
myocardium. Both agents exerted no detrimental effects in
nonfailing tissue at low concentrations, ie, after moderate
inotropic stimulation. At higher frequencies of stimulation
(above 1.5 Hz), +T and -T increased in nonfailing and
failing myocardium.
Effect of Ca 2+
Elevation of the extracellular Ca2' concentration was
effective in increasing force of contraction by 2.0±0.6
mN (3.2 mmol/L Ca2+) and +5.0±1.0 mN (6.5 mmol/L
Ca2+) in failing human myocardium. After inotropic
stimulation by elevation of the extracellular Ca 2+ concentration to 3.2 mmol/L and 6.2 mmol/L, the developed tensions in mN/mm2 were 8.77±2.36 and
16.28±3.26 (0.5 Hz). In the presence of elevated extracellular Ca2+ concentrations, increasing frequencies of
stimulation were accompanied by a pronounced decrease in force of contraction (Fig 9). Following an
increase in stimulation frequency, neither +T nor -T
was enhanced in failing human myocardium in the
presence of high extracellular Ca21 concentrations.
Discussion
2 Hz
3 Hz
FIG 3. Original recording of force of contraction in
electrically driven papillary muscle strips from nonfailing
and failing human myocardium at various stimulation
frequencies.
The present study provides evidence that pharmacologic interventions may restore the negative forcefrequency relationship in terminally failing human myocardium due to dilated cardiomyopathy and, thus, may
preserve the positive force-frequency relationship that
is observed in nonfailing human myocardium. This
2272
Circulation Vol 88, No 5, Part 1 November 1993
TABLE 3. Influence of Inotropic Compounds on Force-Frequency Relationship in
Nonfailing Myocardium
Left Ventricular Papillary Muscle Strips
Time Course Measurements
Nonfalling
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
No.
Basal
+T
12
-T
11
TPT
12
T1/2T
13
Isoprenaline 0.01
+T
3
-T
3
TPT
3
T1/2T
3
BDF 9148+Ouabain
+T
2
-T
2
TPT
2
2
T1/2T
+T indicates peak rate of tension rise (mN/s); -T,
(ms); and T1/2T, time to half tension decay (ms).
0.5 Hz
1 Hz
2 Hz
12±1.5
9±1.4
212±5.0
146±4.0
15±2.0
11±1.6
182±5.0
135±4.0
31±2.6
21±1.7
150±4.0
104±2.0
12±2.2
9±1.5
225±19.0
142±6.0
14±2.5
12±1.2
197±5.0
123±1.2
28±2.9
21±3.5
153±3.0
97±8.0
14±1.9
7±1.0
210±7.0
165±11.0
16±2.3
8±1.8
205±5.0
165±4.0
26±2.8
18±2.8
168±2.0
110±4.0
peak rate of tension decay (mN/s); TPT, time to peak tension
holds true for moderate inotropic stimulation with the
13-adrenoceptor agonist isoprenaline and the combination of BDF 9148 and ouabain, ie, agents that increase
the intracellular Na' concentration.20 Parameters of
isometric contraction, ie, peak rate of tension rise, peak
rate of tension decay, time to peak tension, and time to
half relaxation, were in good agreement with previously
published data.24
Effect of cAMP-Dependent Inotropic Stimulation
The positive force-frequency relationship has been
suggested to be due to changes in Ca21 content of the
TABLE 4. Influence of Inotropic Compounds on Force-Frequency Relationship in Human
Failing Myocardium
Left Ventricular Papillary Muscle Strips
Time Course Measurements
Failing
No.
0.5 Hz
1 Hz
2 Hz
Basal
+T
-T
TPT
T1/2T
32
32
32
32
19±2.0
15±1.7
203±5.0
133±4.0
19±1.8
13±1.3
183±4.0
125±4.0
21±2.0
13±1.4
146±3.0
106±2.0
Isoprenaline 0.01
+T
11
17±3.0
21±3.3
29±4.9
-T
11
14±3.4
17±3.5
23±4.8
11
TPT
190±9.0
179±7.0
143±6.0
11
114±4.0
95±4.0
125±4.0
T1/2T
BDF 9148+Ouabain
27±4.2
14±1.9
33±3.7
10
+T
22±2.9
-T
10
9±1.3
17±2.6
146±5.0
TPT
10
190±5.0
178±4.0
10
153±6.0
131±5.0
108+4.0
T1/2T
+T indicates peak rate of tension rise (mN/s); -T, peak rate of tension decay (mN/s); TPT, time to peak tension
(ms); and T1/2T, time to half tension decay (ms).
Schwinger et al Human Myocardium and Force-Frequency Relationship
HUMAN PAPILLARY MUSCLE STRIPS
8
HUMAN PAPILLARY MUSCLE STRIPS
NONFAILING
NONFAILING
E
E
8
6
3
5
co
8
2273
o Drug tree
* Isoprenallne 0.1pmoOl
2
0
St
3
0
1
2
o Drugre
IL
* Isoprenahe 0.01pmoVI
o
0.5
1.0
1.5
2.0
2.5
o
3.0
0.5
1.0
a
HUMAN PAPILLARY MUSCLE STRIPS
2.0
2.5
3.0
HUMAN PAPILLARY MUSCLE STRIPS
NYHA IV
NYHA IV
4
1.5
Frequency (Hz)
Frequency (Hz)
28
A Dg*ree
A Isopne
0
0.1 pmo
0
0
3
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
UsLL
A Ispen
o
0.01 pm
0.
0.5
1.0
1.5
2.0
2.5
3.0
Frequency (Hz)
FIG 4. Plots of force-frequency relationship under basal
condition (drug free) and after inotropic stimulation with
isoprenaline (0.01 gmol/L) in isolated electrically driven
papillary muscle strips from nonfailing (top) and terminally failing (bottom) myocardium. The number of strips
studied was 7 in the failing and 4 in the nonfailing group.
Basal force of contraction was 2.5+±0.4 and 2.7±0.4 mN
with as well as without pretreatment in failing tissue. The
corresponding values in nonfailing myocardium were
1.9±0.3 mN and 1.8±0.4 mN, respectively. The ordinate
gives force of contraction in mN relative to stimulation
frequency (abscissa, Hz). Data shown are mean±SEM.
sarcoplasmic reticulum, possibly as a result of changes
in net Ca2' influx into the cell secondary to an increase
in [Na+],.25 If a reduced Ca21 loading of the sarcoplasmic reticulum is the cause, then agents that facilitate
Ca2' reuptake would be beneficial. Stimulation of force
of contraction with low concentrations of isoprenaline
caused an increase in force of contraction following an
increase in stimulation rate in failing human myocardium with a former negative force-frequency relationship. This is in accordance with previous studies.5
Therefore, low concentrations of isoprenaline were
effective to restore the positive force-frequency relationship in failing myocardium and were able to preserve the "positive treppe" phenomenon observed in
nonfailing hearts. In contrast, prestimulation with high
concentrations of isoprenaline (0.1 gmol/L) resulted in
a pronounced negative force-frequency relationship in
both failing and nonfailing human myocardial tissue
(this study). Therefore, the increase in intracellular
cAMP and, hence, in Ca21 may have impaired the
force-frequency relationship. This holds true for both
failing and nonfailing myocardium. In failing myocardium, cAMP levels are reduced.12'13 Stimulation of
myocardial p-adrenoceptors increases intracellular
cAMP levels. In the presence of the /3-adrenoceptor
agonist isoprenaline or the diterpen derivate forskolin,
which also enhances cAMP and thereby facilitates sar-
0.5
1.0
1.5
2.0
2.5
3.0
Frequency (Hz)
FIG 5. Plots of force-frequency relationship under basal
condition and after inotropic stimulation with isoprenaline
(0.1 1£mol/L) in isolated electrically driven papillary muscle strips from nonfailing (top) and terminally failing
(bottom) myocardium. The number of strips studied was
7 in the failing and 4 in the nonfailing group. Basal force
of contraction was 3.4±0.4 and 1.7±0.1 mN with as well
as without pretreatment in failing tissue. The corresponding values in nonfailing myocardium were 7.5±1.3 and
1.8±0.2 mN, respectively. The ordinate gives force of
contraction in mN relative to stimulation frequency (abscissa, Hz). Data shown are mean±SEM. After inotropic
stimulation with 0.1 p£mol/L isoprenaline, force of contraction declined following an increase in stimulation frequency in nonfailing myocardium.
coplasmic Ca2+ handling, the biphasic Ca2+ transient
reported in failing human myocardium becomes
monophasic.4 The second signal L2 was observed only in
myopathic tissue. Because L2 was completely antagonized only by a combination of ryanodine plus verapamil, it has been suggested that the second component
of the Ca21 transient reflects dysfunction of the sarcoplasmic reticulum and the sarcolemmal membrane.16
Furthermore, myopathic muscle preparations exerted
similar responses to postextrasystolic potentiation as
has been observed in control muscle after exposure to
isoprenaline.7 The phospholamban-mediated Ca 2+ uptake26 in sarcoplasmic reticulum can be stimulated in
failing tissue as the effect of the cAMP-dependent
protein kinase on phospholamban phosphorylation and
Ca2+ uptake has been reported to be similar in nonfailing and failing myocardium.27 Moreover, the lusitropic
response was closely related to the phosphorylation of
phospholamban, whereas the cAMP-dependent inotropic response was directly related to the phosphorylation
of Ca21 channels in guinea pig atria.28 In addition,
lusitropy and phospholamban phosphorylation occurred at lower cAMP levels than positive inotropic
responses and Ca21 channel phosphorylation.28 Consis-
2274
Circulation Vol 88, No 5, Part 1 November 1993
HUMAN PAPILLARY MUSCLE STRIPS
NONFAILING
z
HUMAN PAPILLARY MUSCLE STRIPS
E
E
*t3
4
3
9
I
8
'a2
2
01
1
o Drug free
* 0.1 pmoOl BDF 9148 + 0.01 Pmol/l Ouabain
a
a
0.5
1.0
1.5
2.5
2.0
0.1
3.0
3
12
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
A Drugfree
A 0.1 pmoVI BDF 9148 + 0.01
pmoOl Ouabain
0
1.0
1.5
NYHA IV + 0.1 pmoif BDF 9148 + 0.01 pmoW Ouabain
1.0
1.5
2.0
2.5
3.0
Frequency (Hz)
HUMAN PAPILLARY MUSCLE STRIPS
0.5
Nonfailing
&
0.5
Frequency (Hz)
1
a
2.0
2.5
3.0
Frequency (Hz)
FIG 6. Plots of force-frequency relationship under basal
condition and after stimulation with BDF 9148 (0.1
,umol/L) plus ouabain (0.01 umol/L) in isolated electrically
driven papillary muscle strips from nonfailing (top) and
terminally failing (bottom) myocardium. The number of
strips studied was 14 in the failing and 4 in the nonfailing
group. Force of contraction with as well as without
pretreatment is given in Table 1. The ordinate gives force
of contraction in mN relative to stimulation frequency
(abscissa, Hz). Data shown are mean±95% confidence
limit. Stimulation with BDF 9148 and ouabain restored the
force-frequency relationship in NYHA class IV.
tently, in the presence of low concentrations of isoprenaline, -T increased more in relation to developed force
of contraction at higher frequency of stimulation. However, in isolated myocytes from myopathic human
hearts, cAMP did not significantly affect the alterations
in Ca2' handling observed.14 As in myopathic cells
diastolic intracellular Ca2' is already augmented,14 a
further increase by cAMP-dependent or -independent
positive inotropic agents may be detrimental. From
these findings, it can be suggested that only moderate
stimulation of cAMP is effective in improving myocardial function by facilitating diastolic Ca2' sequestration
by cAMP-dependent phosphorylation of phospholamban. However, higher concentrations of cAMP decrease
the force-frequency relationship5 in the failing but also
in nonfailing myocardium, possibly by producing cytosolic Ca2+ overload. Therefore, in human heart failure
in vivo, the enhanced endogenous catecholamine levels
could impair myocardial function by a further depression of the already inverse force-frequency relationship
due to an enhanced diastolic Ca2' load.
Effect of Elevation of Intracellular Na+
The combination of ouabain plus BDF 9148 was
effective to restore the positive force-frequency relationship in failing human myocardium due to dilated
cardiomyopathy. Following an increase in frequency of
FIG 7. Plot of force-frequency relationship after stimulation with BDF 9148 (0.1 ,umol/L) plus ouabain (0.01
,gmol/L) in isolated electrically driven papillary muscle
strips from nonfailing and terminally failing myocardium.
The number of strips studied was 14 in the failing and 4
in the nonfailing group. Force of contraction is given in
Table 1. The ordinate gives force of contraction in mN
relative to stimulation frequency (in Hz). Data shown are
mean±95% confidence limit. After stimulation with BDF
9148 and ouabain there was no statistically significant
difference between groups. (Please see also "Statistical
Analysis.")
stimulation, +T and -T increased, whereas TPT and
T1/2T decreased in failing myocardium. In nonfailing
tissue, force of contraction increased following an increase in stimulation rate. This "positive treppe" phenomenon was not changed in the presence of the
combination of BDF 9148 and ouabain in nonfailing
myocardium. There was no statistically significant difference between nonfailing and failing myocardium in
the presence of BDF 9148 plus ouabain. Cardiac glycosides enhance intracellular Na+, possibly via blockade of
the membrane-bound Na+ ,K+-ATPase.17 In addition,
the Na+ channel activator BDF 9148 increases intracellular Na+ that activates the Na+/Ca2+ exchange mechanism to increase intracellular Ca 2+.8 In contrast to
fl-adrenergic stimulation, both compounds remain effective in increasing force of contraction in failing
human myocardium.'19
In muscle strip preparations from a patient with
hypertrophic cardiomyopathy, 0.4 ,umol/L acetylstrophanthidin exacerbated the decrease in tension development that occurred at higher frequencies of stimulation in high extracellular Ca21 concentrations.29 This
may be due to a Ca2+ overload induced by the high
concentration of the cardiac glycosides. However, in the
present study, when force of contraction was stimulated
only marginally by ouabain in the presence of BDF
9148, the "treppe phenomenon" was positive.
Prestimulation with BDF 9148 has been reported to
enhance sensitivity to ouabain in human myocardium.19
Consistently, the combination of BDF 9148 plus ouabain
was more potent in restoring the force-frequency relationship in NYHA class IV compared with ouabain alone.5
Both compounds activate membrane-bound Na+/Ca21
exchange mechanisms and thereby influence the sarcolemmal Ca2+ transient and intracellular Ca2' homeostasis.18 As in nonfailing and failing human myocardium
the force-frequency relationship became positive in the
presence of low concentrations of ouabain and BDF 9148,
the Na+/Ca2+ exchanger may be effective in NYHA class
Schwinger et al Human Myocardium and Force-Frequency Relationship
1
E
2
HUMAN PAPILLARY MUSCLE STRIPS
,
1.s
c
10
NYHA IV
|
Q
M
1. 1
2275
HUMAN PAPILLARY MUSCLE STRIPS
NYHA IV
9
E 8
Drug free
Mmobl BDF 9148 + 0.01 moAOuabain
7
0.1
'a Drugfr*e
A 3.2 mmo Ca 2'
.5
4
ID
03
.5
.0
02
4
U1
0 '-
05-1.0
1.01.5
1.5-2.0
2.0-2.5
2.5.3.0
0.5
1.0
Change in frequency (Hz)
1.5
2.0
2.5
3.0
Frequency (Hz)
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
FIG 8. Bar graph of change in force of contraction
(ordinate, AmN) plotted as a function of change in
frequency of stimulation (abscissa) in electrically driven
papillary muscle strips from terminally failing myocardium
with as well as without pretreatment with BDF 9148 and
ouabain. The number of strips studied was 58 in the
control and 14 in the BDF 9148 plus ouabain group. The
figure illustrates the change in force of contraction at
various changes in frequency of stimulation. (Please see
also "Statistical Analysis.") Data shown are mean±95%
confidence limit.
10
HUMAN PAPILLARY MUSCLE STRIPS
NYHA IV
9
E
C
8
7
0
A Dug free
A 6.2 m~ol Ca 2-
c
CD
3
2
1
0
0.5
1.0
1.5
2.0
2.5
3.0
Frequency (Hz)
IV in influencing Ca2' handling. Pretreatment with low
concentrations of ouabain plus BDF 9148 and isoprenaline influenced the force-frequency relationship, similarly
indicating that the underlying mechanism responsible for
improvement of the force-frequency relationship may represent not specific cAMP-dependent mechanisms rather
than other effects on intracellular Ca2' handling. Possible
mechanisms are related to intracellular Na' or Ca2'
concentrations, Na' or Ca2+ currents, sarcoplasmic reticulum function, altered activity of the Na+/Ca2` exchange
mechanism, or differences in Na+,K+-ATPase function;
eg, in myopathic tissue, significantly higher resting and
end-diastolic Ca2' levels were measured. Since the positive force-frequency relationship has been suggested to
involve the Na' influx,25 it is not unreasonable to speculate
that in failing heart muscle the availability of the intracellular Na' is altered. This is supported by the finding that
increasing intracellular Na+ by BDF 9148 and ouabain
restores this dysfunction in the failing heart.
Effect of Ca 2+
Elevation of extracellular Ca 2+ was accompanied by a
negative force-frequency relationship in failing
human myocardial tissue. In simultaneous measurements with the Ca2+ indicator aequorin, the peak amplitude of the Ca21 transient and the resting intracellular Ca 2+ concentration increased in parallel with
increasing stimulation frequencies.4 Therefore, the mechanical deterioration during a frequency increase is not
due to a reduced availability of the cytosolic Ca2+ but
rather a diminished Ca2' reuptake from the cytosol.
Hence, pronounced elevation of intracellular Ca2+ will
aggravate the negative force-frequency relationship.
Following interventions that excessively increase intracellular Ca2 , such as high extracellular Ca2 an increase in stimulation frequency in human muscle strip
preparations causes an abbreviation of action potential
duration (APD) accompanied by a decreased augmentation of tension.4 In addition, at higher stimulation
rates, the Ca2' sensitivity of myofilaments in myopathic
more
,
FIG 9. Plots of force-frequency relationship under basal
condition and after inotropic stimulation with Ca2l (3.2
mmol/L) (top) or Ca2l (6.2 mmol/L) (bottom) in isolated
electrically driven papillary muscle strips from terminally
failing myocardium. The number of strips studied was 6
and 8 in the 3.2 mmol/L Ca2+ and 6.2 mmol/L Ca2+
conditions. Basal force of contraction was 6.1±1.9 and
3.2+0.5 mN with as well as without 3.2 mmol/L Ca 2+ in
failing tissue. The corresponding values with 6.2 mmol/L
Ca2+ were 8.3±1.4 and 3.2±0.5 mN, respectively. The
ordinate gives force of contraction in mN relative to
stimulation frequency (abscissa, Hz). Data shown are
mean±SEM. Ca2+ enhanced the decline in force of
contraction at higher frequencies of stimulation.
muscle decreases.29 These findings indicate that the
actual amount of Ca2+ in the cytoplasm rather than the
way Ca2+ was entering the cell appears to be a determinant of myocardial contractility. The present findings
demonstrate that minimal inotropy is not detrimental
but that greater inotropy with Ca2+ loading is disadvantageous. However, as terminally failing patients reveal
elevated catecholamine levels, one might argue that an
intracellular Ca2+ overload might exist.
Clinical Implications
As the frequency-dependent dysfunction of myopathic
human myocytes does not appear to be caused by a
decreased availability of [Ca2+1], inotropic compounds
that produce directly a pronounced increase of Ca24 have
been suggested to be of limited value.29 As diastole is
primarily shortened during increased heart rates, a slow
heart rate would provide sufficient time to refill the
sarcoplasmic reticulum with Ca2' even when the sarcoplasmic reticulum Ca2+-ATPase shows a reduced uptake
rate, thereby reducing diastolic Ca2+ load of the myocardial cell. Therefore, compounds that decrease heart
rate -but with no or only minor effects on contractility
could be beneficial. The sympathoinhibitory responses to
digitalis glycosides in heart failure patients were studied by
-
2276
Circulation Vol 88, No 5, Part 1 November 1993
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
Ferguson et al.30 They observed a significant decrease in
heart rate following administration of digitalis in patients
with heart failure. As cardiac glycosides in clinically relevant concentrations exert negative chronotropy in addition
to positive inotropic actions, the beneficial effects of
cardiac glycosides could at least in part be due to their
actions on the force-frequency relationship. However, the
value of decreasing heart rate must be weighed. In patients with terminal heart failure, a 20% increase in force
of contraction in parallel with lowered 02 consumption, ie,
decreasing heart rate, may enhance cardiac output above
critical levels.
The present study demonstrates that increasing intracellular Ca2 concentrations may have detrimental effects on inotropy. In addition, the intracellular sodium
concentration in failing myocardium could be altered.31
The gene expression of the Na+/Ca 2+ exchange in
patients with heart failure was observed to be enhanced
compared with nonfailing controls.32 In consequence,
changes in intracellular Na' may be more effective in
affecting myocardial force of contraction in failing than
in nonfailing tissue. Moreover, indirect evidence for
differences in intracellular Na+ handling in failing human myocardium was also raised.19 Therefore, the
observed effects of agents increasing the intracellular
Na' suggest a novel pathophysiological alteration of the
Na' homeostasis in failing heart that is sensitive to
pharmacologic interventions. Even though increasing
[Ca 2+]i in failing heart cells may be detrimental, increasing [Na+]i may be beneficial through a mechanism
independent of an increase in [Ca2]i.
Acknowledgments
Experimental work was supported by the Deutsche Forschungsgemeinschaft (D.F.G.). M.B. is supported by the Gerhard Hess program of the D.F.G. We thank Heidrun Villena
Hermoza for her excellent technical help.
References
1. Buckley NM, Penefsky ZJ, Litwak RS. Comparative forcefrequency relationship in human and other mammalian ventricular
myocardium. Pflugers Arch. 1972;332:259-270.
2. Feldman MD, Gwathmey JK, Phillips P, Schoen F, Morgan JP.
Reversal of the force-frequency-relationship in working myocardium from patients with endstage heart failure. J Appl Cardiol.
1988;3:273-283.
3. Mulieri LA, Hasenfuss G, Leavitt B, Allen PD, Alpert NR. Altered
myocardial force-frequency relation in human heart failure. Circulation. 1992;85:1743-1750.
4. Gwathmey JK, Slawsky MT, Hajjar RJ, Briggs GM, Morgan JP.
Role of intracellular calcium handling in force-interval relationships of human ventricular myocardium. J Clin Invest. 1990;85:
1599-1613.
5. Bohm M, La Rosee K, Schmidt U, Schulz C, Schwinger RHG,
Erdmann E. Force-frequency relationship and inotropic stimulation in the nonfailing and failing human myocardium: implications for the medical treatment of heart failure. Clin Invest.
1992;70:421-425.
6. Schwinger RHG, Bohm M, Erdmann E. Inotropic and lusitropic
dysfunction in myocardium from patients with dilated cardiomyopathy. Am Heart J. 1992;123:116-128.
7. Phillips PJ, Gwathmey JK, Feldman MD, Schoen FJ, Grossman W,
Morgan JP. Post-extrasystolic potentiation and the force-frequency
relationship: differential augmentation of myocardial contractility
in working myocardium from patients with end-stage heart failure.
J Mol Cell Cardiol. 1990;22:99-110.
8. Feldman MD, Alderman JD, Aroesty JM, Royal HD, Ferguson JJ,
Owen RM, Grossman W, McKay RG. Depression of systolic and
diastolic myocardial reserve during atrial pacing tachycardia in
patients with dilated cardiomyopathy. J Clin Invest. 1988;82:
1661-1669.
9. Bristow MR, Ginsburg R, Minobe W, Cubiciotti RS, Sageman WS,
Lurie K, Billingham ME, Harrison DC, Stinson EB. Decreased
catecholamine sensitivity and beta-adrenergic-receptor density in
failing human hearts. N Engl J Med. 1982;307:205-211.
10. Feldman AM, Cates AE, Veazey WB, Hershberger RE, Bristow
MR, Raughman KL, Baumgartner WA, Van Dop C. Increase of
the 40 000-mol wt pertussis toxin substrate (G protein) in the
failing human heart. J Clin Invest. 1988;82:189-197.
11. Bohm M, Gierschik P, Jakobs KH, Pieske B, Schnabel P, Ungerer
M, Erdmann E. Increase of Gia in human hearts with dilated but
not ischemic cardiomyopathy. Circulation. 1990;82:1249-1265.
12. Danielsen W, von der Leyen H, Meyer W, Neumann J, Schmitz W,
Scholz H, Starbatty J, Stein B, Doring V, Kalmar P. Basal and
isoprenaline-stimulated cAMP content in failing versus nonfailing
human cardiac preparation. J Cardiovasc Pharmacol. 1989;14:171-173.
13. Feldman MD, Copelas L, Gwathmey JK, Phillips P, Warren SE,
Schoen FJ, Grossman W, Morgan JP. Deficient production of
cyclic AMP: pharmacologic evidence of an important cause of
contractile dysfunction in patients with end-stage heart failure.
Circulation. 1987;75:331-339.
14. Beuckelmann DJ, Nabauer M, Erdmann E. Intracellular calcium
handling in isolated ventricular myocytes from patients with
terminal heart failure. Circulation. 1992;85:1046-1055.
15. Morgan JP. Abnormal intracellular modulation of calcium as a
major cause of cardiac contractile dysfunction. N Engl J Med.
1991;325:625-632.
16. Gwathmey JK, Copelas L, Mackkinnon R, Schoen FJ, Feldman
MD, Grossman W, Morgan JP. Abnormal intracellular calcium
handling in myocardium from patients with end-stage heart failure.
Circ Res. 1987;61:70-76.
17. Akera T, Brody TM. The role of Na+,K+-ATPase in the inotropic
action of digitalis. Pharmacol Rev. 1978;29:187-220.
18. Ravens U, Wettwer E. Modulation of sodium/calcium exchange: a
hypothetical positive inotropic mechanism. J Cardiovasc
Pharmacol. 1988;12:726-732.
19. Schwinger RHG, Bohm M, La Rosee K, Schmidt U, Schulz C,
Erdmann E. Na+-channel activators increase cardiac glycoside sensitivity in failing human myocardium. J Cardiovasc Pharmacol.
1992;19:554-561.
20. Herzig S, Lilienthal E, Mohr K. The positive inotropic drug DPI
201-106, BDF 9148, and veratridine increase ouabain toxicity and
'H-ouabain binding in guinea pig heart. J Cardiovasc Pharmacol.
1991;18:182-189.
21. Paradise NF, Schmitter JL, Surmitis JM. Criteria for adequate
oxygenation of isometric kitten papillary muscle. Am J Physiol.
1981;241:H348-H353.
22. Wallenstein S, Zucker CL, Fleiss JL. Some statistical methods
useful in circulation research. Circ Res. 1980;47:1-9.
23. SAS/Stat User Guide, version 6. Cary, NC: SAS Institute Inc, 1989.
24. Ginsburg R, Bristow MR, Billingham ME, Stinson EB, Schroeder
JS, Harrison DC. Study of normal and failing isolated human
heart: decreased response of failing heart to isoproterenol. Am
Heart J. 1983;106:535-540.
25. Framton JE, Harrison SM, Boyett MR, Orchard CH. Ca2` and
Na+ in rat myocytes showing different force-frequency relationships. Am J Physiol. 1991;261(Cell Physiol 30):C739-C750.
26. Davis BA, Edes J, Gupta RC, Young EF, Kim HW, Steenart NAB,
Szymanska G, Kranias EG. The role of phospholamban in the
regulation of calcium transport by cardiac sarcoplasmic reticulum.
Mol Cell Biochem. 1900;99:83-88.
27. Movsesian MA, Colyer J, Wang JH, Krall J. Phospholamban
mediated stimulation of Ca 2+ uptake in sarcoplasmic reticulum
from normal and failing hearts. J Clin Invest. 1990;85:1698-1702.
28. Kenakin TP, Ambrose JR, Irving PE. The relative efficiency of
beta adrenoceptor coupling to myocardial inotropy and diastolic
relaxation: organ selective treatment for diastolic dysfunction.
J Pharmacol Exp Ther. 1991;257:1189-1197.
29. Gwathmey JK, Warren SE, Briggs GM, Copelas L, Feldman MD,
Phillips PJ, Callahan M, Schoen FJ, Grossman W, Morgan JP.
Diastolic dysfunction in hypertrophic cardiomyopathy. J Clin
Invest. 1991;87:1023-1031.
30. Ferguson DW, Berg WJ, Sanders JS, Roach PJ, Kempf JS, Kienzle
MG. Sympathoinhibitory responses to digitalis glycosides in heart
failure patients. Circulation. 1989;80:65-77.
31. Forbat LN, Fry CH. The physiology of human hypertrophic myocardium and impaired contractility. Br Heart J. 1991;64P.
32. Reinecke H, Studer R, Philipson KD, Bilger J, Eschenhagen T,
Bohm M, Just H-J, Holtz J, Drexler H. Myocardial gene expression
of Na+/Ca 2+ exchanger and sarcoplasmic reticulum Ca 2+-ATPase
in human heart failure. Circulation. 1992;86(suppl I):I-860.
Effect of inotropic stimulation on the negative force-frequency relationship in the failing human
heart.
R H Schwinger, M Böhm, J Müller-Ehmsen, R Uhlmann, U Schmidt, A Stäblein, P Uberfuhr, E
Kreuzer, B Reichart and H J Eissner
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
Circulation. 1993;88:2267-2276
doi: 10.1161/01.CIR.88.5.2267
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1993 American Heart Association, Inc. All rights reserved.
Print ISSN: 0009-7322. Online ISSN: 1524-4539
The online version of this article, along with updated information and services, is located on the
World Wide Web at:
http://circ.ahajournals.org/content/88/5/2267
Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in
Circulation 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 is online at:
http://circ.ahajournals.org//subscriptions/