Abstract Tumor necrosis factor-α (TNF-α) likely plays a role in the pathophysiology of myocardial depression observed in septic shock. To evaluate the hemodynamic effects of TNF-α in vivo while eliminating the influence of altered sympathetic tone, eight conscious chronically instrumented dogs were studied after pretreatment with propranolol (2 mg/kg) and atropine (2 mg). Using three sets of piezoelectric crystals to measure left ventricular (LV) volume and LV manometers to measure pressure, we determined load-independent parameters of LV systolic performance before, during, and after infusion of recombinant human TNF-α (rhTNF-α, 40 μg/kg for 1 hour). Plasma was analyzed for epinephrine and norepinephrine. Between 1 and 7 hours of exposure, rhTNF-α induced significant increases in circulating catecholamines. Norepinephrine rose from 268.6±47.2 to 426.2±87.0 pg/mL (P<.05) at 1 hour and peaked at 921.2±156.8 pg/mL (P<.001) at 4 hours after initiating rhTNF-α treatment. Similarly, epinephrine increased from 130.2±30.9 to 884.5±210.2 pg/mL (P<.05) at 1 hour and peaked at 3195.3±476 pg/mL (P<.001) at 4 hours. Before the surge of circulating catecholamines and despite complete β-adrenergic blockade, rhTNF-α induced a 7% to 40% increase in LV contractile performance during the 60-minute infusion. After this initial positive inotropic effect, rhTNF-α treatment led to precipitous systolic dysfunction between 2 and 7 hours of exposure; this myocardial depressant effect persisted at 25 hours. LV systolic performance declined to 19% to 35% of baseline values, depending on the specific contractile parameter evaluated. We conclude that rhTNF-α affects LV systolic function in a time-dependent biphasic manner. Increases in circulating catecholamines after rhTNF-α infusion cannot account for the early improvement in LV systolic performance.
The specific mechanisms by which sepsis leads to hemodynamic disturbance and organ failure are not understood, although substantial evidence points to the role of TNF-α, a pleiotropic cytokine.1 Infusions of rhTNF-α in humans2 and animals3 4 5 have produced fever, hypotension, metabolic acidosis, hemoconcentration, capillary leak, and even death. Moreover, baboons pretreated with neutralizing monoclonal anti–TNF-α antibody fragments have been afforded complete protection from the hemodynamic collapse seen in endotoxic shock.6 More recently, TNF-α has been shown to play an adverse role in acute hypovolemic hemorrhagic shock, perhaps as a consequence of vascular hyporeactivity to α-adrenergic stimulation.7
In addition to its vasodilating effect, TNF-α appears to induce reversible myocardial dysfunction. Earlier studies have revealed that sepsis is associated with LV contractile impairment,8 9 attributable to a circulating myocardial depressant substance.10 Humans with septic shock have elevated TNF-α levels,11 and volunteers challenged with endotoxin develop increases in circulating TNF-α followed by LV dilation and a reduced ejection fraction.12 13 In vitro studies using isolated feline LV and cardiomyocytes14 and Syrian hamster papillary muscles15 have confirmed that TNF-α exerts a transient myocardial depressant effect, which occurs within minutes. Recent investigations have delineated the time course and dose dependence of rhTNF-α–induced myocardial dysfunction in conscious autonomically intact dogs.16 17 Unlike the in vitro studies, which have characterized an immediate negative inotropic influence, Pagani et al16 did not observe deterioration of myocardial performance until 24 hours after rhTNF-α treatment. In another canine study, however, LV ejection fraction was noted to initially decline 2 hours after rhTNF-α.17 Neither canine study has addressed potential TNF-α effects on the myocardium within the first 2 hours of exposure or the potentially confounding influences of altered sympathetic tone in the face of TNF-α–mediated vasodilation.
The objective of the present study was to define the kinetics of TNF-α–induced myocardial depression in vivo while neutralizing the changes that might occur in endogenous sympathetic tone. Accordingly, we studied the hemodynamic effects of rhTNF-α in conscious chronically instrumented dogs pretreated with a combination of propranolol and atropine. Our results will demonstrate that rhTNF-α induces a biphasic myocardial response, characterized by an early increase in LV contractility, followed by precipitous and sustained myodepression.
Materials and Methods
All animal studies were performed in accordance with the “Guide for Care and Use of Laboratory Animals” (Department of Health and Human Services publication No. [NIH] 85-23, revised 1985); eight adult mongrel dogs (22 to 30 kg) of either sex were used. The surgical preparation has been described in detail previously.18 In brief, after intravenous sedation with 2.5% sodium pentothal (6 to 10 mL) and acepromazine (0.25 mg/kg), the animals were intubated and anesthetized with 1% to 2% isofluorane. Under sterile conditions, a left thoracotomy was performed. Three sets of piezoelectric crystals were implanted in the endocardium of the LV, oriented orthogonally, to allow for continuous assessment of the DAP, DSL, and DLA. A micromanometer-tipped catheter (Konigsberg Instruments) and a fluid-filled polyvinyl catheter (1.1-mm internal diameter) were placed through the LV apex and held in place by a purse-string suture. A second fluid-filled catheter was positioned in the left atrium for infusion of drugs and saline; a third fluid-filled catheter was inserted into the aortic arch to measure arterial pressure and to collect blood samples. Pacing electrodes were sutured to the left atrium, and balloon occluder cuffs were positioned around the inferior vena cava to permit alteration of LV loading during the experiments. All leads, catheters, and occluders were exteriorized dorsal to the thoracotomy incision, and the chest was closed. After surgery, the animals received trimethoprim/sulfadiazine (960 mg daily for 7 days).
The dogs were studied after full recovery from surgery, a period of at least 10 days, during which time they were trained to lie quietly in a sling. Data were collected with the animals awake and unsedated. The LV catheter was connected to a Statham P23 dB pressure gauge calibrated against a mercury manometer. The signal from the manometer-tipped catheter was matched with the fluid-filled catheter in the LV apex. Lead II of the surface ECG was recorded. LV dimensions were obtained from the three sets of piezoelectric crystals coupled to a sonomicrometer (Triton Technology).
Analog recordings were made on an eight-channel forced-ink oscillograph (Beckman Instruments) at a paper speed of 25 mm/s. The following variables were measured: PLV, the first derivative of PLV with respect to time (dP/dt), ECG, the three diameters, and aortic pressure. These variables were simultaneously converted to digital form at a rate of 500 Hz and stored on floppy disks. Digital data were recorded for 12-second periods under control conditions and after caval occlusions.
Whole Animal Studies
After surgery, the dogs’ temperatures, body weights, and overall conditions were monitored daily. Systemic infection was ruled out with blood cultures. The studies were conducted after pretreatment with propranolol (2 mg/kg) and atropine (2 mg). To ensure the adequacy of β-adrenergic blockade, we evaluated the hemodynamic performance and heart rate in five dogs on an hourly basis before and after brief infusions of dobutamine at 5 μg/kg per minute, a dose that typically increases LV contractility ≈50% to 75% in this model. After treatment with propranolol and atropine as described above, dobutamine had no effect on LV systolic function and heart rate, a finding that persisted for 7 hours.
We proceeded to study the hemodynamic performance in eight dogs before and after rhTNF-α. Approximately 10 minutes after the infusion of propranolol and atropine, blood was obtained for catecholamine analysis, followed by acquisition of baseline hemodynamic data. After steady state recordings were made, vena caval occlusions were performed to define LV function over a range of loading conditions. Immediately after the recording period, the vena caval occlusion was released. All studies were performed at a paced rate of 160 bpm.
After acquisition of baseline data, the animals received 40 μg/kg of rhTNF-α (lot EB6011) kindly supplied by Knoll Pharmaceutical, Inc. This dose was selected because it has been shown to impact on LV function in a previously published study of intact animals. Specific activity was 1×107 U/mg protein, and the lipopolysaccharide content was <0.5 ng/mg protein (manufacturer’s data). Individual doses of active rhTNF-α were reconstituted in 20 mL of saline and administered over 1 hour into the left atrium via a calibrated infusion pump. Before rhTNF-α infusion, the tubing and syringes were treated with 3 mL of canine plasma. Hemodynamic recordings before and during caval occlusions were obtained 5, 15, 30, and 60 minutes into the rhTNF-α infusion as well as 2, 3, 4, 7, and 25 hours after starting the rhTNF-α infusion. Dogs received a repeated dose of propranolol (2 mg/kg) and atropine (2 mg) before the 25-hour study. Two milliliters of blood was obtained at each time point, after propranolol/atropine infusion and before vena caval occlusions, for catecholamine analysis.
Of the eight dogs that underwent the rhTNF-α protocol after pretreatment with propranolol/atropine, six dogs survived the study. One of the survivors developed pulsus alternans with inferior vena caval occlusion at 4 hours, precluding the ability to evaluate contractility 4,7, and 25 hours after rhTNF-α exposure. Two dogs developed status epilepticus and died ≈5 hours into the study. The hemodynamic data from the nonsurvivors were included in the analysis.
At the end of the studies, the animals were killed by lethal injection of pentobarbital sodium and potassium chloride. The hearts were excised and dissected to confirm proper positioning of the instruments and the absence of heart worms.
Plasma Catecholamine Measurement
Plasma samples were obtained from blood samples collected into chilled syringes containing 0.025 mL of ethylene glycol tetraacetic acid (95 mg/mL) and reduced glutathione (60 mg/mL) per 1 mL blood.
Catecholamine determinations were carried out by following the technique of Peuler and Johnson.19 Endogenous catecholamines were converted to radiolabeled O-methylcatecholamine derivatives by incubating plasma samples with catechol-O-methyltransferase isolated from rat liver and a tritiated methyl group donor, S-adenosyl-l-methionine. The 3H derivatives were then extracted and separated by thin-layer chromatography. Zones containing [3H]metanephrine and [3H]normetanephrine were scraped into separate scintillation vials and converted to [3H]vanillin by oxidation with sodium periodate. Tritium (in counts per minute) was measured by the addition of a toluene-based scintillation fluid and counted with a window setting appropriate for tritium. This method has a minimum sensitivity of 20 pg/mL, with an interassay coefficient of variation of 6% and a between-assay coefficient of variation of 10%.
The digitized data were analyzed by using software developed in our laboratory. Pressure and diameter data were analyzed without the use of digital filters. VLV was calculated from the three orthogonal dimensions by using the following equation:
End diastole was defined as the time of the peak of the QRS complex of the surface ECG. Under control conditions, end systole was defined as the peak ratio of PLV to VLV23 ; for caval occlusion data, end systole was defined by using the iterative approach of Kono et al.24 dP/dt was calculated by using a running five-point Lagrangian fit of the instantaneous PLV data. For each dog, beats were chosen from the caval occlusion runs that had a common Ved to allow comparison of dP/dtmax independent of Ved. SW was calculated as the integral of PLV and VLV over each cardiac cycle as described by the following equation:
The period of isovolumic relaxation was defined as occurring between the time of peak negative dP/dt and the time when pressure fell to 5 mm Hg above the end-diastolic pressure for that beat. The time constant of isovolumic relaxation was determined by nonlinear regression analysis of the pressure and time data during isovolumic relaxation by using a monoexponential function of the following form:
where P0 was an estimate of the pressure at peak negative dP/dt, t was the time (in milliseconds), τ was the time constant of LV relaxation, and Pb was the floating pressure asymptote as t approached infinity. To solve for τ, we used a computer algorithm based on the method described by Hartley.25 For all of these parameters, the values for 20 to 25 consecutive beats, spanning two to three respiratory cycles, were averaged to yield a single result.
The slope and volume intercepts of the Pes-Ves relation,26 the SW-EDV relation,27 and thed P/dtmax-EDV relation28 were each determined by using a linear least-squares algorithm. For the Pes-Ves relation, end-systolic data were fit to the following equation:
where Ees was the slope of the relation and V0 was its volume-axis intercept. To evaluate the position of the relation in the physiological pressure range, VLV at Pes of 100 mm Hg was calculated and termed V100. For the SW-EDV relation, the data were fit to the following equation:
where Mw was the slope of the relation and Vw was its volume-axis intercept. For the dP/dtmax-EDV relation, the data were fit to the following equation:
where dE/dtmax was the slope of the relation and EDV0 was its volume-axis intercept. For analysis of these constructs, only caval occlusions that caused a reduction in Pes of at least 20 mm Hg were accepted.
Data are presented as mean±1 SEM. Measurements over various time points were compared against the corresponding pre–rhTNF-α value to determine their statistical significance. In these intragroup comparisons, an ANOVA of repeated measurements, based on the least-squares means to correct for missing values, was performed. In addition, certain values (Ees, Mw, dE/dtmax, dP/dtmax at a common Ved, and V100) were expressed as ratios (parameter at time n/parameter at time 0) and then compared versus 1 in a t test. A value of P<.05 was considered significant.
Effect of rhTNF-α on Circulating Norepinephrine and Epinephrine
Pretreatment with propranolol/atropine did not affect baseline levels of circulating catecholamines. Between 1 and 7 hours of exposure, rhTNF-α induced precipitous increases in circulating catecholamines (Fig 1⇓). After pretreatment with propranolol/atropine, norepinephrine rose from 268.6±47.2 to 426.2±87.0 pg/mL (P<.05) at completion of the 1-hour rhTNF-α infusion, peaking at 921.2±156.8 pg/mL (P<.001) at 4 hours. Similarly, epinephrine increased from 130.2±30.9 to 884.5±210.2 pg/mL (P<.05) at 1 hour and peaked at 3195.3±476.0 pg/mL (P<.001) at 4 hours. Catecholamine levels remained elevated at 7 hours but normalized by 25 hours.
Effect of rhTNF-α on LV Function in Propranolol/Atropine-Pretreated Dogs
LV systolic function significantly improved as early as 5 minutes into rhTNF-α infusion, persisting for the first hour following treatment when defined by Ees. Similar trends were observed for Mw and dE/dtmax (Table 1⇓). Normalization of contractile parameters to respective baseline values revealed additional significant increases in systolic performance, especially during the first 60 minutes of rhTNF-α exposure: Ees (18% to 40% increase during the first 120 minutes), Mw (3% to 7% increase over the first 60 minutes), and dE/dtmax (15% to 24% increase during the first 60 minutes). rhTNF-α also induced an increase in dP/dtmax when evaluated at steady state (Table 2⇓) as well as at a common Ved (peak value, 109.1±3.4% of baseline at 15 minutes; Fig 2⇓) during the initial 30 minutes of infusion.
Early enhanced LV systolic function was accompanied by a statistically significant 6% to 8% decline in V100 (Fig 3⇓) and by decreases in τ (Table 2⇑). This reduction in τ occurred despite increases in afterload. Pes increased as early as 5 minutes into rhTNF-α infusion, persisting up to 2 hours after infusion (P<.05 at 30 minutes and 1 hour after infusion). This initial increase in Pes was likely secondary to an rhTNF-α–induced surge in catecholamines, resulting in vascular α-receptor stimulation (Fig 1⇑). Neither Ped nor SW changed during the phase of improved LV contractility.
LV systolic performance eventually deteriorated after rhTNF-α infusion. Regardless of the contractile parameter evaluated, myocardial depression was evident at 25 hours (Table 1⇑, Fig 2⇑). The time of onset of LV systolic dysfunction differed, depending on which contractile parameter was assessed. dP/dtmax, measured at a common Ved, declined significantly as early as 2 hours, persisting to 25 hours (nadir, 65.1±5.9% of baseline value at 4 hours; Fig 2⇑). Although derived indexes of LV contractile function (Ees, Mw, and dE/dtmax) tended to show initial evidence of LV systolic impairment between 3 and 7 hours, significant reductions did not occur until 7 hours (dE/dtmax) and 25 hours (Ees and Mw) after onset of rhTNF-α (Table 1⇑). Between 4 and 25 hours, Mw decreased 9% to 19%, dE/dtmax decreased 14% to 29%, and dP/dtmax at a common Ved decreased 28% to 35% from baseline values. End-systolic elastance diminished 10% at 7 hours and 31% at 25 hours.
The onset of myocardial depression was accompanied by LV dilation, by reduced steady state dP/dtmax, by diminished SW, and shortly thereafter by slowed LV relaxation. These changes persisted at 25 hours (Table 2⇑). The increase in V100 mirrored the deterioration in dP/dtmax at a common Ved (16% to 31% increase between 3 and 25 hours, Fig 3⇑). The decrease in SW occurred as a consequence of decreases in stroke volume. Despite deterioration of LV contractile function, Ped did not change (Table 2⇑).
Our data show for the first time that rhTNF-α induces a biphasic myocardial response in conscious dogs, characterized by an early increase in contractility and a delayed sustained myodepression. Catecholamines are not responsible for the early positive inotropic effect of rhTNF-α; the initial enhancement of LV performance precedes a surge in epinephrine and norepinephrine and occurs despite complete β-adrenergic blockade. These data confirm the known negative inotropic effects of rhTNF-α while suggesting a complex multifactorial mechanism in the intact animal.
Our results differ from those of previous in vitro investigations. Studies performed using Syrian hamster papillary muscles and isolated intact feline LVs or cardiomyocytes have shown that TNF-α causes myocardial depression within 15 to 20 minutes of exposure.14 15 In juvenile or adult rat cardiomyocytes, TNF-α has been observed to have no immediate effect on baseline contractility.29 30 Contrary to these in vitro studies, we have found an increase in LV systolic performance during the first 60 to 120 minutes of rhTNF-α exposure in an in vivo model. Since our dogs are conscious and physiologically intact, preserved paracrine, endocrine, hematologic, and neurological influences may account for these differences.
The mechanism responsible for enhanced LV systolic function in the initial hours of rhTNF-α treatment is uncertain. However, we have shown that sympathoadrenal activation is not responsible for the initial positive inotropic influence of rhTNF-α. Given that our dogs were pretreated with propranolol at doses that provided complete β-adrenergic blockade, the precipitous increases in circulating catecholamines after rhTNF-α infusion cannot account for the early improvement in LV systolic performance. The relatively rapid improvement in LV systolic function after rhTNF-α treatment (as early as 5 to 15 minutes) suggests a direct influence on the myocardium or the release of a secondary mediator not requiring protein synthesis. Further studies will be required to define the mechanism of this effect.
LV systolic performance deteriorated 2 to 7 hours (depending on the contractile parameter evaluated) after completing rhTNF-α infusion, at the time when peak epinephrine levels were recorded. In this regard, our results are similar to those reported by Eichenholz et al.17 These investigators found a dose-dependent decrease in LV ejection fraction as early as 2 hours after completion of rhTNF-α treatment in autonomically intact conscious dogs, an effect that later became independent of dose and most pronounced at 8 hours. In our model, LV systolic performance was preserved at 2 hours after rhTNF-α infusion (with the exception of dP/dtmax at a common Ved) but began to deteriorate 1 hour later. These subtle differences may be attributed to the influence of loading conditions on LV ejection fraction; we avoided this problem by evaluating LV systolic function with relatively load-independent parameters of contractile performance.
Our data differ from those of Pagani et al,16 who did not find evidence of impaired myocardial performance in chronically instrumented dogs until 24 hours after rhTNF-α infusion. This difference may result from differences in instrumentation; we used three endocardial dimension signals to calculate LV volume, but they used a single epicardial dimension, an approach that is less accurate if changes occur in LV shape or wall thickness (secondary to edema).31 In addition, data in our study were acquired at a single paced heart rate, whereas in their study heart rate was allowed to vary. Since contractile performance is dependent on heart rate,20 coexistent tachycardia may have masked the negative effects of rhTNF-α. Furthermore, Pagani et al relied on the SW–end-diastolic dimension relation to assess LV contractility. This parameter may be relatively insensitive for detecting alterations in systolic function. Deviation of contractility from baseline values in our study was more prominently shown with Ees and dE/dtmax than with Mw, a measure similar to that used by Pagani et al. Finally, Pagani et al performed their investigations in autonomically intact dogs; a pronounced endogenous sympathoadrenal response may have obscured an earlier negative impact of rhTNF-α on LV systolic function.
rhTNF-α appears to affect diastolic as well as systolic LV performance. One such manifestation was a prolongation of τ, a finding that occurred in the absence of changes in loading conditions. Lengthening of τ was coupled to systolic dysfunction and likely reflects one aspect of a pattern of abnormal intracellular calcium handling that may be present in cardiac depression. In addition, LV dilation occurred without a change in end-diastolic pressure, suggesting rhTNF-α induced myocardial creep. Because we studied the dogs while they were conscious and spontaneously breathing, significant changes in intrathoracic pressure precluded a precise definition of the entire diastolic pressure-volume relation. Nonetheless, the finding of creep would confirm the prior results of Pagani et al,16 who made similar observations in intact dogs. Possible etiologies of myocardial creep include myocardial edema, disruption of the collagen supportive framework, and elongation of myocardial fibers.
Although the precise mechanism by which rhTNF-α leads to impaired contractile performance remains undefined, the temporal sequence we describe may provide helpful clues to its nature. As noted both in vitro14 15 and in vivo,3 14 15 16 17 the detrimental effects of TNF-α on myocardial function are fully reversible, similar to those seen with myocardial stunning, where oxygen-derived free radicals have been shown to play a major role.32 TNF-α is known to stimulate neutrophil migration33 and phagocytosis,34 adherence to endothelial cells35 and myocytes,36 and superoxide anion37 and hydrogen peroxide release.38 Thus, the delay in the onset of mechanical dysfunction observed in the present study may have been related to the time necessary for recruitment and activation of neutrophils in the coronary microcirculation.
Whether NO, a ubiquitous intracellular messenger involved in signal transduction,39 mediates TNF-α–induced myocardial depression is controversial. Myocytes are capable of expressing both constitutive and inducible isoforms of NO synthase.40 Although studies in isolated Syrian hamster papillary muscle have provided indirect evidence that TNF-α–induced contractile dysfunction results from enhanced activity of constitutive NO synthase,15 this finding has been refuted by subsequent investigations using feline cardiomyocytes.14 Our inability to demonstrate immediate contractile dysfunction would support the contention that TNF-α does not mediate its effects via constitutive NO synthase. Brady et al41 have proposed that the loss of contractility of cardiac myocytes in endotoxic shock is secondary to synthesis of an inducible NO synthase and subsequent NO generation and not activation of a constitutive NO synthase. The kinetics of TNF-α–induced mechanical dysfunction observed in the present study are compatible with this idea.
Other mechanisms may play a role in TNF-α–induced myocardial depression. Yokoyama et al14 suggested that the immediate negative inotropic effects of TNF-α observed in isolated feline LVs and cardiomyocytes result from alterations in intracellular calcium homeostasis, independent of the need for de novo protein synthesis, arachidonic acid metabolism, or NO synthesis. As with the study by Finkel et al,15 these in vitro studies have focused on mechanisms responsible for TNF-α–induced myocardial dysfunction in the first 5 to 20 minutes of exposure, an effect that we were unable to duplicate in vivo. Although Yokoyama et al discount the need for de novo protein synthesis to mediate rapid TNF-α impairment of cardiomyocyte contractility in vitro, protein synthesis may be necessary for the induction of profound myocardial dysfunction observed 4 hours after TNF-α exposure in vivo. Other potential causes of TNF-α–induced contractile depression include direct injury to myocardial fibers, disruption or rearrangement of the interstitial matrix, and formation of myocardial edema via capillary leakage. These effects may take hours to manifest. On the basis of previous studies, neither systemic metabolic abnormalities nor changes in coronary blood flow are likely to be responsible.16
The present study must be interpreted in light of possible limitations. We have assumed that the three relations used for assessment of LV performance are linear. Prior studies in our preparation have shown that although the Pes-Ves relation is nonlinear, the degree of nonlinearity is consistent over a broad range of contractile states; in the physiological range, the assumption of linearity does not introduce substantial error.42 Thus, we are confident that this assumption has not affected our results. To illustrate how the hearts behaved in the physiological range of pressures, we have shown data on V100, the Ves achieved when confronted by a Pes of 100 mm Hg. Although our data have shown that significant rightward shifts of these Pes-Ves relations at 100 mm Hg occurred consistently with depressed indexes of LV performance, leftward shifts of these relations were not always seen during periods of enhanced LV contractility as defined by Ees (V100 not always significantly decreased at each time point). These observations likely result from concomitant increases in the extrapolated x intercept for each relation. This pattern has previously been seen in our laboratory in the setting of contractile augmentation by the force-frequency effect.20
In conclusion, conscious dogs exhibit a biphasic myocardial response to a 1-hour infusion of rhTNF-α. Early positive inotropic effects occur even in the face of complete β-adrenergic blockade, ruling out a catecholamine-mediated phenomenon. Myocardial depression occurs between 2 and 7 hours (depending on the contractile parameter evaluated) after initiating rhTNF-α treatment. In addition to its effects on contractile function, rhTNF-α impairs LV diastolic relaxation and promotes LV myocardial dilation. TNF-α likely plays an integral role in myocardial depression observed in septic shock and may be involved in the pathophysiology of myocarditis,43 cardiac allograft rejection,44 and congestive heart failure.45 Additional studies need to be performed in order to precisely define the mechanisms responsible for the detrimental influence of TNF-α on myocardial function.
Selected Abbreviations and Acronyms
|τ||=||time constant of LV relaxation|
|DAP, DSL,||=||anterior-posterior, septal-lateral, and long-|
|axis diameters of the LV|
|dE/dtmax||=||slope of the dP/dtmax-EDV relation|
|Ees||=||slope of the Pes-Ves relation|
|EDV0||=||volume-axis intercept of the dP/dtmax-EDV relation|
|LV||=||left ventricle, left ventricular|
|Mw||=||slope of the SW-EDV relation|
|Ped||=||LV end-diastolic pressure|
|Pes||=||LV end-systolic pressure|
|rhTNF-α||=||recombinant human TNF-α|
|TNF-α||=||tumor necrosis factor-α|
|V0||=||volume-axis intercept of the Pes-Ves relation|
|V100||=||VLV at Pes of 100 mm Hg|
|Ved||=||LV end-diastolic volume|
|Ves||=||LV end-systolic volume|
|Vw||=||volume-axis intercept of the SW-EDV relation|
This study was supported in part by an institutional research grant and by an American Heart Association Grant-in-Aid (Dr Murray) and the Research Service of the Department of Veterans Affairs (Dr Freeman). The authors thank Danny Escobedo and Cindy Ramirez for technical assistance, Norma Garcia for processing the manuscript, Merardo Monzon for software development, Gabriela Helesic and Dr Robert E. Shade for catecholamine analysis, and Dr Cheng Yuan for statistical assistance. We also thank Knoll Pharmaceutical for supplying the rhTNF-α used in these studies.
- Received August 25, 1994.
- Accepted October 2, 1995.
- © 1996 American Heart Association, Inc.
Blick M, Sherwin SA, Rosenblum M, Gutterman J. Phase I study of recombinant tumor necrosis factor in cancer patients. Cancer Res. 1987;47:2986-2989.
Natanson CP, Eichenholz PW, Danner RL, Eichacker PQ, Hoffman WD, Kuo GC, Banks SM, MacVittie TJ, Parrillo JE. Endotoxin and tumor necrosis factor challenges in dogs simulate the cardiovascular profile of human septic shock. J Exp Med. 1989;169:823-832.
Kreil EA, Greene E, Fitzgibbon C, Robinson DR, Zapol WM. Effects of recombinant human tumor necrosis factor alpha, lymphotoxin, and Escherichia coli lipopolysaccharide on hemodynamics, lung microvascular permeability, and eicosanoid synthesis in anesthetized sheep. Circ Res. 1989;65:502-514.
Zingarelli B, Squadrito F, Altavilla D, Calapai G, DiRosa M, Caputi AP. Role of tumor necrosis factor-α in acute hypovolemic hemorrhagic shock in rats. Am J Physiol. 1994;266(Heart Circ Physiol 35):H1512-H1515.
Parker MM, Shelhamer JH, Bacharach SL, Green MV, Natanson C, Frederick TM, Damske BA, Parrillo JE. Profound but reversible myocardial depression in patients with septic shock. Am J Int Med. 1984;100:483-490.
Natanson C, Fink MP, Ballantyne HK, MacVittie TJ, Conklin JJ, Parrillo JE. Gram-negative bacteremia produces both severe systolic and diastolic cardiac dysfunction in a canine model that simulates human septic shock. J Clin Invest. 1986;78:259-270.
Parrillo JE, Burch C, Shelhamer JH, Parker MM, Natanson C, Schuette W. A circulating myocardial depressant substance in humans with septic shock. J Clin Invest. 1985;76:1539-1553.
Calandra T, Baumgartner JD, Grau MM, Wu MM, Lambert PH, Schellekens J, Verhoef J, Glauser MP, for the Swiss-Dutch J5 Immunoglobulin Study Group. Prognostic values of tumor necrosis factor/cachectin, interleukin-1, interferon-alpha, and interferon-gamma in the serum of patients with septic shock. J Infect Dis. 1990;161:982-987.
Yokoyama T, Vaca L, Rossen RD, Durante W, Hazarika P, Mann DL. Cellular basis for the negative inotropic effects of tumor necrosis factor-α in the adult mammalian heart. J Clin Invest. 1993;92:2303-2312.
Finkel MS, Oddis CV, Jacob TD, Watkins SC, Hattler BG, Simmons RL. Negative inotropic effects of cytokines on the heart mediated by nitric oxide. Science. 1992;257:387-389.
Pagani FD, Baker LS, Hsi C, Knox M, Fink MP, Visner MS. Left ventricular systolic and diastolic dysfunction after infusion of tumor necrosis factor-α in conscious dogs. J Clin Invest. 1992;90:389-398.
Eichenholz PW, Eichacker PQ, Hoffman WD, Banks SM, Parrillo JE, Danner RL, Natanson C. Tumor necrosis factor challenges in canines: patterns of cardiovascular dysfunction. Am J Physiol. 1992;263:H668-H675.
Sodums MT, Badke FR, Starling MR, Little WC, O’Rourke RA. Evaluation of left ventricular contractile performance utilizing end-systolic pressure-volume relations in conscious dogs. Circ Res. 1984;54:731-739.
Freeman GL, Little WC, O’Rourke RA. Influence of heart rate on left ventricular performance in conscious dogs. Circ Res. 1987;61:455-464.
Little WC, Park RC, Freeman GL. Effect of regional ischemia and ventricular pacing on LV dP/dtmax-end-diastolic volume relation. Am J Physiol. 1987;252(Heart Circ Physiol 21):H933-H940.
Freeman GL, Little WC, O’Rourke RA. The effect of vasoactive agents on the left ventricular end-systolic pressure-volume relation in closed-chest dogs. Circulation. 1986;74:1107-1113.
Kono A, Maughan WL, Sunagawa K, Hamilton K, Sagawa K, Weisfeldt ML. The use of left ventricular end-ejection pressure and peak pressure in the estimation of the end-systolic pressure-volume relation. Circulation. 1984;70:1057-1065.
Kass DA, Maughan WL. From ‘EMAX’ to pressure-volume relations: a broader view. Circulation. 1988;77:1203-1212.
Glower DD, Spratt JA, Snow ND, Kabas JS, Davis JW, Olsen CO, Tyson GS, Rankin JS. Linearity of the Frank-Starling relationship in the intact heart: the concept of preload recruitable stroke work. Circulation. 1985;71:994-1009.
Little WC. The left ventricular dP/dtmax–end-diastolic volume relation in closed chest dogs. Circ Res. 1985;56:808-815.
Gulick T, Chung MK, Pieper SJ, Lange LG, Schreiner GF. Interleukin-1 and tumor necrosis factor inhibit cardiac myocyte β-adrenergic responsiveness. Proc Natl Acad Sci U S A. 1989;86:6753-6757.
Balligand J-L, Ungureanu D, Kelly RA, Kobzik L, Pimental D, Michel T, Smith TW. Abnormal contractile function due to induction of nitric oxide synthesis in rat cardiac myocytes follows exposure to activated macrophage-conditioned medium. J Clin Invest. 1993;91:2314-2319.
Little WC, Freeman GL, O’Rourke RA. Simultaneous determination of left ventricular end-systolic pressure-volume and pressure-dimension relations in closed-chest dogs. Circulation. 1985;71:1301-1308.
Bolli R. Mechanism of myocardial ‘stunning.’ Circulation. 1990;82:723-738.
Figari IS, Mori NA, Palladino MA. Regulation of neutrophil migration and superoxide production by recombinant tumor necrosis factors -α and -β: comparison to recombinant interferon-γ and interleukin−1α. Blood. 1987;70:979-984.
Klebanoff SJ, Vadas MA, Harlan JM, Sparks LH, Gamble JR, Agosti JM, Waltersdorph AM. Stimulation of neutrophils by tumor necrosis factor. J Immunol. 1986;136:4220-4225.
Moser R, Schleiffenbaum B, Groscurth P, Fehr J. Interleukin-1 and tumor necrosis factor stimulate human vascular endothelial cells to promote transendothelial neutrophil passage. J Clin Invest. 1989;83:445-455.
Entman ML, Youker K, Shappell SB, Siegel C, Rothlein R, Dreyer WJ, Schmalstieg FC, Smith CW. Neutrophil adherence to isolated adult canine myocytes: evidence for a CD18-dependent mechanism. J Clin Invest. 1990;85:1497-1506.
Nathan CF. Neutrophil activation on biological surfaces: massive secretion of hydrogen peroxide in response to products of macrophages and lymphocytes. J Clin Invest. 1987;80:1550-1560.
Brady AJ, Poole-Wilson PA, Harding SE, Warren JB. Nitric oxide production within cardiac myocytes reduces their contractility in endotoxemia. Am J Physiol. 1992;263:H1963-H1966.
Little WC, Cheng C-P, Peterson T, Vinten-Johansen J. Response of the left ventricular end-systolic pressure-volume relation in conscious dogs to a wide range of contractile states. Circulation. 1988;78:736-745.
Smith SC, Allen PM. Neutralization of endogenous tumor necrosis factor ameliorates the severity of myosin-induced myocarditis. Circ Res. 1992;70:856-863.
Levine B, Kalman J, Mayer L, Fillit HM, Packer M. Elevated circulating levels of tumor necrosis factor in severe chronic heart failure. N Engl J Med. 1990;223:236-241.