Effects of epinephrine and amrinone on contractility and cyclic adenosine monophosphate generation of tumor necrosis factor alpha-exposed cardiac myocytes

MECHANISMS OF CARDIAC DYSFUNCTION IN SEPSIS

ABSTRACT

Studies in animal models of sepsis have elucidated an intricate network of signaling pathways that lead to the dysregulation of myocardial Ca 2+ handling and subsequently to a decrease in cardiac contractile force, in a sex- and model-dependent manner. After challenge with a lethal dose of LPS, male animals show a decrease in cellular Ca 2+ transients (ΔCa i ), with intact myofilament function, whereas female animals show myofilament dysfunction, with intact ΔCa i . Male mice challenged with a low, nonlethal dose of LPS also develop myofilament desensitization, with intact ΔCa i . In the cecal ligation and puncture (CLP) model, the causative mechanisms seem similar to those in the LPS model in male mice and are unknown in female subjects. ΔCa i decrease in male mice is primarily due to redox-dependent inhibition of sarco/endoplasmic reticulum Ca 2+ ATP-ase (SERCA). Reactive oxygen species (ROS) are overproduced by dysregulated mitochondria and the enzymes NADPH/NADH oxidase, cyclooxygenase, and xanthine oxidase. In addition to inhibiting SERCA, ROS amplify cardiomyocyte cytokine production and mitochondrial dysfunction, making the process self-propagating. In contrast, female animals may exhibit a natural redox resilience. Myofilament dysfunction is due to hyperphosphorylation of troponin I, troponin T cleavage by caspase-3, and overproduction of cGMP by NO-activated soluble guanylate cyclase. Depleted, dysfunctional, or uncoupled mitochondria likely synthesize less ATP in both sexes, but the role of energy deficit is not clear. NO produced by NO synthase (NOS)-3 and mitochondrial NOSs, protein kinases and phosphatases, the processes of autophagy and sarco/endoplasmic reticulum stress, and β-adrenergic insensitivity may also play currently uncertain roles.

Tumor Necrosis Factor-α in Heart Failure: an Updated Review

PURPOSE OF THE REVIEW

Proinflammatory cytokines are consistently elevated in congestive heart failure. In the current review, we provide an overview on the current understanding of how tumor necrosis factor-α (TNFα), a key proinflammatory cytokine, potentiates heart failure by overwhelming the anti-inflammatory responses disrupting the homeostasis.

RECENT FINDINGS

Studies have shown co-relationship between severity of heart failure and levels of the proinflammatory cytokine TNFα and one of its secondary mediators interleukin-6 (IL-6), suggesting their potential as biomarkers. Recent efforts have focused on understanding the mechanisms of how proinflammatory cytokines contribute towards cardiac dysfunction and failure. In addition, how unchecked proinflammatory cytokines and their cross-talk with sympathetic system overrides the anti-inflammatory response underlying failure. The review offers insights on how TNFα and IL-6 contribute to cardiac dysfunction and failure. Furthermore, this provides a forum to begin the discussion on the cross-talk between sympathetic drive and proinflammatory cytokines and its determinant role in deleterious outcomes.

Proinflammatory Cytokines Mediate GPCR Dysfunction

Proinflammatory reaction by the body occurs acutely in response to injury that is considered primarily beneficial. However, sustained proinflammatory cytokines observed with chronic pathologies such as metabolic syndrome, cancer, and arthritis are detrimental and in many cases is a major cardiovascular risk factor. Proinflammatory cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor α (TNFα) have long been implicated in cardiovascular risk and considered to be a major underlying cause for heart failure (HF). The failure of the anti-TNFα therapy for HF indicates our elusive understanding on the dichotomous role of proinflammatory cytokines on acutely beneficial effects versus long-term deleterious effects. Despite these well-described observations, less is known about the mechanistic underpinnings of proinflammatory cytokines especially TNFα in pathogenesis of HF. Increasing evidence suggests the existence of an active cross-talk between the TNFα receptor signaling and G-protein-coupled receptors such as β-adrenergic receptor (βAR). Given that βARs are the key regulators of cardiac function, the review will discuss the current state of understanding on the role of proinflammatory cytokine TNFα in regulating βAR function.

Infliximab attenuates early myocardial dysfunction after resuscitation in a swine cardiac arrest model

OBJECTIVE

Left ventricular dysfunction after successful cardiopulmonary resuscitation contributes to early death after resuscitation. Proinflammatory cytokines are known to decrease myocardial function, and tumor necrosis factor-alpha has been shown to increase after successful resuscitation. We hypothesized that blocking the effects of tumor necrosis factor-alpha with infliximab would prevent or minimize postresuscitation cardiac dysfunction.

DESIGN

Randomized, placebo-controlled comparative study.

SETTING

Large animal research laboratory.

SUBJECTS

Twenty-eight anesthetized and instrumented domestic male swine (Yorkshire and Yorkshire/Hampshire mix; weight, 35-45 kg).

INTERVENTIONS

Infusion of infliximab (5 mg/kg) or normal saline after resuscitation from ventricular fibrillation cardiac arrest.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic variables, indices of left ventricular function, and tumor necrosis factor-alpha were measured before and after 8 mins of cardiac arrest during the early postresuscitation period (3 hrs). Within 5 mins of restoration of spontaneous circulation, 14 animals received infliximab, 5 mg/kg, infused over 30 mins. Fourteen animals received an infusion of normal saline. Inotropes and vasopressors were not administered to either group after resuscitation. Tumor necrosis factor-alpha increased after restoration of circulation and remained elevated throughout the observation period. Differences between groups were not significant. Interleukin-1beta concentration did not change significantly during the observation period in either study group. Mean arterial pressure and stroke work were significantly greater in the infliximab group within 30 mins of resuscitation, and these differences were sustained throughout the 3-hr postresuscitation period. The effect of tumor necrosis factor-alpha blockade was evident only in animals with a significant increase (doubling) in plasma tumor necrosis factor-alpha at 30 mins after arrest.

CONCLUSION

Tumor necrosis factor-alpha plays a role in cardiac dysfunction after arrest and infliximab may attenuate or prevent postresuscitation myocardial dysfunction when administered immediately after resuscitation.

Nitric oxide-dependent and -independent mechanisms are involved in TNF-alpha -induced depression of cardiac myocyte contractility

Previous studies have demonstrated the presence of myocardial depression in clinical and experimental septic shock. This response is mediated, in part, through circulating TNF-alpha-induced, nitric oxide-dependent, depression of basal myocyte contractility. Other mechanisms of early myocardial dysfunction involving decreased response to adrenergic stimulation may exist. This study evaluated the presence and nitric oxide dependence of impaired adrenergic response to TNF-alpha in in vitro cardiac myocytes. The contraction of electrically paced neonatal rat cardiac myocytes in tissue culture was quantified using a closed-loop video tracking system. TNF-alpha induced depression of baseline contractility over the first 20 min of cardiac myocyte exposure. This effect was blocked by N-methyl-arginine (NMA), a nitric oxide synthase inhibitor, in all studies. Contractile and cAMP response to increasing concentrations of isoproterenol was deficient in cardiac myocytes exposed to TNF-alpha regardless of the presence of NMA. In contrast, increasing concentrations of forskolin (a direct stimulant of adenylate cyclase) and dibutyryl cAMP (a metabolically active membrane-soluble analog of cAMP) completely reversed TNF-alpha-mediated depression, though only in the presence of NMA. Forskolin-stimulated cAMP generation remained intact regardless of NMA. Increasing concentrations of exogenous calcium chloride, unlike other inotropic agents, corrected TNF-alpha-mediated defects of contractility independent of the presence of NMA. These data suggest that TNF-alpha exposure is associated with a second nitric oxide-independent but calcium-dependent early depressant mechanism that is manifested by reduced contractile and cAMP response to beta-adrenergic stimulation.

Steroid Supplementation: A Legitimate Pharmacotherapy After Neonatal Open Heart Surgery

BACKGROUND

An inflammatory response together with multiple organ failure subsequent to cardiopulmonary bypass is especially prominent in neonates. The behavior of glucocorticoids during this period in these patients is not known. If adrenal insufficiency should exist, it could considerably compromise postoperative recovery.

METHODS

Twenty neonates undergoing biventricular repair were enrolled. Ten patients were assigned to receive hydrocortisone treatment and the other 10 to receive placebo. The treatment group received stress-dose hydrocortisone sodium succinate after discontinuation of cardiopulmonary bypass: 0.18 mg.kg(-1).hr(-1) for 3 days, 0.09 mg.kg(-1).hr(-1) for 2 days, and 0.045 mg.kg(-1).hr(-1) for 2 days. The placebo was 5% glucose solution.

RESULTS

Patients had adrenal insufficiency (cortisol < 5 microg/dL) from 24 to 72 hours in the placebo group. This was associated with a simultaneous reduction of left ventricular shortening fraction (p < 0.0001, analysis of variance; p = 0.0203, Student's t test), the necessity to increase inotropic agents (p = 0.043, analysis of variance), and an increase in serum lactate level (p = 0.049, Student's t test). During this period, serum cortisol level was maintained above the normal level (> 23 microg/dL) in the hydrocortisone group. The placebo group had a greater positive fluid balance (p = 0.027, Student's t test) and greater total body edema in the immediate postoperative period (p = 0.065, Student's t test). Blood oxygenation constantly improved, and the duration on mechanical ventilation was shorter (83.5 +/- 42.1 versus 138.2 +/- 89.7 hours; p = 0.098) in the hydrocortisone group.

CONCLUSIONS

Adrenal insufficiency may occur after neonatal open heart surgery. Stress-dose hydrocortisone supplementation blunts other organ dysfunction and can be considered a legitimate pharmacotherapy in this cohort.

Milrinone and low cardiac output following cardiac surgery in infants: is there a direct myocardial effect?

We assessed the effect of milrinone on myocardial function in pediatric patients with postoperative low cardiac output syndrome by index of myocardial performance in a prospective, open-label, nonrandomized, consecutive study. Fifteen patients with low cardiac output syndrome following cardiac surgical treatment were studied in the tertiary cardiothoracic pediatric intensive care unit between April 2001 and November 2003 (age range, 0.2-16 months; median, 7; weight, 2.7-11.8 kg; median, 5). Echocardiographic, Doppler-derived, time interval-based index of myocardial performance (Tei index) was used to study cardiac function prior to and while on intravenous milrinone treatment for 18-24 hours. Treatment with milrinone led to improvement in biventricular myocardial function [mean right ventricular index from 0.521 (SD-0.213) to 0.385 (SD-0.215), p = 0.003; mean left ventricular index from 0.636 (SD-0.209) to 0.5 (SD-0.171), p = 0.012). No difference was found in the values of heart rate corrected right or left ventricular ejection time prior to and while on treatment with milrinone (right ventricle: mean, 1.23 (SD-0.42) and 1.14 (SD-0.48), p = 0.29; left ventricles: mean, 1.17 (SD-0.51) and 1.13 (SD-0.48), p = 0.66) Our data support the direct myocardial effect of milrinone as part of the mechanism behind its already proven benefit in children with low cardiac output syndrome following cardiac surgery.

Effect of amrinone on mucosal permeability in experimental intestinal ischaemia/reperfusion injury

BACKGROUND

The preventive effect of amrinone on ischaemia/reperfusion (I/R) injury has been shown in the medical literature. The purpose of the present study was to investigate the preventive effect of amrinone on I/R injury of the small bowel of the rat.

METHODS

Thirty-two Wistar albino rats (140-180 g) were divided into four groups (n = 8). In all groups except the sham group the superior mesenteric artery was clamped for 30 min. At the beginning of reperfusion, 1 mL of 2405 Bq/mL 51Cr-ethylenediamine tetra-acetic acid (EDTA) was administered into the prepared ileal segment. Following 30 min of reperfusion, 1 mL of blood was obtained from the portal vein. After the rats were killed, the small intestine was removed for histopathological studies. A total of 5 mg/kg amrinone was administered to the rats in group 1 before ischaemia and in group 2 before reperfusion, whereas only saline was administered to the rats in the control group. Statistical analysis was carried out with Kruskal-Wallis and chi2 test, P < 0.01 was considered significant.

RESULTS

Both the blood 51Cr-EDTA measurements (mean +/- SD) and mucosal injury grades (MIG) were highest in the control group (3.95 +/- 0.71 c.p.m.; MIG, 3-5) followed by group 2 (0.50 +/- 0.35 c.p.m.; MIG, 1-3), group 1 (0.47 +/- 0.34 c.p.m. MIG, 0-3), and sham group (0.12 +/- 0.05 c.p.m.; MIG, 0). The difference between groups 1 and 2 and the control group were statistically significant (P < 0.01 for each comparison). The results of group 1 and 2 were similar statistically (P > 0.05).

CONCLUSIONS

Amrinone was found to be effective in preventing intestinal I/R injury.

Cytokine-Induced Modulation of Cardiac Function

Cytokines act in an autocrine and/or paracrine fashion to induce a diverse variety of biological responses. Several cardiac diseases are associated with cytokine activation, and such activation significantly influences several physiologic parameters, including cardiac mechanical function. This review summarizes the current concepts regarding the modulation of myocardial function by cytokines and provides rationale for the sometimes-conflicting results in the literature regarding underlying mechanisms and patterns of dysfunction. Although traditionally considered cardiodepressant mediators, contractile responses are complex and bimodal, with an early response (within minutes) of variable direction, stimulatory or depressant, depending on the ambient physiologic milieu and relative contributions of the underlying signaling pathways that are activated. These pathways include sphingomyelinase-, nitric oxide (NO)-, and phospholipase A2-dependent signaling with resultant combined effects on contraction and the Ca2+ transient. This is subsequently followed by a profoundly cardiodepressant late response lasting hours to days, depending on the production of secondary mediators and the combined influence of NO generated from inducible NO synthase, reactive oxygen species, and alterations in beta-adrenergic receptor signaling. The interrelationships between these pathways and the time-dependence of their activation are important considerations in the evaluation of cytokine-dependent dysfunction during both acute cardiac injury and chronic cardiac pathologies.

Tumor necrosis factor-alpha is associated with early postresuscitation myocardial dysfunction

OBJECTIVE

Left ventricular dysfunction after successful cardiopulmonary resuscitation contributes to early death following resuscitation. The stress-induced proinflammatory cytokines, particularly tumor necrosis factor-alpha and interleukin-1beta, are known to depress myocardial function. We hypothesized that tumor necrosis factor-alpha and interleukin-1beta, synthesized and released in response to the stress of global ischemia accompanying cardiac arrest, play a role in development of postresuscitation left ventricular dysfunction.

METHODS

Hemodynamic variables, tumor necrosis factor-alpha , interleukin-1beta, interleukin-6 (enzyme-linked immunosorbent assay method), and ionized calcium were measured in ten anesthetized swine before and after 7 mins of cardiac arrest and during the early postresuscitation period (60-90 mins).

RESULTS

Tumor necrosis factor-alpha increased three-fold within 15 mins of restoration of circulation and remained elevated throughout the observation period. A significant negative correlation was observed between tumor necrosis factor-alpha and left ventricular systolic change in pressure over time (r = -.54, p <.001). Interleukin-1beta was undetectable before and after resuscitation, and interleukin-6 was detectable in only two animals after resuscitation. Although a significant decline in ionized calcium was observed and correlated with left ventricular systolic change in pressure over time, an independent role for ionized calcium in postresuscitation left ventricular dysfunction was not demonstrated.

CONCLUSION

Tumor necrosis factor-alpha increases during the early postresuscitation period and may play a role in postresuscitation myocardial dysfunction.

Cardiac rescue with enoximone in volume and catecholamine refractory septic shock

In December 2000 and February 2001, two children with suspected meningococcal disease were admitted to our pediatric intensive unit. Their Glasgow Meningococcal Septicaemia Prognostic score was 12 points. General treatment including antibiotics, steroids in case of meningitis, and fluid replacement, was performed. Despite appropriate volume replacement, intubation and ventilation, noradrenaline and adrenaline continuous infusions < or =1.0 microg/kg/min, and additional bolus infusions, cardiac output deteriorated within minutes in both children. Calcium and bicarbonate were given without sustained effect. Echocardiography demonstrated no pericardial effusion and shortening fraction was <10%. External cardiac massage had to be performed immediately in one case for electromechanical uncoupling. Both patients received a bolus of enoximone 2 mg/kg and 5 mg/kg body weight, respectively, followed by a continuous infusion of 20-23 microg/kg/min. Thereafter, both children had an adequate blood pressure and their shortening fraction increased to >30%. Within minutes, the catecholamine infusion could be reduced in both patients. The children completely recovered from their life-threatening situations. In patients with severe prolonged catecholamine and volume refractory endotoxin shock in Waterhouse-Friderichsen syndrome, even with electromechanical uncoupling and complete myocardial arrest, enoximone can immediately restore myocardial contractility.

Impairment of beta-adrenergic signaling in healthy peripheral blood mononuclear cells exposed to serum from patients with septic shock: involvement of the inhibitory pathway of adenylyl cyclase stimulation

The objective of this study was to determine whether the serum of patients with sepsis could alter the capability of healthy human peripheral blood mononuclear cells (PBMC) to synthesize cAMP in response to beta-adrenergic stimulation and to evaluate the involvement of the inhibitory pathway (Gi) of adenylyl cyclase in the sepsis-induced alteration of beta-adrenergic signaling. First, PBMC from a healthy donor were incubated for 24 h in serum-containing medium according to three culture conditions: serum alone, serum with pertussis toxin, and serum with propranolol. Second, PBMC were stimulated with 10(-5) M isoproterenol or 10(-6) M forskolin, and measurement of cyclic adenosine monophosphate (cAMP) intracellular accumulation was performed. Serum samples were obtained from three groups of subjects: 14 patients with severe sepsis, 21 patients with septic shock, and 10 healthy control subjects. Basal and forskolin-stimulated cAMP levels were similar in PBMC cultured in control or in septic serum. Isoproterenol-stimulated accumulation was reduced in PBMC preincubated in septic serum. The lowest cAMP levels were found after exposure to serum from patients with septic shock. The addition of pertussis toxin in the incubation medium constantly increased cAMP response to isoproterenol, but more significantly in PBMC exposed to septic serum. Incubation in the presence of propranolol had no significant effect. The serum of patients with sepsis contained soluble depressant substances that inhibited adenylyl cyclase activation by beta-adrenergic agonists. Septic shock serum exhibited the most potent inhibitory effect. Hyperactivation of the Gi pathway of adenylyl cyclase was mainly responsible for the altered transmembrane beta-adrenergic signaling.

Effects of cAMP modulators on long-chain fatty-acid uptake and utilization by electrically stimulated rat cardiac myocytes

Recently, we established that cellular contractions increase long-chain fatty-acid (FA) uptake by cardiac myocytes. This increase is dependent on the transport function of an 88 kDa membrane FA transporter, FA translocase (FAT/CD36), and, in analogy to skeletal muscle, is likely to involve its translocation from an intracellular pool to the sarcolemma. In the present study, we investigated whether cAMP-dependent signalling is involved in this translocation process. Isoproterenol, dibutyryl-cAMP and the phosphodiesterase (PDE) inhibitor, amrinone, which markedly raised the intracellular cAMP level, did not affect cellular FA uptake, but influenced the fate of intracellular FAs by directing these to mitochondrial oxidation in electrostimulated cardiac myocytes. The PDE inhibitors 3-isobutyl-1-methylxanthine, milrinone and dipyridamole each significantly stimulated FA uptake as well as intracellular cAMP levels, but these effects were quantitatively unrelated. The stimulatory effects of these PDE inhibitors were antagonized by sulpho- N -succinimidylpalmitate, indicating the involvement of FAT/CD36, albeit that the different PDE inhibitors use different molecular mechanisms to stimulate FAT/CD36-mediated FA uptake. Notably, 3-isobutyl-1-methylxanthine and milrinone increased the intrinsic activity of FAT/CD36, possibly through its covalent modification, and dipyridamole induces translocation of FAT/CD36 to the sarcolemma. Elevation of intracellular cGMP, but not of cAMP, by the PDE inhibitor zaprinast did not have any effect on FA uptake and metabolism by cardiac myocytes. The stimulatory effects of PDE inhibitors on cardiac FA uptake should be considered when applying these agents in clinical medicine.

Heart failure in pediatric septic shock: utilizing inotropic support

Septic shock presents a unique challenge in the pediatric patient. Sepsis stimulates the release of inflammatory mediators that can compromise cardiac function. Oxygen extraction abnormalities, diminished responses to adrenergic agonists, and impaired ventricular function often result. After fluid resuscitation and antibiotic therapy, careful cardiovascular assessment is needed to administer appropriate inotropic and vasoactive drugs.

Amrinone in pediatric refractory septic shock: An open-label pharmacodynamic study

OBJECTIVE: To investigate the short-term hemodynamic effects of amrinone in pediatric patients with refractory septic shock. DESIGN: Open-label, clinical trial. SETTING: Pediatric intensive care unit. PATIENTS: Nine patients admitted with a diagnosis of septic shock receiving stable doses of vasopressors and inotropes. INTERVENTIONS: Pediatric patients with septic shock and a pulmonary artery catheter were treated with amrinone in a stepwise fashion at 5, 10, and 15 &mgr;g/kg/min. MEASUREMENTS AND MAIN RESULTS: Heart rate, blood pressure, cardiac index, rate pressure product, systemic vascular resistance index, pulmonary vascular resistance, oxygen delivery, and oxygen consumption were measured at baseline and 90 mins after each amrinone dose. The addition of amrinone increased cardiac index (p <.05) and oxygen delivery (p <.05) without increasing the rate pressure product. Decreases were observed in systemic vascular resistance index (p <.05) and pulmonary vascular resistance (p <.05). No significant changes were seen in heart rate, blood pressure, or oxygen consumption. CONCLUSIONS: In this short-term, dose-response study in children with refractory septic shock, amrinone improved cardiac index and oxygen delivery in pediatric patients with refractory septic shock without increasing myocardial work.

Stimulation of beta-adrenergic receptors inhibits the release of tumor necrosis factor-alpha from the isolated rat heart

OBJECTIVES

Beta-adrenergic receptor agonists such as isoproterenol inhibit production of tumor necrosis factor (TNF)-alpha in a number of cell types. Because the heart is a source of TNF-alpha, we hypothesized that isoproterenol would inhibit cardiac production of the cytokine.

DESIGN

Analysis of cardiac release of TNF-alpha.

SETTING

Medical research laboratory.

SUBJECTS

Rats.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

With the approval of the Institutional Animal Care and Use Committee, rats were anesthetized and hearts were removed and perfused. After 30 mins, bacterial lipopolysaccharide (LPS) with or without isoproterenol was infused for 60 mins. At 30, 60, 90, 120, and 150 mins, coronary flow was measured and coronary effluent was analyzed for TNF-alpha. Cardiac production of TNF-alpha was expressed as pg/min. Cyclic adenosine monophosphate (AMP) in the coronary effluent was measured. TNF-alpha messenger RNA was determined in ventricular tissue. After 30 mins, TNF-alpha was undetectable in the coronary effluent However, 60 mins after the initiation of LPS infusion, TNF-alpha release was 875+/-255 pg/min and increased to 2164+/-721 pg/min at 150 mins. Simultaneous infusion of isoproterenol with LPS stimulated cyclic AMP release and inhibited TNF-alpha production. For instance, at 60 and 150 mins, TNF-alpha release was 75+/-38 and 58+/-29 pg/min, respectively (p < .05 vs. LPS alone). Simultaneous infusion of isoproterenol with LPS blocked the induction of TNF-alpha messenger RNA by LPS. Isoproterenol, begun 30 mins after the initiation of LPS infusion, still suppressed LPS-stimulated TNF-alpha release by 95% at 150 mins. Similar results were obtained with norepinephrine.

CONCLUSIONS

Activation of beta-adrenergic receptors inhibits cardiac TNF-alpha release. This implies that cytokine production by the heart is inhibited by the sympathetic nervous system. In heart failure, the cardiac response to the sympathetic nervous system is impaired. This impairment may play a role in the high plasma levels of TNF-alpha found in heart failure.

Myocardial dysfunction in septic shock

Over the last decade, it has become clear that myocardial depression, like vascular dysfunction, is typical of human septic shock. Human septic myocardial depression is characterized by reversible biventricular dilatation, decreased ejection fraction, and decreased response to fluid resuscitation and catecholamine stimulation (in the presence of overall hyperdynamic circulation). A circulating myocardial depressant substance, not myocardial hypoperfusion, is responsible for this phenomenon. This substance has been shown to represent low concentrations of TNF-alpha and IL-1 beta acting in synergy on the myocardium through mechanisms that include NO and cGMP generation. Despite major advances in our understanding of the hemodynamics and pathogenesis of cardiac dysfunction in sepsis, successful attempts to modulate these mechanisms to improve clinical outcomes in human trials have not been demonstrated to date. For the moment, the therapeutic approach to the patient with cardiac dysfunction in distributive or septic shock must be primarily aimed at reestablishing adequate organ perfusion and oxygen delivery by vigorous fluid resuscitation and vasopressor or inotropic support. In the long term, however, only continued research regarding the cellular mechanisms of organ dysfunction, including septic myocardial depression, will lead to successful therapeutic strategies. These strategies will likely involve direct manipulation of intracellular signaling processes that lead to organ dysfunction as manifested by septic myocardial dysfunction and septic shock.