Effect of levosimendan on balance between ATP production and consumption in isolated perfused guinea-pig heart before ischemia or after reperfusion

Effect of intravenous levosimendan or milrinone on left atrial pressure in patients undergoing off-pump coronary artery bypass grafting-A prospective double-blind, randomized controlled trial

Background

Maintaining a low left atrial pressure (LAP) in off-pump coronary artery bypass grafting (OPCAB) is desirable. This study was done to compare the effects of intravenous levosimendan or milrinone on LAP at different stages of OPCAB.

Materials and Methods

After institutional ethics committee clearance, this two-arm double-blind randomized control trial was done in 44 adult patients with triple vessel coronary artery disease undergoing OPCAB at cardiac OT of IPGME&R, Kolkata. The patients were randomly allocated into two groups receiving intraoperative either levosimendan or milrinone. Pulmonary capillary wedge pressure (PCWP) was compared as the primary outcome parameter, whereas other echocardiographic and hemodynamic parameters were also assessed during six stages of OPCAB, that is, after sternotomy, proximal(s), left anterior descending artery (LAD), obtuse marginal (OM), posterior descending artery (PDA) grafting, and before sternal closure. Numerical parameters were compared using Student's unpaired two-tailed t-test.

Results

PCWP was found to be significantly lower (P < 0.05) in the levosimendan group during proximal (P = 0.047), LAD (P = 0.018), OM (P < 0.0001), PDA grafting (P = 0.028), and before sternal closure (P = 0.015). Other parameters indicate LAP, that is, from mitral early diastolic inflow velocity to mitral annular early diastolic velocity ratio (E/e'), which indicated significantly lower LAP in levosimendan group during LAD, OM, and PDA grafting and before sternal closure. Conclusion: Levosimendan may be used as a primary inotrope in terms of better reduction in left atrial pressure during different stages of OPCAB, translating to a decrease in left ventricular end-diastolic pressure, therefore maintaining optimum coronary perfusion pressure, which is the primary goal of the surgery.

The role of levosimendan in phosphine-induced cardiotoxicity: evaluation of electrocardiographic, echocardiographic, and biochemical parameters

Aluminum phosphide (AlP) causes serious poisoning in which severe cardiac suppression is the significant lethal consequence. According to evidence, levosimendan can exert outstanding cardiac support and protection in different pathological conditions. This study aimed to investigate the mechanisms by which levosimendan may alleviate cardiovascular toxicity due to AlP intoxication in the rat model. The groups included control group (normal saline only), sole levosimendan groups (12, 24, 48 μg/kg), AlP group (10 mg/kg), and AlP + levosimendan groups receiving 12, 24, 48 μg/kg levosimendan intraperitoneally 30 min after AlP administration. Electrocardiographic (ECG) parameters (QRS and PR duration and ST height), heart rate, and blood pressure were monitored for 180 minutes. Also, after 24 h of poisoning, echocardiography was applied to assess left ventricle function. Evaluation of the biochemical parameters in heart tissue, including mitochondrial complexes I, II, IV activity, ADP/ATP ratio, the rate of apoptosis, malondialdehyde (MDA), lactate, and troponin I levels, were done after 12 and 24 h. AlP-induced ECG abnormalities (PR duration and ST height), reduction in heart rate, blood pressure, cardiac output, ejection fraction, and stroke volume were improved by levosimendan administration. Besides, levosimendan significantly improved complex IV activity, the ADP/ATP ratio, apoptosis, MDA, lactate, and troponin I level following AlP-poisoning. Our results suggest that levosimendan might alleviate AlP-induced cardiotoxicity by modulating mitochondrial activity and improving cardiac function. However, the potential clinical use of levosimendan in this toxicity needs more investigations.

Levosimendan Improves Oxidative Balance in Cardiogenic Shock/Low Cardiac Output Patients

The beneficial effects exerted by levosimendan against cardiac failure could be related to the modulation of oxidative balance. We aimed to examine the effects of levosimendan in patients with cardiogenic shock or low cardiac output on cardiac systo-diastolic function and plasma oxidants/antioxidants (glutathione, GSH; thiobarbituric acid reactive substances, TBARS). In four patients undergoing coronary artery bypass grafting or angioplasty, cardiovascular parameters and plasma GSH and TBARS were measured at T0 (before levosimendan infusion), T1 (1 h after the achievement of the therapeutic dosage of levosimendan), T2 (end of levosimendan infusion), T3 (72 h after the end of levosimendan infusion), and T4 (end of cardiogenic shock). We found an improvement in the indices of systolic (ejection fraction, cardiac output, cardiac index) and diastolic (E to early diastolic mitral annular tissue velocity, E/'; early to late diastolic transmitral flow velocity, EA) cardiac function at early T2. A reduction of central venous pressure and pulmonary wedge pressure was also observed. Plasma levels of GSH and TBARS were restored by levosimendan at T1, as well. The results obtained indicate that levosimendan administration can regulate oxidant/antioxidant balance as an early effect in cardiogenic shock/low cardiac output patients. Modulation of oxidative status on a mitochondrial level could thus play a role in exerting the cardio-protection exerted by levosimendan in these patients.

Use of Levosimendan in Intensive Care Unit Settings: An Opinion Paper

Levosimendan is an inodilator that promotes cardiac contractility primarily through calcium sensitization of cardiac troponin C and vasodilatation via opening of adenosine triphosphate–sensitive potassium (K_ATP) channels in vascular smooth muscle cells; the drug also exerts organ-protective effects through a similar effect on mitochondrial K_ATP channels. This pharmacological profile identifies levosimendan as a drug that may have applications in a wide range of critical illness situations encountered in intensive care unit medicine: hemodynamic support in cardiogenic or septic shock; weaning from mechanical ventilation or from extracorporeal membrane oxygenation; and in the context of cardiorenal syndrome. This review, authored by experts from 9 European countries (Austria, Belgium, Czech republic, Finland, France, Germany, Italy, Sweden, and Switzerland), examines the clinical and experimental data for levosimendan in these situations and concludes that, in most instances, the evidence is encouraging, which is not the case with other cardioactive and vasoactive drugs routinely used in the intensive care unit. The size of the available studies is, however, limited and the data are in need of verification in larger controlled trials. Some proposals are offered for the aims and designs of these additional studies.

Levosimendan in patients with reduced left ventricular function undergoing isolated coronary or valve surgery

OBJECTIVE

In the Levosimendan in Patients with Left Ventricular Systolic Dysfunction Undergoing Cardiac Surgery Requiring Cardiopulmonary Bypass (LEVO-CTS) trial, no differences in clinical outcomes were observed between levosimendan and placebo in a broad population of patients undergoing cardiac surgery. In previous studies, the benefits of levosimendan were most clearly evident in patients undergoing isolated coronary artery bypass grafting (CABG) surgery. In a prespecified analysis of LEVO-CTS, we compared treatment-related outcomes and costs across types of cardiac surgical procedures.

METHODS

Overall, 563 (66.4%) patients underwent isolated CABG, 97 (11.4%) isolated valve, and 188 (22.2%) combined CABG/valve surgery. Outcomes included the co-primary 4-component composite (30-day mortality, 30-day renal replacement, 5-day myocardial infarction, or 5-day mechanical circulatory support), the 2-component composite (30-day mortality or 5-day mechanical circulatory support), 90-day mortality, low cardiac output syndrome (LCOS), and 30-day medical costs.

RESULTS

The 4- and 2-component outcomes were not significantly different with levosimendan and placebo in patients undergoing CABG (15.2% vs 19.3% and 7.8% vs 10.4%), valve (49.0% vs 33.3% and 22.4% vs 2.1%), or combined procedures (39.6% vs 35.9% and 24.0% vs 19.6%). Ninety-day mortality was lower with levosimendan in isolated CABG (2.1% vs 7.9%; hazard ratio [HR], 0.26; 95% confidence interval [CI], 0.11-0.64), but not significantly different in valve (8.3% vs 2.0%; HR, 4.10; 95% CI, 0.46-36.72) or combined procedures (10.4% vs 7.6%; HR, 1.39; 95% CI, 0.53-3.64; interaction P = .011). LCOS (12.0% vs 22.1%; odds ratio, 0.48; 95% CI, 0.30-0.76; interaction P = .118) was significantly lower in levosimendan-treated patients undergoing isolated CABG. Excluding study drug costs, median and mean 30-day costs were $53,707 and $65,852 for levosimendan and $54,636 and $67,122 for placebo, with a 30-day mean difference (levosimendan - placebo) of -$1270 (bootstrap 95% CI, -$8722 to $6165).

CONCLUSIONS

Levosimendan was associated with lower 90-day mortality and LCOS in patients undergoing isolated CABG, but not in those undergoing isolated valve or combined CABG/valve procedures.

Use of levosimendan in acute heart failure

As a calcium sensitizer and inodilator that augments cardiac contractility without increasing myocardial oxygen demand or exacerbating ischaemia, levosimendan may be well configured to deliver inotropic support in cases of acute heart failure (AHF). Other factors favouring levosimendan in this setting include its extended duration of action due to the formation of an active metabolite and the lack of any attenuation of effect in patients treated with beta-blockers. Effects of levosimendan on systemic haemodynamics include its significant, dose-dependent increases in cardiac output, stroke volume and heart rate, and decreases in right and left ventricular filling and total peripheral resistance. Rapid and sustained reduction in levels of natriuretic peptides is a consistent effect of levosimendan use and potentially favourable effects on other neurohormonal indicators of cardiac distress are also observed. Levosimendan has repeatedly been shown to be effective in relief of symptoms of AHF, notably dyspnoea and fatigue, while mortality data from clinical trials and registries suggest that levosimendan is markedly less likely than catecholaminergic inotropes to worsen prognosis. The vasodilator pharmacology of levosimendan is also pertinent to the drug’s use in AHF, in which setting organ under-perfusion is often a key pathology. These considerations suggest that levosimendan may have a more favourable impact on the circumstances of the majority of AHF patients than adrenergic agents that act only or primarily as cardiac stimulants. They also suggest that levosimendan may advantageously be integrated into a comprehensive strategy of early intervention designed and intended to prevent cardiac destabilization worsening to the point where hospitalization is necessary. Levosimendan should be used with caution and with tightened haemodynamic monitoring in patients who have low baseline blood pressure (systolic blood pressure <100 mmHg; diastolic blood pressure <60 mmHg), or who are at risk of a hypotensive episode.

Prophylactic preoperative levosimendan for off-pump coronary artery bypass grafting in patients with left ventricular dysfunction: Single-centered randomized prospective study

Background:

Off-pump coronary artery bypass surgery (OPCAB) is often complicated by hemodynamic instability, especially in patients with prior left ventricular (LV) dysfunction and appropriate choice of inotrope plays a vital role in perioperative management of these patients.

Aim and Objective:

To study hemodynamic effects and immediate outcome of prophylactic infusion of levosimendan in patients with the LV dysfunction undergoing OPCAB surgery and whether this strategy helps in successful conduct of OPCAB surgery.

Materials and Methods:

After Institutional Ethics Committee approval, 60 patients posted for elective OPCAB surgery were randomly divided into two groups (n = 30 each). Patients with the LV ejection fraction <30% were included. Study group was started on injection levosimendan (@ 0.1 μg/kg/min) in the previous night before surgery and continued for 24 h including intraoperative period. Hemodynamic monitoring included heart rate, invasive blood pressure, cardiac index (CI), pulmonary capillary wedge pressure (PCWP), pulse oximetry, and arterial blood gases with serum lactates at as T0 (baseline), T1 (15 min after obtuse marginal and/or PDA anastomoses), T2 (at end of surgery), T3 (6 h after surgery in Intensive Care Unit [ICU]), T4 (12 h after surgery), and T5 (24 h after surgery in ICU). Vasopressor was added to maintain mean arterial pressure >60 mmHg. Chi-square/Fisher's exact/Mid P exact test and Student's t-tests were applied for categorical and continuous data.

Results:

CI was greater and PCWP reduced significantly in Group L during intraoperative and early postoperative period. Serum lactate concentration was lower in patients pretreated with levosimendan. Incidence of postoperative atrial fibrillation (POAF) (36.6 vs. 6.6%; P = 0.01), low cardiac output syndrome (LCOS) (30% vs. 6%; P = 0.02), and acute kidney injury (23.3% vs. 6.7%; P = 0.04) was less in Group L. Three patients (10%) in control group required conversion to cardiopulmonary bypass (CPB) as compared to none in the study group. There was no difference regarding ICU or hospital stay and mortality in both groups.

Conclusion:

Preoperative levosimendan helps in successful conduct of OPCAB and reduces the incidence of LCOS, POAF, conversion to CPB, and requirement of intra-aortic balloon pump.

Preoperative optimization with levosimendan in heart failure patient undergoing thoracic surgery

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The use of levosimendan for perioperative optimization of patients undergoing cardiac surgery has been reported in several studies, however it has not been thouroughly evaluated in cardiac failure patients undergoing non cardiac surgery.

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Preoperative levosimendan administration is safe and effective in cardiac failure patient undergoing thoracic surgery.

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Prophylactic preoperative levosimendan treatment in heart failure patients merits further study.

Introduction

We present the case of a patient with dilatative cardiomyopathy waiting for heart transplantation with pleural effusion to be subjected to pleural biopsy, treated with preoperative infusion of levosimendan to improve heart performances.

Presentation of case

A 56-year-old man (BMI 22,49) with dilatative cardiomyopathy (EF 18%) presented right pleural effusion. The levosimendan treatment protocol consisted of 24 h continuous infusion (0,1 ug/kg/min), without bolus. The patient was under continuous hemodynamic monitoring prior, during and after levosimendan administration. The surgery for pleural biopsy was performed with uniportal Video Assisted Thoracoscopic approach (VATS).

Discussion

A significant increase of Cardiac Index (CI) and Stroke Volume Index (SVI) were observed at 4 h after infusion initiation and was sustained during the next 24 h after the end of infusion. Levosimendan administration was safe.

Conclusion

In this case the prophylactic preoperative levosimendan administration is safe and effective in cardiac failure patient undergoing thoracic surgery, but prophylactic preoperative levosimendan treatment in these patients merits further study.

Effect of Levosimendan and Milrinone on Regional Myocardial Ischemia/Reperfusion-Induced Arrhythmias in Dogs

Phosphodiesterase inhibitors as inodilators in heart failure are associated with promotion of arrhythmias. Calcium sensitizers have been proposed for the treatment of severe decompensated heart failure. The effect of levosimendan, a calcium sensitizer, and milrinone, a phosphodiesterase inhibitor, on ventricular arrhythmias was compared in a model of acute regional myocardial ischemia and reperfusion. The left anterior descending coronary artery in dogs was occluded for 25 minutes, followed by reperfusion. The 2 drugs were administered in a hemodynamically equieffective dose (0.1 μmol/kg) 10 minutes before coronary occlusion. Levosimendan, but not milrinone, significantly attenuated the pronounced increase in the number of ventricular premature beats (-63%), tachycardia (-50%), fibrillation (-70%), and inhomogeneity of ventricular electrical activation. Levosimendan significantly improved the overall survival rate. Levosimendan has a more beneficial profile than milrinone regarding the development of ventricular arrhythmias during and after regional myocardial ischemia

Levosimendan Reduces Mortality in Adults with Left Ventricular Dysfunction Undergoing Cardiac Surgery: A Systematic Review and Meta-analysis

INTRODUCTION

Levosimendan is implemented in patients with low cardiac output after cardiac surgery. However, the strength of evidence is limited by randomized controlled trials enrolling a small number of patients. Hence we have conducted a systematic review to determine the role of levosimendan in adult cardiac surgery.

METHODS

PUBMED, WoS, Cochrane database, and SCOPUS were systematically queried to identify original English language peer-reviewed literature (inception-October 2014) comparing clinical results of adult cardiac surgery between levosimendan and control. Pooled odds ratio (OR) was calculated using the Peto method; p < 0.05 is significant; results are presented within 95% confidence intervals. Continuous data was compared using standardized mean difference/mean difference.

RESULTS

Fourteen studies were included in the analysis. Levosimendan reduced early mortality in patients with reduced ejection fraction (5.5% vs. 9.1%) (OR 0.48 [0.23-0.76]; p = 0.004). This result was confirmed using sensitivity analysis. Postoperative acute renal failure was lower with levosimendan therapy (7.4% vs. 11.5%). Intensive care unit stay was shorter in the levosimendan cohort comparable in both groups (standardized mean difference -0.31 [-0.53, -0.09]; p = 0.006; I(2)  = 33.6%). Levosimendan-treated patients stayed 1.01 (1.61-0.42) days shorter when compared to control (p = 0.001).

CONCLUSION

Our meta-analysis demonstrates that Levosimendan improves clinical outcomes in patients with left ventricular dysfunction undergoing cardiac surgery. Results of the ongoing multicenter randomized controlled trial are awaited to provide more conclusive evidence regarding the benefit of this drug.

Inhibition of reverse-mode sodium-calcium exchanger activity and apoptosis by levosimendan in human cardiomyocyte progenitor cell-derived cardiomyocytes after anoxia and reoxygenation

Levosimendan, a known calcium sensitizer with positive inotropic and vasodilating properties, might also be cardioprotective during ischemia-reperfusion (I/R) insult. Its effects on calcium homeostasis and apoptosis in I/R injury remain unclear. Na(+)/Ca(2+) exchanger (NCX) is a critical mediator of calcium homeostasis in cardiomyocytes, with reverse-mode NCX activity responsible for intracellular calcium overload and apoptosis of cardiomyocytes during I/R. We probed effects and underlying mechanisms of levosimendan on apoptosis and NCX activity in cultured human cardiomyocyte progenitor cells (CPC)-derived cardiomyocytes undergoing anoxia-reoxygenation (A/R), simulating I/R in vivo. Administration of levosimendan decreased apoptosis of CPC-derived cardiomyocytes induced by A/R. The increase in reverse-mode NCX activity after A/R was curtailed by levosimendan, and NCX1 was translocated away from the cell membrane. Concomitantly, endoplasmic reticulum (ER) stress response induced by A/R was attenuated in CPC-derived cardiomycytes treated with NCX-targeted siRNA or levosimendan, with no synergistic effect between treatments. Results indicated levosimendan inhibited reverse-mode NCX activity to protect CPC-derived cardiomyocytes from A/R-induced ER stress and cell death.

Absence of mitochondrial activation during levosimendan inotropic action in perfused paced guinea pig hearts as demonstrated by modular control analysis

Levosimendan is a calcium sensitizer developed for the treatment of heart failure. It increases contractile force by enhancing the sensitivity of myofilaments to calcium. Besides this sensitizing effect, the drug has also been reported to show some inhibitory action on phosphodiesterase 3 (PDE3). The inotropic effects of levosimendan have been studied on guinea pig paced perfused hearts by using modular control analysis (MoCA) (Diolez P, Deschodt-Arsac V, Raffard G, Simon C, Santos PD, Thiaudiere E, Arsac L, Franconi JM. Am J Physiol Regul Integr Comp Physiol 293: R13-R19, 2007.), an integrative approach of heart energetics using noninvasive (31)P NMR. The aim was to evaluate quantitatively the respective effects of this drug on energy supply and demand modules. Under our experimental conditions, 0.7 muM levosimendan induced a 45% increase in paced heart output associated with a 7% decrease in phosphocreatine and a negligible increase in oxygen consumption. Because MoCA allows in situ study of the internal regulations in intact beating heart energetics, it was applied to describe quantitatively by which routes levosimendan exerts its inotropic action. MoCA demonstrated the absence of any significant effect of the drug on the supply module, which is responsible for the lower increase in oxygen consumption, compared with epinephrine, which increases the ratio between myocardial oxygen consumption and cardiac contraction. This result evidences that, under our conditions, a possible effect of levosimendan on PDE3 activity and/or intracellular calcium remains very low on mitochondrial activity and insignificant on integrated cardiac energetics. Thus, levosimendan inotropic effect on guinea pig heart depends almost entirely on the calcium-sensitizing properties leading to myofilament activation and the concomitant activation of energy supply by the decrease in PCr, therefore improving energetic efficiency of contraction.

Inoprotection: the perioperative role of levosimendan

Levosimendan is emerging as a novel cardioprotective inotrope. Levosimendan augments myocardial contractility by sensitising contractile myofilaments to calcium without increasing myosin adenosine triphosphatase activity or oxygen consumption. Levosimendan activates cellular adenosine triphosphate-dependent potassium channels, a mechanism which is postulated to protect cells from ischaemia in a manner similar to ischaemic preconditioning. Levosimendan may therefore protect the ischaemic myocardium during ischaemia-reperfusion as well as improve the contractile function of the heart. Adenosine triphosphate-dependent potassium channel activation by levosimendan may also be protective in other tissues, such as coronary vascular endothelium, kidney and brain. Clinical trials in patients with decompensated heart failure and myocardial ischaemia show levosimendan to improve haemodynamic performance and potentially improve survival. This paper reviews the known pharmacology of levosimendan, the clinical experience with the drug to date and the potential use of levosimendan as a cardioprotective agent during surgery.

Myocardial stunning following no flow ischaemia is diminished by levosimendan or cariporide, without benefits of combined administration

AIM OF THE STUDY

Levosimendan, a calcium sensitiser, and cariporide, a blocker of the Na+/H+ exchanger, decrease necrosis and improve function following myocardial ischaemia. However, their role in myocardial stunning is unclear. We tested the hypothesis that levosimendan, cariporide, or their combination reduce stunning after global myocardial ischaemia.

METHODS

In a prospective, controlled, randomised laboratory study isolated guinea pig hearts (n=48) were perfused in a Langendorff apparatus. Stunning was induced by 20 min of global no-flow ischaemia. Levosimendan (0.1 micromol/l) or cariporide (1 micromol/l) were given either before or after ischaemia, and effects of both drugs combined were also assessed. Left ventricular developed pressure (LVdp) was assessed continuously before ischaemia and for 45 min after reperfusion.

RESULTS

Levosimendan (24+/-7%) and the combination of levosimendan and cariporide (38.7+/-4%) increased LVdp from baseline values before ischaemia, without differences between groups. In contrast, cariporide alone decreased LVdp (-11+/-2%) from baseline. Ischaemia/reperfusion decreased LVdp by about 70% in vehicle treated hearts compared to baseline. Treatment with cariporide, levosimendan, or their combination both before and after ischaemia, and treatment with cariporide after ischaemia caused a 25% greater recovery of LVdp than in control hearts. There were no differences between these groups and no enhanced effect with levosimendan/cariporide combined. In contrast, levosimendan only given after ischaemia did not improve LVdp.

CONCLUSIONS

Cariporide diminished stunning when given before or after ischaemia, while levosimendan was only effective if given before ischaemia. Thus, levosimendan or cariporide may be useful in settings where ischaemia/reperfusion is to be expected.

The cardioprotective effects of levosimendan: preclinical and clinical evidence

Levosimendan, a drug used in the treatment of acute and decompensated heart failure, has positive inotropic and antistunning effects mediated by calcium sensitization of contractile proteins, and vasodilatory and antiischemic effects mediated via the opening of ATP-sensitive potassium channels in vascular smooth-muscle cells. Recently, it also has been shown to act on mitochondrial ATP-sensitive potassium (mitoKATP) channels, an action thought to protect the heart against ischemia-reperfusion damage. This finding has suggested a possible application for levosimendan in clinical situations in which preconditioning would be beneficial (eg, in pre- and perioperative settings in cardiac surgery). The demonstration that levosimendan can prevent or limit myocyte apoptosis via the activation of mitoKATP channels provides a potential mechanism whereby this agent might protect cardiac myocytes during episodes of acute heart failure. This finding may explain why short-term treatment with levosimendan may improve longer-term survival. The present article reviews the literature on the cardioprotective actions of levosimendan, with particular emphasis on its recently recognized effects on mitoKATP channels and the putative preconditioning effects of that action. A therapeutic approach to acute heart failure that includes a cardioprotective strategy could have a clinically meaningful benefit on disease progression beyond alleviation of symptoms.

Pharmacological preconditioning by levosimendan is mediated by inducible nitric oxide synthase and mitochondrial KATP channel activation in the in vivo anesthetized rabbit heart model

BACKGROUND

Provocation of fatal cardiac arrhythmias has limited the use of inotropic agents as heart failure therapy. Levosimendan (LEV) is a new inodilator, whose mechanism of action includes calcium sensitization of contractile proteins and the opening of ATP-dependent potassium channels.

OBJECTIVES AND METHODS

The aim of this investigation was to test whether the administration of LEV has cardioprotective and antiarrhythmic effects against ischemia and reperfusion injury in a manner similar to ischemic preconditioning (IPC) in a well-standardized model of reperfusion arrhythmias in anesthetized adult male rabbits (n=122) subjected to 30 min occlusion of the left coronary artery followed by 120 min of reperfusion.

RESULTS

Pretreatment with either 1 cycle of IPC, LEV (0.1 micromol/kg, i.v.), or IPC+LEV prior to the period of coronary occlusion offers significant infarct size reduction (21.6+/-1.6%, 22.1+/-2.2%, and 21.4+/-1.4%, respectively vs 38.7+/-3.6% in saline control group; P<0.01) and antiarrhythmic effects. IPC, LEV and IPC+LEV treatment significantly attenuated the incidence of life-threatening arrhythmias like sustained VT (13%, 13% and 13%, respectively vs 100% in saline control group; P<0.005) and other arrhythmias (25%, 25% and 13%, respectively vs 100% in saline control group; P<0.005), and increased the number of surviving animals without arrhythmias. Pretreatment with 5-HD, N(omega)-nitro-L-arginine methyl ester (L-NAME, a nonspecific NOS inhibitor) and the specific iNOS inhibitor 1400 W [N-(-3-(aminomethyl)benzyl) acetamidine] abolished the beneficial effects of IPC, and LEV on reperfusion induced arrhythmias and cardioprotection suggesting that benefits have been achieved via both the selective activation of cardiomyocyte mitochondrial K(ATP) channels and NO. One cycle of IPC and LEV pretreatment significantly preserved the level of ATP in the 30 min ischemic heart and 120 min reperfused heart.

CONCLUSIONS

The present study demonstrates similarities between acute LEV treatment and IPC of the rabbit myocardium in terms of survival, cardioprotection, antiarrhythmic activity, and metabolic status.

Levosimendan: beyond its simple inotropic effect in heart failure

Classic inotropic agents provide short-term haemodynamic improvement in patients with heart failure, but their use has been associated with poor prognosis. A new category of inotropic agents, the Ca(2+) sensitizers, may provide an alternative longer lasting solution. Levosimendan is a relatively new Ca(2+) sensitizer which offers haemodynamic and symptomatic improvement by combining a positive inotropic action via Ca(2+) sensitization and a vasodilatory effect via adenosine triphosphate(ATP)-sensitive K(+) (K(ATP)), Ca(2+)-activated K(+) (K(Ca)(2+)) and voltage-dependent K(+) (K(V)) channels activation. Levosimendan also seems to induce a prolonged haemodynamic improvement in patients with heart failure as a result of the long half-life of its active metabolite, OR-1896. Furthermore, there is also evidence that levosimendan may have additional antiinflammatory and antiapoptotic properties, affecting important pathways in the pathophysiology of heart failure. Despite the initial reports for a clear benefit of levosimendan on short- and long-term mortality in patients with severe heart failure, the results from the recent clinical trials are rather disappointing, and it is still unclear whether it is superior to dobutamine in affecting survival of patients with severe heart failure. In conclusion, levosimendan is a promising agent for the treatment of decompensated heart failure. As further to its positive inotropic effect, it affects multiple pathways with key roles in the pathophysiology of heart failure. The results of the ongoing trials examining the effect of levosimendan on mortality in patients with heart failure will hopefully resolve the controversy as to whether levosimendan is superior to classic inotropic agents for the treatment of severe heart failure.

Pharmacological Mechanisms Contributing to the Clinical Efficacy of Levosimendan

Acute decompensation of chronic heart failure is a direct life-threatening situation with short-term mortality approaching 30%. A number of maladaptive changes are amplified within the cardiovascular system during the progression of chronic heart failure that makes the decompensation phase difficult to handle. Levosimendan is a new Ca2+-sensitizer for the treatment of acutely decompensated heart failure that has proved to be effective during the decompensation of chronic heart failure and acute myocardial infarction. Levosimendan differs from other cardiotonic agents that are used for acute heart failure in that it utilizes a unique dual mechanism of action: Ca2+-sensitization through binding to troponin C in the myocardium, and the opening of ATP-sensitive K+ channels in vascular smooth muscle. In general, these mechanisms evoke positive inotropy and vasodilation. Clinical studies suggested long-term benefits on mortality following short-term administration. It may, therefore, be inferred that levosimendan has additional effects on the cardiovascular system that are responsible for the prolongation of survival. Results of preclinical and clinical investigations suggest that the combination of levosimendan-induced cardiac and vascular changes has favorable effects on the coronary, pulmonary and peripheral circulations. Redistribution of the circulating blood offers an improved hemodynamic context for the development of a positive inotropic effect through Ca2+-sensitization of the contractile filaments, without a proportionate increase in myocardial oxygen consumption or the development of arrhythmias. Activation of ATP-sensitive K+ channels, both on sarcolemma and mitochondria, may protect against myocardial ischemia, and decreased levels of cytokines may prevent the development of further myocardial remodeling. Collectively, these effects of levosimendan shift the disturbed cardiovascular parameters towards normalization, thereby halting the perpetuation of the vicious cycle of heart failure progression. This may contribute to stabilization of the circulation and improved life expectancy of patients with chronic heart failure.

Newer approaches to the pharmacological management of heart failure

PURPOSE OF REVIEW

The treatment of acute heart failure is gaining importance, specifically in the perioperative setting. Increasing evidence shows that established forms of therapy using beta-adrenergic inotropic drugs have no effect on long-term survival; thus, anesthetists and intensive care specialists are focusing on new strategies. This review examines, with respect to the literature of the past year, whether these strategies will gain significance in the perioperative setting.

RECENT FINDINGS

Owing to its unique efficacy profile, levosimendan, a calcium sensitizer, improves long-term survival in patients with acute heart failure and has been incorporated into the European Society of Cardiology guidelines. Improved heart function without increased oxygen consumption, anti-ischemic effects, no arrhythmogenic effect and positive effects on intestinal perfusion have been described. Despite the positive effects on hemodynamics and symptoms, tezosentan, an endothelin antagonist, did not improve outcome, perhaps due to too high dosages of the drug. Nesiritide, a recombinant brain natriuretic peptide, may represent an alternative to nitroglycerin and dobutamine and possibly have a benefit for survival. No final conclusions can yet be drawn, however. L-NAME, a nitric oxide synthase antagonist, represents a promising new approach for the treatment of cardiogenic shock. The results must be confirmed in large, randomized studies.

SUMMARY

For perioperative treatment of acute heart failure, levosimendan, nesiritide and L-NAME constitute promising alternatives to conventional inotropic and vasodilatory drugs. The strongest evidence for improving outcome is given for levosimendan. According to the present literature, tezosentan does not currently have any significance for treatment of perioperative heart failure.

Specific enhancement of sarcomeric response to Ca2+protects murine myocardium against ischemia-reperfusion dysfunction

Alteration in myofilament response to Ca2+is a major mechanism for depressed cardiac function after ischemia-reperfusion (I/R) dysfunction. We tested the hypothesis that hearts with increased myofilament response to Ca2+are less susceptible to I/R. In one approach, we studied transgenic (TG) mice with a constitutive increase in myofilament Ca2+sensitivity in which the adult form of cardiac troponin I (cTnI) is stoichiometrically replaced with the embryonic/neonatal isoform, slow skeletal TnI (ssTnI). We also studied mouse hearts with EMD-57033, which acts specifically to enhance myofilament response to Ca2+. We subjected isolated, perfused hearts to an I/R protocol consisting of 25 min of no-flow ischemia followed by 30 min of reperfusion. After I/R, developed pressure and rates of pressure change were significantly depressed and end-diastolic pressure was significantly elevated in nontransgenic (NTG) control hearts. These changes were significantly blunted in TG hearts and in NTG hearts perfused with EMD-57033 during reperfusion, with function returning to nearly baseline levels. Ca2+- and cross bridge-dependent activation, protein breakdown, and phosphorylation in detergent-extracted fiber bundles were also investigated. After I/R NTG fiber bundles exhibited a significant depression of cross bridge-dependent activation and Ca2+-activated tension and length dependence of activation that were not evident in TG preparations. Only NTG hearts demonstrated a significant increase in cTnI phosphorylation. Our results support the hypothesis that specific increases in myofilament Ca2+sensitivity are able to diminish the effect of I/R on cardiac function.

An emerging role for calcium sensitisation in the treatment of heart failure

Heart failure occurs in 2 - 3% of the adult population in the developed world. With decompensation of cardiac function, haemodynamic stability can be achieved by using intravenous vasodilators, diuretics and inotropes. Unlike traditional inotropes, Ca2+ sensitisers enhance cardiac function without significantly increasing cardiac oxygen consumption, promoting arrhythmia or impairing lusitropy. The most promising drug in this new class is levosimendan, which has a unique dual mechanism; it enhances cardiac output through a Ca(2+)-dependent stabilisation of cardiac myofilaments and exhibits vasodilatory effects by opening ATP-dependent K(+) channels. Clinical trials have demonstrated the beneficial haemodynamic effects of levosimendan, and prospective trials are currently underway to confirm its potential benefits on long-term prognosis. Updated guidelines from the European Society of Cardiology advise on how to incorporate levosimendan into care for patients who have acute heart failure.