Effect of levosimendan on myocardial contractility, coronary and peripheral blood flow, and arrhythmias during coronary artery ligation and reperfusion in the in vivo pig model

3D printed micro-scale force gauge arrays to improve human cardiac tissue maturation and enable high throughput drug testing

Human induced pluripotent stem cell - derived cardiomyocytes (iPSC-CMs) are regarded as a promising cell source for establishing in-vitro personalized cardiac tissue models and developing therapeutics. However, analyzing cardiac force and drug response using mature human iPSC-CMs in a high-throughput format still remains a great challenge. Here we describe a rapid light-based 3D printing system for fabricating micro-scale force gauge arrays suitable for 24-well and 96-well plates that enable scalable tissue formation and measurement of cardiac force generation in human iPSC-CMs. We demonstrate consistent tissue band formation around the force gauge pillars with aligned sarcomeres. Among the different maturation treatment protocols we explored, 3D aligned cultures on force gauge arrays with in-culture pacing produced the highest expression of mature cardiac marker genes. We further demonstrated the utility of these micro-tissues to develop significantly increased contractile forces in response to treatment with isoproterenol, levosimendan, and omecamtiv mecarbil. Overall, this new 3D printing system allows for high flexibility in force gauge design and can be optimized to achieve miniaturization and promote cardiac tissue maturation with great potential for high-throughput in-vitro drug screening applications. STATEMENT OF SIGNIFICANCE: The application of iPSC-derived cardiac tissues in translatable drug screening is currently limited by the challenges in forming mature cardiac tissue and analyzing cardiac forces in a high-throughput format. We demonstrate the use of a rapid light-based 3D printing system to build a micro-scale force gauge array that enables scalable cardiac tissue formation from iPSC-CMs and measurement of contractile force development. With the capability to provide great flexibility over force gauge design as well as optimization to achieve miniaturization, our 3D printing system serves as a promising tool to build cardiac tissues for high-throughput in-vitro drug screening applications.

Influence of the coronary circulation on thermal tolerance and cardiac performance during warming in rainbow trout

Thermal tolerance in fish may be related to an oxygen limitation of cardiac function. While the hearts of some fish species receive oxygenated blood via a coronary circulation, the influence of this oxygen supply on thermal tolerance and cardiac performance during warming remain unexplored. Here, we analyzed the effect in vivo of acute warming on coronary blood flow in adult sexually mature rainbow trout ( Onchorhynchus mykiss) and the consequences of chronic coronary ligation on cardiac function and thermal tolerance in juvenile trout. Coronary blood flow at 10°C was higher in females than males (0.56 ± 0.08 vs. 0.30 ± 0.08 ml·min−1·g ventricle−1), and averaged 0.47 ± 0.07 ml·min−1·g ventricle−1 across sexes. Warming increased coronary flow in both sexes until 14°C, at which it peaked and plateaued at 0.78 ± 0.1 and 0.61 ± 0.1 ml·min−1·g ventricle−1 in females and males, respectively. Thus, the scope for increasing coronary flow was 101% in males, but only 39% in females. Coronary-ligated juvenile trout exhibited elevated heart rate across temperatures, reduced Arrhenius breakpoint temperature for heart rate (23.0 vs. 24.6°C), and reduced upper critical thermal maximum (25.3 vs. 26.3°C). To further analyze the effects of coronary flow restriction on cardiac rhythmicity, electrocardiogram characteristics were determined before and after coronary occlusion in anesthetized trout. Occlusion resulted in reduced R-wave amplitude and an elevated S-T segment, indicating myocardial ischemia, while heart rate was unaffected. This suggests that the tachycardia in ligated trout across temperatures in vivo was mainly to compensate for reduced cardiac contractility to maintain cardiac output. Moreover, our findings show that coronary flow increases with warming in a sex-specific manner. This may improve whole animal thermal tolerance, presumably by sustaining cardiac oxygenation and contractility at high temperatures.

Heart calcium sensitizer on morbidity and mortality of high-risk surgical patients with MODS: systematic review and meta-analysis

A total of 440 patients from 10 studies were included in a systematic review to evaluate the association between improved survivals from multiple organ dysfunction syndromes in patients undergoing surgical operation. Health Inter Network Initiatives (HINARI), MEDLINE and EMBASE were searched. Exclusion criteria were duplicate publications, non-human experimental studies, and no mortality data. The primary endpoint was postoperative mortality. Levosimendan was found to be associated with a reduction in postoperative mortality (11/235 [4.7%] in the levosimendan group v 26/205 [12.7%] in the control, odds ratio of 0.35 [0.18-0.71], P for effect as 0.003, P for heterogeneity 0.22, and I(2) as 27.4% (440 patients included), cardiac troponin release, and atrial fibrillation. No difference was found in terms of myocardial infarction, acute renal failure, time on mechanical ventilation, intensive care unit, and hospital stay. Calcium-sensitizer for congestive heart failure; Levosimendan has cardioprotective effects that could result in a reduced operative mortality.

Levosimendan improves contractility in vivo and in vitro in a rodent model of post-myocardial infarction heart failure

AIM

As few studies have presented a thorough analysis of the effect of levosimendan (LEV) on contractility, our purpose was to investigate in vivo cardiac function as well as in vitro cardiomyocyte function and calcium (Ca(2+) ) handling following LEV treatment.

METHODS

Rats with post-myocardial infarction heart failure (HF) induced by ligation of the left anterior descending coronary artery and sham-operated animals were randomized to the infusion of LEV (2.4 μg kg(-1) min(-1) ) or vehicle for 40 min. Echocardiographic examination was coupled to pressure-volume sampling in the left ventricle before (B) and after (40 min) infusion. Isolated left ventricular cardiomyocytes were studied in an epifluorescence microscope.

RESULTS

HF LEV (n = 6), HF vehicle (n = 7), sham LEV (n = 5) and sham vehicle (n = 6) animals were included. LEV infusion compared to vehicle in HF animals reduced left ventricular end-diastolic pressure and mean arterial pressure (both P < 0.001) and improved the slope of the preload-recruitable stroke work (P < 0.05). Administrating LEV to HF cardiomyocytes in vitro improved fractional shortening and Ca(2+) sensitivity index ratio, and increased the diastolic Ca(2+) (all P < 0.01).

CONCLUSION

In HF animals, LEV improved the contractility by increasing the Ca(2+) sensitivity. Furthermore loading conditions were changed, and LEV could consequently change organ perfusion. An observed increase in diastolic Ca(2+) following LEV treatment and clinical implications of this should be further addressed.

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.

Levosimendan decreases intracranial pressure after hypothermic circulatory arrest in a porcine model

OBJECTIVES

Hypothermic circulatory arrest (HCA) provides an optimal operating field in aortic arch surgery, but it is associated with neurological complications. Levosimendan is an inotropic agent with clinical indications for open-heart surgery. Through peripheral vasodilatation, cardiac contractility enhancement and anti-inflammatory function it has a potential to improve cerebral protection after HCA.

DESIGN

Eighteen piglets were randomly assigned to a levosimendan group (n = 9) and a placebo group (n = 9) and underwent a 60-minute period of hypothermic circulatory arrest at 18°C. A levosimendan or placebo infusion (0.2 μg/kg/min) was commenced at the onset of anesthesia and continued for 24 hours. Animals were followed for one week and their neurological recovery was assessed daily. Finally the animals were electively sacrificed and their brain was harvested for histopathological examination.

RESULTS

Levosimendan decreased intracranial pressure during the experiment. There were no differences between the groups in terms of hemodynamic or metabolic data, brain metabolism, neurological recovery or histopathology of the cerebral tissue. In the levosimendan group, cardiac enzymes were slightly more elevated.

CONCLUSIONS

Levosimendan decreased intracranial pressure during the experiment, but in terms of cerebral metabolism, neurological recovery and histopathology of the brain tissue levosimendan did not improve brain protection in this experimental setting.

Ventricular arrhythmias and mortality associated with isoflurane and sevoflurane in a porcine model of myocardial infarction

Ischemia of the myocardium can lead to reversible or irreversible injury depending on the severity and duration of the preceding ischemia. Here we compared sevoflurane and isoflurane with particular reference to their hemodynamic effects and ability to modify the effects of acute severe myocardial ischemia and reperfusion on ventricular arrhythmias and mortality in a porcine model of myocardial infarction. Female Large White pigs were premedicated with ketamine, midazolam, and atropine. Propofol was given intravenously for the anesthetic induction, and anesthesia was maintained with isoflurane or sevoflurane. Endovascular, fluoroscopy-guided, coronary procedures were performed to occlude the midleft anterior descending artery by using a coronary angioplasty balloon. After 75 min, the balloon catheter system was withdrawn and the presence of adequate reperfusion flow was verified. The pigs were followed for 2 mo, and overall mortality rate was calculated. The isoflurane group showed lower arterial pressure throughout the procedure, with the difference reaching statistical significance after induction of myocardial ischemia. The ventricular fibrillation rate was higher in isoflurane group (81.3%) than the sevoflurane group (51.7%; relative risk, 1.57 [1.03 to 2.4]). Overall survival was lower in the isoflurane group (75%) than the sevoflurane group (96.4%). In conclusion, in this porcine model of myocardial ischemia and reperfusion, sevoflurane was associated with higher hemodynamic stability and fewer ventricular arrhythmias and mortality than was isoflurane.

Increased myofilament Ca2+-sensitivity and arrhythmia susceptibility

Increased myofilament Ca(2+) sensitivity is a common attribute of many inherited and acquired cardiomyopathies that are associated with cardiac arrhythmias. Accumulating evidence supports the concept that increased myofilament Ca(2+) sensitivity is an independent risk factor for arrhythmias. This review describes and discusses potential underlying molecular and cellular mechanisms how myofilament Ca(2+) sensitivity affects cardiac excitation and leads to the generation of arrhythmias. Emphasized are downstream effects of increased myofilament Ca(2+) sensitivity: altered Ca(2+) buffering/handling, impaired energy metabolism and increased mechanical stretch, and how they may contribute to arrhythmogenesis.

Levosimendan reduces cardiac troponin release after cardiac surgery: a meta-analysis of randomized controlled studies

OBJECTIVES

The authors performed a meta-analysis to investigate the effects of levosimendan in cardiac surgery. Inotropic drugs have never shown beneficial effects on outcome in randomized controlled studies, with the possible exception of levosimendan.

DESIGN

A meta-analysis.

SETTING

Hospitals.

PARTICIPANTS

A total of 139 patients from 5 randomized controlled studies were included in the analysis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Four investigators independently searched BioMedCentral and PubMed. Inclusion criteria were random allocation to treatment, and comparison of levosimendan versus control performed on cardiac surgery patients. Exclusion criteria were duplicate publications, nonhuman experimental studies, and no outcome data. The endpoint was postoperative cardiac troponin release. Levosimendan was associated with a significant reduction in cardiac troponin peak release (weighted mean difference = 2.5 ng/dL [-3.86, -1.14], p = 0.0003) and in time to hospital discharge (weighted mean difference = -1.38 days [-2.78, 0.03], p = 0.05). No other relevant outcome (mortality, myocardial infarction, atrial fibrillation, time on mechanical ventilation, and intensive care unit stay) was improved in those patients receiving levosimendan.

CONCLUSIONS

Levosimendan has cardioprotective effects, resulting in reduced postoperative cardiac troponin release.

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.

[Role of Levosimendan in intensive care treatment of myocardial insufficiency]

Levosimendan is a calcium sensitizer that is currently in the focus of intensive care medicine because it may be superior to standard inotropic agents in the treatment of acute myocardial insufficiency. The effects of levosimendan mainly depend on three predominant mechanisms: 1) positive inotropic effect by increasing the sensitivity of cardiac myofilaments to calcium ions, 2) vasodilatory effect by stimulation of adenosine triphosphate-sensitive potassium channels and 3) inhibition of phosphodiesterase-III. In a large number of experimental and clinical studies further possible indications for levosimendan have been described, e.g. cardioprotection during ischemia, cardiogenic shock, septic myocardial insufficiency and pulmonary hypertension. This review article critically summarizes the current scientific and clinical knowledge about levosimendan, its pharmacologic characteristics, mechanisms of action as well as indications and potential risks.

Levosimendan improves the initial outcome of cardiopulmonary resuscitation in a swine model of cardiac arrest

BACKGROUND

Cardiac arrest remains the leading cause of death in Western societies. Advanced Life Support guidelines propose epinephrine (adrenaline) for its treatment. The aim of this study was to assess whether a calcium sensitizer agent, such as levosimendan, administered in combination with epinephrine during cardiopulmonary resuscitation, would improve the initial resuscitation success.

METHODS

Ventricular fibrillation was induced in 20 Landrace/Large-White piglets, and left untreated for 8 min. Resuscitation was then attempted with precordial compressions, mechanical ventilation and electrical defibrillation. The animals were randomized into two groups (10 animals each): animals in Group A received saline as placebo (10 ml dilution, bolus) + epinephrine (0.02 mg/kg), and animals in Group B received levosimendan (0.012 mg/kg/10 ml dilution, bolus) + epinephrine (0.02 mg/kg) during cardiopulmonary resuscitation. Electrical defibrillation was attempted after 10 min of ventricular fibrillation.

RESULTS

Four animals in Group A showed restoration of spontaneous circulation and 10 in Group B (P = 0.011). The coronary perfusion pressure, saturation of peripheral oxygenation and brain regional oxygen saturation were significantly higher during cardiopulmonary resuscitation in Group B.

CONCLUSIONS

A calcium sensitizer agent, when administered during cardiopulmonary resuscitation, significantly improves initial resuscitation success and increases coronary perfusion pressure during cardiopulmonary resuscitation.

Effects of levosimendan on myocardial infarct size and hemodynamics in a closed-chest porcine ischemia-reperfusion model

INTRODUCTION

Levosimendan is a positive inotropic drug with vasodilator action and proposed myocardioprotective properties. In a canine model, levosimendan increased coronary collateral flow and reduced myocardial infarct size (IS). We investigated the effect of levosimendan on IS and hemodynamics in the closed-chest porcine ischemia-reperfusion model, which is devoid of coronary collaterals.

METHODS

Infusion with levosimendan (0.2 microg/kg/min following a bolus of 24 microg/kg) or saline was initiated 30 min prior to ischemia in anaesthetized pigs (n = 10 in both groups). Balloon occlusion of the left anterior descending coronary artery for 45 min was followed by 2 1/2 h of reperfusion. Hemodynamics were monitored with a Swan-Ganz catheter and a left ventricular pressure micromanometer. Left ventricular systolic and diastolic function was estimated by dP/dt(max) and tau, respectively. Myocardial area at risk (AAR) and IS were assessed in vivo by myocardial perfusion imaging (MPI) and ex vivo by histopathology (fluorescein staining for AAR, tetrazolium staining for IS).

RESULTS

Prior to ischemia, levosimendan improved left ventricular systolic and diastolic function with coincident preload and afterload reduction. Cardiac output increased by 10 +/- 4% (p = 0.04), dP/dt(max) by 15 +/- 5% (p = 0.01). Pulmonary capillary wedge pressure decreased by 18 +/- 3% (p = 0.04), tau by 11 +/- 2% (p = 0.001), and mean arterial pressure by 11 +/- 2% (p < 0.001). A similar trend was observed during ischemia-reperfusion. The ratio of IS/AAR was not reduced by levosimendan compared to saline as evaluated by histopathology (76 +/- 4% vs. 64 +/- 7%, p = 0.12) and by MPI (94 +/- 2% vs. 87 +/- 5%, p = 0.14).

CONCLUSION

Levosimendan improves hemodynamics but does not reduce IS in an ischemia-reperfusion model without coronary collaterals.

Usage of the T1 effect of an iron oxide contrast agent in an animal model to quantify myocardial blood flow by MRI

BACKGROUND

To present a new method for fully quantitative analysis of myocardial blood flow (MBF) using magnetic resonance imaging. The first pass of an intravascular iron oxide contrast medium can be used to quantify myocardial perfusion. The technique was validated in an animal model using colored microspheres.

MATERIALS AND METHODS

In six pigs, a tracking catheter was positioned in the left anterior descending artery (LAD). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was performed on a 1.5-T scanner using a hybrid gradient-echo/echoplanar imaging (GRE-EPI) sequence. Regional myocardial blood flow (rMBF) was altered by either inducing vasodilatation with adenosine or creating coronary artery obstruction. The T(1) effect of a superparamagnetic iron oxide-based contrast medium (Resovist) administered at a dose of 8 micromol/kg was used. Upslope, time-to-peak and peak intensity were calculated from the signal intensity-time curves and absolute rMBF using the Kety-Schmidt equation; results were compared to those obtained using colored microspheres.

RESULTS

The mean rMBF calculated by MRI was 1.49 (+/-6.91, quartile width) ml/min/g versus 3.21 (+/-1.61) ml/min/g measured by means of microspheres under resting conditions. rMBF increased to a mean of 6.21 (+/-2.83) ml/min/g versus 4.22 (+/-1.70) ml/min/g under adenosine and was reduced to zero flow in total occlusion. Linear regression showed the best correlation for upslope (R=0.714), time-to-peak (R=0.626) and the Kety-Schmidt equation (R=0.584).

CONCLUSIONS

The T(1) effect of an iron oxide-based contrast medium allows determination of rMBF when using the Kety-Schmidt equation. The results are similar to those obtained with the standard of reference, colored micropheres, but not better than the results of the semiquantitative approach.

The use of levosimendan in comparison and in combination with dobutamine in the treatment of decompensated heart failure

Levosimendan is a new calcium sensitizer with inotropic and vasodilatory actions mediated by the sensitization of contractile proteins to calcium, opening of potassium channels and inhibition of phosphodiesterase-3. Its alternative mechanisms of action to those of other traditional inotropes provide a new approach in the management of decompensated heart failure. In contrast to dobutamine, levosimendan does not increase myocardial oxygen demand and, therefore, it is thought to have a lower potential to induce increases in myocardial ischemia and cardiac arrhythmias. The commonly used inotropic agent dobutamine increases myocardial contractility at the expense of increased myocardial oxygen consumption and, therefore, it can result in poor outcomes. Although dobutamine may also have favorable hemodynamic and symptomatic effects, levosimendan has been shown to be superior to dobutamine in increasing cardiac output and decreasing pulmonary capillary wedge pressure in patients with decompensated heart failure. In the presence of concomitant beta-blocker therapy, these favorable effects were present or even more pronounced during treatment with levosimendan, but not dobutamine. However, the mortality benefit of levosimendan observed in earlier trials has not been confirmed in recent, larger clinical trials. A distinct advantage of levosimendan over dobutamine is its prolonged hemodynamic effects, which last for up to 7-9 days. There are more data on the safety of levosimendan in ischemic patients than with any other inotropic drug and, therefore, levosimendan seems to be safe and effective in patients with ischemic heart disease when used at the recommended doses. Despite advances in heart failure therapy, many patients experience clinical deterioration, or do not respond to a single inotropic drug. Increasing evidence suggests the use of levosimendan in combination with dobutamine in patients with decompensated heart failure that is refractory to dobutamine alone.

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.

Levosimendan cardioprotection reduces the metabolic response during temporary regional coronary occlusion in an open chest pig model

BACKGROUND

Inotropic and myocardial anti-ischemic effects have been demonstrated with levosimendan. The comparison of levosimendan started before an ischemia-reperfusion event as compared with levosimendan started during ischemia has not been studied.

METHODS

In anesthetized pigs, a major branch of the circumflex artery was completely occluded for 30 min and then reperfused. The metabolism in the ischemic myocardium and in non-ischemic control myocardium was studied with microdialysis concomitantly with monitoring of global hemodynamics and coronary artery flow in the chosen artery. In the protection group (PRO, n= 6), a levosimendan infusion was started 30 min before coronary artery occlusion, and in the treatment group (TRE, n= 6), a levosimendan infusion was started 10 min after the coronary artery occlusion with a loading dose of 13.3 microg/kg followed by an infusion of 0.67 microg/kg/min. A two-way repeated measures ANOVA completed with Bonferroni's multiple comparison procedure was applied to the data. A P < 0.05 was considered significant.

RESULTS

During the ischemic period, the cardiac output and contractility (dp/dt(max)) were higher in the PRO as compared with the TRE and the systemic vascular resistance was lower. The myocardial microdialysate glucose concentration in the ischemic area during ischemia was higher in the PRO as compared with the TRE, and the lactate/pyruvate ratio and the lactate concentration were lower. The differences in the metabolites persisted into the first 10 min of reperfusion. No differences were found for the non-ischemic areas.

CONCLUSION

Levosimendan used throughout myocardial ischemia-reperfusion might have a cardioprotective affect on the response to myocardial ischemia as compared with levosimendan started during the ischemia.

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.

Preconditioning effects of levosimendan in coronary artery bypass grafting—a pilot study

BACKGROUND

The calcium sensitizer levosimendan protects against myocardial ischaemia and reperfusion injury in animal models.

METHODS

The present pilot study investigated whether a short infusion before coronary artery bypass grafting (CABG) would protect the myocardium and improve postoperative haemodynamics. Twenty-four patients with stable angina undergoing elective CABG surgery were randomized to receive either placebo or levosimendan (24 microg kg(-1)) infused i.v. over a 10 min period just before placing the patient on cardiopulmonary bypass.

RESULTS

Perioperative haemodynamic variables, concentrations of cardiac troponin I over the 48 h postoperative period, and clinical outcomes were assessed. There were no adverse effects related to levosimendan. Compared with control patients, levosimendan-treated patients had lower postoperative troponin I concentrations (P<0.05) and a higher cardiac index (P<0.05).

CONCLUSION

Patients receiving a short infusion of levosimendan before CABG showed evidence of less myocardial damage, suggestive of a preconditioning effect. Larger outcome studies are thus indicated to confirm benefit.

Levosimendan for the treatment of acute heart failure syndromes

Levosimendan is a novel calcium-sensitising agent that has been shown to have beneficial inotropic, metabolic and vasodilatory effects in the treatment of acute and advanced chronic heart failure. Levosimendan binds to troponin-C in cardiomyocytes and, thereby, improves cardiac contractility without disturbing the metabolic status of the heart and increasing myocardial oxygen demand or provoking fatal cardiac arrhythmias. Levosimendan also opens ATP-sensitive potassium channels, causing peripheral arterial and venous dilatation, and increasing coronary flow reserve. When it is given as a short-term therapy, levosimendan enhances cardiac output, reduces systemic vascular resistance and lowers pulmonary capillary wedge pressure. Clinical outcomes were significantly reduced in decompensated or postmyocardial infarction heart failure patients who received levosimendan, compared with those on dobutamine or placebo. Recent investigations focusing on the anti-inflammatory and antiapoptotic actions of levosimendan in the failing heart indicate that improvement of cardiac contractile performance is closely related with the drug-induced reduction of circulating pro-inflammatory cytokines and apoptosis inducers. The most common adverse effects of levosimendan treatment are hypotension and headache. Overall, levosimendan represents an effective and safe option for the treatment of decompensated heart failure patients.

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.

Comparison between dobutamine and levosimendan for management of postresuscitation myocardial dysfunction*

OBJECTIVE

To investigate the effects of levosimendan, a nonadrenergic inotropic calcium sensitizer, in comparison with adrenergic dobutamine for the management of postresuscitation myocardial dysfunction following resuscitation from prolonged cardiac arrest.

DESIGN

Randomized prospective animal study.

SETTING

Animal research laboratory.

SUBJECTS

Male Yorkshire-cross domestic pigs

INTERVENTIONS

Ventricular fibrillation was induced in male domestic pigs weighing between 35 and 40 kg. Cardiopulmonary resuscitation, including precordial compression and mechanical ventilation, was started after 7 mins of untreated cardiac arrest. Electrical defibrillation was attempted after 5 mins of cardiopulmonary resuscitation. Each animal was successfully resuscitated without pharmacologic intervention. Resuscitated animals were randomized to treatment with levosimendan, dobutamine, or saline placebo. The inotropic agents or an equivalent volume of placebo diluents was administered 10 mins after restoration of spontaneous circulation. Levosimendan was administered in a loading dose of 20 microg.kg over 10 mins followed by a 220-min infusion of 0.4 microg.kg.min. Dobutamine was infused into the right atrium in an amount of 5 microg.kg.min. Treatment was continued for a total of 230 mins.

MEASUREMENTS AND MAIN RESULTS

Levosimendan and dobutamine produced comparable increases in cardiac output. However, levosimendan produced significantly greater left ventricular ejection fraction and fractional area changes compared with dobutamine and saline placebo.

CONCLUSIONS

Levosimendan has the potential of improving postresuscitation myocardial function. It is likely to serve as an alternative to dobutamine as an inotropic agent for management of postresuscitation myocardial dysfunction.

Levosimendan, a New Calcium-Sensitizing Inotrope for Heart Failure

Calcium sensitizers are a new class of inotropes that share the in vitro properties of calcium sensitization and phosphodiesterase inhibition. Levosimendan is a distinct calcium sensitizer, as it stabilizes the interaction between calcium and troponin C by binding to troponin C in a calcium-dependent manner, improving inotropy without adversely affecting lusitropy. It does not exhibit clinically relevant phosphodiesterase inhibition at therapeutic concentrations. It also exerts vasodilatory effects, possibly through activation of several potassium channels and other less well characterized mechanisms. The pharmacokinetics of levosimendan are similar in healthy subjects and patients with heart failure and remain relatively unaltered by age, sex, and organ dysfunction. In preclinical and clinical studies, levosimendan exerted potent dose-dependent positive inotropic and vasodilatory activity. Unlike conventional inotropes, levosimendan is not associated with significant increases in myocardial oxygen consumption, proarrhythmia, or neurohormonal activation. The most common adverse effects are attributable to the vasodilation. Two large, double-blind, randomized trials demonstrated favorable hemodynamic effects, improved tolerability, and a possible mortality benefit over dobutamine and placebo in patients who had acute symptoms of failure and required inotropic therapy. The long-term effect on patient outcomes is being confirmed in ongoing placebo- and inotrope-controlled trials. Levosimendan appears to be an effective inodilator devoid of the detrimental effects of conventional inotropes. In the future, levosimendan may provide a promising alternative to conventional inotropes for patients with acutely decompensated heart failure.

Levosimendan: a review of its use in the management of acute decompensated heart failure

Levosimendan (Simdax) is a calcium-sensitising drug that stabilises the troponin molecule in cardiac muscle, thus prolonging its effects on contractile proteins, with concomitant vasodilating properties. Intravenous levosimendan (12-24 microg/kg loading dose followed by 0.1-0.2 microg/kg/min for 24 hours, adjusted for response and tolerability) is approved for the short-term treatment of acute severe decompensated heart failure. Cardiac output increased by about 30% and pulmonary capillary wedge pressure and systemic vascular resistance decreased by about 17-29% in patients with decompensated heart failure receiving intravenous levosimendan. In large, well controlled trials in patients with decompensated heart failure, intravenous levosimendan was significantly more effective than placebo or dobutamine for overall haemodynamic response rate (primary endpoint). Significant benefits were also seen for mortality (versus placebo or dobutamine) and for the combined risk of worsening heart failure or death (versus dobutamine). Improvements in key symptoms (dyspnoea and fatigue) have not been consistently demonstrated. Hospitalisation costs were similar for levosimendan and dobutamine; the total incremental (hospitalisation plus drug) cost per life-year saved (extrapolated to 3 years) for levosimendan relative to dobutamine was estimated at Euro 3205 (year of costing 2000). Levosimendan is generally well tolerated, with an adverse event profile at recommended dosages similar to that in patients receiving placebo. Cardiac rate/rhythm disorders and headache were the most common events. At higher dosages, patients receiving levosimendan had higher rates of sinus tachycardia than those in placebo recipients. More patients receiving dobutamine than those receiving levosimendan experienced angina pectoris/chest pain/myocardial ischaemia or rate/rhythm disorders.

CONCLUSION

Intravenous levosimendan is an effective calcium-sensitising drug with vasodilatory and inotropic effects, and superior efficacy/tolerability to those of intravenous dobutamine in patients with acute decompensated heart failure. It may be associated with reduced mortality compared with both placebo and dobutamine. Levosimendan is generally well tolerated and may have less potential for cardiac rate/rhythm disorders than dobutamine. While evidence from well designed trials confirming the improved mortality over dobutamine and investigating haemodynamic efficacy and mortality versus other positive inotropes is required, intravenous levosimendan appears to be a useful addition to the treatment options for acute decompensated heart failure in patients with low cardiac output.