Nitric oxide for inhalation in ST-elevation myocardial infarction (NOMI): a multicentre, double-blind, randomized controlled trial

The role of blood nitric oxide level in predicting return of spontaneous circulation: a prospective case-control study

OBJECTIVE

The aim of this study was to investigate whether there is a difference in serum nitric oxide levels between patients who return spontaneously after cardiopulmonary resuscitation and those who do not. We also examined the potential of using serum nitric oxide levels as a marker to make an accurate decision about patient survival.

METHODS

We included 100 consecutive patients who were brought to the emergency clinic due to cardiac arrest. Blood samples were taken from these patients at admission, 30 min after admission, and when resuscitation was terminated.

RESULTS

We found that there was a significant difference in NO1 and NO3 values between the group of patients who did not return after cardiopulmonary resuscitation and the group in which spontaneous circulation returned. The NO1 value was significant in the receiver operating characteristic (ROC) analysis, while the NO3 value was not. A higher NO1 value provided a higher rate of survival.

CONCLUSION

Our findings suggest that nitric oxide may be a useful parameter to support the decision about patient survival. A higher NO1 value is associated with a better prognosis and survival rate. Therefore, serum nitric oxide levels may be a suitable indicator to support the decision-making process regarding patient survival.

Inhaled NO at a crossroads in cardiac surgery: current need to improve mechanistic understanding, clinical trial design and scientific evidence

Inhaled nitric oxide (NO) has been used in pediatric and adult perioperative cardiac intensive care for over three decades. NO is a cellular signaling molecule that induces smooth muscle relaxation in the mammalian vasculature. Inhaled NO has the unique ability to exert its vasodilatory effects in the pulmonary vasculature without any hypotensive side-effects in the systemic circulation. In patients undergoing cardiac surgery, NO has been reported in numerous studies to exert beneficial effects on acutely lowering pulmonary artery pressure and reversing right ventricular dysfunction and/or failure. Yet, various investigations failed to demonstrate significant differences in long-term clinical outcomes. The authors, serving as an advisory board of international experts in the field of inhaled NO within pediatric and adult cardiac surgery, will discuss how the existing scientific evidence can be further improved. We will summarize the basic mechanisms underlying the clinical applications of inhaled NO and how this translates into the mandate for inhaled NO in cardiac surgery. We will move on to the popular use of inhaled NO and will talk about the evidence base of the use of this selective pulmonary vasodilator. This review will elucidate what kind of clinical and biological barriers and gaps in knowledge need to be solved and how this has impacted in the development of clinical trials. The authors will elaborate on how the optimization of inhaled NO therapy, the development of biomarkers to identify the target population and the definition of response can improve the design of future large clinical trials. We will explain why it is mandatory to gain an international consensus for the state of the art of NO therapy far beyond this expert advisory board by including the different major players in the field, such as the different medical societies and the pharma industry to improve our understanding of the real-life effects of inhaled NO in large scale observational studies. The design for future innovative randomized controlled trials on inhaled NO therapy in cardiac surgery, adequately powered and based on enhanced biological phenotyping, will be crucial to eventually provide scientific evidence of its clinical efficacy beyond its beneficial hemodynamic properties.

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Blood pressure targets and management during post-cardiac arrest care

Blood pressure is one modifiable physiological target in patients treated in the intensive care unit after cardiac arrest. Current Guidelines recommend targeting a mean arterial pressure (MAP) of higher than 65-70 mmHg using fluid resuscitation and the use of vasopressors. Management strategies will vary based in the setting, i.e. the pre-hospital compared to the in-hospital phase. Epidemiological data suggest that some degree of hypotension requiring vasopressors occur in almost 50% of patients. A higher MAP could theoretically increase coronary blood flow but on the other hand the use of vasopressor may result in an increase in cardiac oxygen demand and arrhythmia. An adequate MAP is paramount for maintaining cerebral blood flow. In some cardiac arrest patients the cerebral autoregulation may be disturbed resulting in the need for higher MAP in order to avoid decreasing cerebral blood flow. Thus far, four studies including little more than 1000 patients have compared a lower and higher MAP target in cardiac arrest patients. The achieved mean difference of MAP between groups has varied from 10-15 mmHg. Based on these studies a Bayesian meta-analysis suggests that the posterior probability that a future study would find treatment effects higher than a 5% difference between groups to be less than 50%. On the other hand, this analysis also suggests, that the likelihood of harm with a higher MAP target is also low. Noteworthy is that all studies to date have focused mainly on patients with a cardiac cause of the arrest with the majority of patients being resuscitated from a shockable initial rhythm. Future studies should aim to include also non-cardiac causes and aim to target a wider separation in MAP between groups.

Rationale and design of the RESTORE trial: A multicenter, randomized, double-blinded, parallel-group, placebo-controlled trial to evaluate the effect of Shenfu injection on myocardial injury in STEMI patients after primary PCI

BACKGROUND

The mortality following ST-segment elevation myocardial infarction (STEMI) remains substantial in the reperfusion era. Shenfu injection, as a traditional Chinese herbal formula, can alleviate ischemia-reperfusion injury through multiple pharmacologic effects. However, no robust data are available regarding the role of Shenfu injection in reducing infarct size for patients with STEMI undergoing primary percutaneous coronary intervention (PPCI).

METHODS/DESIGN

This RESTORE trial is a multicenter, randomized, double-blind, parallel-group, placebo-controlled trial (NCT04493840). A total of 326 eligible patients with first-time anterior STEMI undergoing PPCI within 12 h of symptom onset will be enrolled from 10 centers in mainland China. Patients are randomized in a 1:1 fashion to receive either intravenous Shenfu injection (80mL Shenfu injection + 70mL 5% glucose injection) or placebo group (150mL 5% glucose injection) before reperfusion and followed by once a day until 5 days after PPCI. The primary end point is infarct size assessed by cardiac magnetic resonance (CMR) imaging 5±2 days after PPCI. The major secondary end points include enzymatic infarct size, microvascular obstruction, intramyocardial hemorrhage, left ventricular volume and ejection fraction assessed by CMR, as well as cardiovascular events at 30 days.

CONCLUSIONS

The RESTORE trial is sufficiently powered to demonstrate the clinical effects of Shenfu injection on myocardial injury in STEMI patients undergoing PPCI in the contemporary era.

Pharmacological Cardioprotection against Ischemia Reperfusion Injury-The Search for a Clinical Effective Therapy

Pharmacological conditioning aims to protect the heart from myocardial ischemia-reperfusion injury (IRI). Despite extensive research in this area, today, a significant gap remains between experimental findings and clinical practice. This review provides an update on recent developments in pharmacological conditioning in the experimental setting and summarizes the clinical evidence of these cardioprotective strategies in the perioperative setting. We start describing the crucial cellular processes during ischemia and reperfusion that drive acute IRI through changes in critical compounds (∆G_ATP, Na⁺, Ca²⁺, pH, glycogen, succinate, glucose-6-phosphate, mitoHKII, acylcarnitines, BH₄, and NAD⁺). These compounds all precipitate common end-effector mechanisms of IRI, such as reactive oxygen species (ROS) generation, Ca²⁺ overload, and mitochondrial permeability transition pore opening (mPTP). We further discuss novel promising interventions targeting these processes, with emphasis on cardiomyocytes and the endothelium. The limited translatability from basic research to clinical practice is likely due to the lack of comorbidities, comedications, and peri-operative treatments in preclinical animal models, employing only monotherapy/monointervention, and the use of no-flow (always in preclinical models) versus low-flow ischemia (often in humans). Future research should focus on improved matching between preclinical models and clinical reality, and on aligning multitarget therapy with optimized dosing and timing towards the human condition.

Nitric Oxide in Cardiac Surgery: A Review Article

Perioperative organ injury remains a medical, social and economic problem in cardiac surgery. Patients with postoperative organ dysfunction have increases in morbidity, length of stay, long-term mortality, treatment costs and rehabilitation time. Currently, there are no pharmaceutical technologies or non-pharmacological interventions that can mitigate the continuum of multiple organ dysfunction and improve the outcomes of cardiac surgery. It is essential to identify agents that trigger or mediate an organ-protective phenotype during cardiac surgery. The authors highlight nitric oxide (NO) ability to act as an agent for perioperative protection of organs and tissues, especially in the heart-kidney axis. NO has been delivered in clinical practice at an acceptable cost, and the side effects of its use are known, predictable, reversible and relatively rare. This review presents basic data, physiological research and literature on the clinical application of NO in cardiac surgery. Results support the use of NO as a safe and promising approach in perioperative patient management. Further clinical research is required to define the role of NO as an adjunct therapy that can improve outcomes in cardiac surgery. Clinicians also have to identify cohorts of responders for perioperative NO therapy and the optimal modes for this technology.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Inhaled nitric oxide: role in the pathophysiology of cardio-cerebrovascular and respiratory diseases

Nitric oxide (NO) is a key molecule in the biology of human life. NO is involved in the physiology of organ viability and in the pathophysiology of organ dysfunction, respectively. In this narrative review, we aimed at elucidating the mechanisms behind the role of NO in the respiratory and cardio-cerebrovascular systems, in the presence of a healthy or dysfunctional endothelium. NO is a key player in maintaining multiorgan viability with adequate organ blood perfusion. We report on its physiological endogenous production and effects in the circulation and within the lungs, as well as the pathophysiological implication of its disturbances related to NO depletion and excess. The review covers from preclinical information about endogenous NO produced by nitric oxide synthase (NOS) to the potential therapeutic role of exogenous NO (inhaled nitric oxide, iNO). Moreover, the importance of NO in several clinical conditions in critically ill patients such as hypoxemia, pulmonary hypertension, hemolysis, cerebrovascular events and ischemia-reperfusion syndrome is evaluated in preclinical and clinical settings. Accordingly, the mechanism behind the beneficial iNO treatment in hypoxemia and pulmonary hypertension is investigated. Furthermore, investigating the pathophysiology of brain injury, cardiopulmonary bypass, and red blood cell and artificial hemoglobin transfusion provides a focus on the potential role of NO as a protective molecule in multiorgan dysfunction. Finally, the preclinical toxicology of iNO and the antimicrobial role of NO-including its recent investigation on its role against the Sars-CoV2 infection during the COVID-19 pandemic-are described.

Therapeutic Gases and Inhaled Anesthetics as Adjunctive Therapies in Critically Ill Patients

The administration of exogenous oxygen to support adequate gas exchange is the cornerstone of respiratory care. In the past few years, other gaseous molecules have been introduced in clinical practice to treat the wide variety of physiological derangement seen in critical care patients.Inhaled nitric oxide (NO) is used for its unique selective pulmonary vasodilator effect. Recent studies showed that NO plays a pivotal role in regulating ischemia-reperfusion injury and it has antibacterial and antiviral activity.Helium, due to its low density, is used in patients with upper airway obstruction and lower airway obstruction to facilitate gas flow and to reduce work of breathing.Carbon monoxide (CO) is a poisonous gas that acts as a signaling molecule involved in many biologic pathways. CO's anti-inflammatory and antiproliferative effects are under investigation in the setting of acute respiratory distress and idiopathic pulmonary fibrosis.Inhaled anesthetics are widely used in the operative room setting and, with the development of anesthetic reflectors, are now a valid option for sedation management in the intensive care unit.Many other gases such as xenon, argon, and hydrogen sulfide are under investigation for their neuroprotective and cardioprotective effects in post-cardiac arrest syndrome.With all these therapeutic options available, the clinician must have a clear understanding of the physiologic basis, therapeutic potential, and possible adverse events of these therapeutic gases. In this review, we will present the therapeutic gases other than oxygen used in clinical practice and we will describe other promising therapeutic gases that are in the early phases of investigation.

Therapeutic Targets for Regulating Oxidative Damage Induced by Ischemia-Reperfusion Injury: A Study from a Pharmacological Perspective

Ischemia-reperfusion (I-R) injury is damage caused by restoring blood flow into ischemic tissues or organs. This complex and characteristic lesion accelerates cell death induced by signaling pathways such as apoptosis, necrosis, and even ferroptosis. In addition to the direct association between I-R and the release of reactive oxygen species and reactive nitrogen species, it is involved in developing mitochondrial oxidative damage. Thus, its mechanism plays a critical role via reactive species scavenging, calcium overload modulation, electron transport chain blocking, mitochondrial permeability transition pore activation, or noncoding RNA transcription. Other receptors and molecules reduce tissue and organ damage caused by this pathology and other related diseases. These molecular targets have been gradually discovered and have essential roles in I-R resolution. Therefore, the current study is aimed at highlighting the importance of these discoveries. In this review, we inquire about the oxidative damage receptors that are relevant to reducing the damage induced by oxidative stress associated with I-R. Several complications on surgical techniques and pathology interventions do not mitigate the damage caused by I-R. Nevertheless, these therapies developed using alternative targets could work as coadjuvants in tissue transplants or I-R-related pathologies

Role of Nitric Oxide and Protein S-Nitrosylation in Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a process in which damage is induced in hypoxic tissue when oxygen supply is resumed after ischemia. During IRI, restoration of reduced nitric oxide (NO) levels may alleviate reperfusion injury in ischemic organs. The protective mechanism of NO is due to anti-inflammatory effects, antioxidant effects, and the regulation of cell signaling pathways. On the other hand, it is generally known that S-nitrosylation (SNO) mediates the detrimental or protective effect of NO depending on the action of the nitrosylated target protein, and this is also applied in the IRI process. In this review, the effect of each change of NO and SNO during the IRI process was investigated.

Pharmacologic Prevention of Myocardial Ischemia-Reperfusion Injury in Patients With Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention

ABSTRACT

Establishing efficient perfusion into the myocardium is the main purpose in patients with acute coronary syndrome, but the process of reperfusion is not without risk and can damage the myocardium paradoxically. Unfortunately, there is no effective treatment for reperfusion injury, and efforts to find an efficient preventive approach are still ongoing. In the past 3 decades, there have been many successful animal studies on how to prevent reperfusion injury; nonetheless, translation to the clinical setting has almost always proven disappointing. In this article, we review clinical studies on the prevention of reperfusion injury in patients with acute coronary syndrome undergoing primary percutaneous coronary intervention in a pharmacologic-based approach. We categorize all the agents that are evaluated for the prevention of myocardial reperfusion injury based on their mechanisms of action into 5 groups: drugs that can reduce oxidative stress, drugs that can affect cellular metabolism, rheological agents that target microvascular obstruction, anti-inflammatory agents, and agents with mixed mechanisms of action. Then, review all the clinical studies of these agents in the setting of primary percutaneous coronary intervention. Finally, we will discuss the possible reasons for the failure in translation of studies into practice and propose potential solutions to overcome this problem.

Nitrite and myocardial ischaemia reperfusion injury. Where are we now?

Cardiovascular disease remains the leading cause of death worldwide despite major advances in technology and treatment, with coronary heart disease (CHD) being a key contributor. Following an acute myocardial infarction (AMI), it is imperative that blood flow is rapidly restored to the ischaemic myocardium. However, this restoration is associated with an increased risk of additional complications and further cardiomyocyte death, termed myocardial ischaemia reperfusion injury (IRI). Endogenously produced nitric oxide (NO) plays an important role in protecting the myocardium from IRI. It is well established that NO mediates many of its downstream functions through the 'canonical' NO-sGC-cGMP pathway, which is vital for cardiovascular homeostasis; however, this pathway can become impaired in the face of inadequate delivery of necessary substrates, in particular L-arginine, oxygen and reducing equivalents. Recently, it has been shown that during conditions of ischaemia an alternative pathway for NO generation exists, which has become known as the 'nitrate-nitrite-NO pathway'. This pathway has been reported to improve endothelial dysfunction, protect against myocardial IRI and attenuate infarct size in various experimental models. Furthermore, emerging evidence suggests that nitrite itself provides multi-faceted protection, in an NO-independent fashion, against a myriad of pathophysiologies attributed to IRI. In this review, we explore the existing pre-clinical and clinical evidence for the role of nitrate and nitrite in cardioprotection and discuss the lessons learnt from the clinical trials for nitrite as a perconditioning agent. We also discuss the potential future for nitrite as a pre-conditioning intervention in man.

Clinical application of nitric oxide in ischemia and reperfusion injury: A literature review

Ischemia–reperfusion injury (IRI) is a series of multifactorial cellular events that lead to increased cellular dysfunction after the restoration of oxygen delivery to hypoxic tissue, which can result in acute heart failure and cerebral dysfunction. This injury is severe and would lead to significant morbidity and mortality and poses an important therapeutic challenge for physicians. Nitric oxide (NO) minimizes the deleterious effects of IRI on cells. NO donors, such as organic nitrates and sodium nitroprusside, are used systematically to treat heart failure, angina, and pulmonary hypertension. Inhaled NO gas was approved by the FDA in 1999 to treat hypoxic newborns, and its beneficial ameliorations reach outside the realm of lung disease. This review will summarize the clinical application of NO in IRI.

Optimum Blood Pressure in Patients With Shock After Acute Myocardial Infarction and Cardiac Arrest

BACKGROUND

In patients with shock after acute myocardial infarction (AMI), the optimal level of pharmacologic support is unknown. Whereas higher doses may increase myocardial oxygen consumption and induce arrhythmias, diastolic hypotension may reduce coronary perfusion and increase infarct size.

OBJECTIVES

This study aimed to determine the optimal mean arterial pressure (MAP) in patients with AMI and shock after cardiac arrest.

METHODS

This study used patient-level pooled analysis of post-cardiac arrest patients with shock after AMI randomized in the Neuroprotect (Neuroprotective Goal Directed Hemodynamic Optimization in Post-cardiac Arrest Patients; NCT02541591) and COMACARE (Carbon Dioxide, Oxygen and Mean Arterial Pressure After Cardiac Arrest and Resuscitation; NCT02698917) trials who were randomized to MAP 65 mm Hg or MAP 80/85 to 100 mm Hg targets during the first 36 h after admission. The primary endpoint was the area under the 72-h high-sensitivity troponin-T curve.

RESULTS

Of 235 patients originally randomized, 120 patients had AMI with shock. Patients assigned to the higher MAP target (n = 58) received higher doses of norepinephrine (p = 0.004) and dobutamine (p = 0.01) and reached higher MAPs (86 ± 9 mm Hg vs. 72 ± 10 mm Hg, p < 0.001). Whereas admission hemodynamics and angiographic findings were all well-balanced and revascularization was performed equally effective, the area under the 72-h high-sensitivity troponin-T curve was lower in patients assigned to the higher MAP target (median: 1.14 μg.72 h/l [interquartile range: 0.35 to 2.31 μg.72 h/l] vs. median: 1.56 μg.72 h/l [interquartile range: 0.61 to 4.72 μg. 72 h/l]; p = 0.04). Additional pharmacologic support did not increase the risk of a new cardiac arrest (p = 0.88) or atrial fibrillation (p = 0.94). Survival with good neurologic outcome at 180 days was not different between both groups (64% vs. 53%, odds ratio: 1.55; 95% confidence interval: 0.74 to 3.22).

CONCLUSIONS

In post-cardiac arrest patients with shock after AMI, targeting MAP between 80/85 and 100 mm Hg with additional use of inotropes and vasopressors was associated with smaller myocardial injury.

Perioperative Cardioprotection: Clinical Implications

Perioperative cardioprotection aims to minimize the consequences of myocardial ischemia-reperfusion injury. In isolated tissue and animal experiments, several treatments have been identified providing cardioprotection. Some of these strategies have been confirmed in clinical proof-of-concept studies. However, the final translation of cardioprotective strategies to really improve clinical outcome has been disappointing: large randomized controlled clinical trials mostly revealed inconclusive, neutral, or negative results. This review provides an overview of the currently available evidence regarding clinical implications of perioperative cardioprotective therapies from an anesthesiological perspective, highlighting nonpharmacological as well as pharmacological strategies. We discuss reasons why translation of promising experimental results into clinical practice and outcome improvement is hampered by potential confounders and suggest future perspectives to overcome these limitations.

Co-morbidities and co-medications as confounders of cardioprotection-Does it matter in the clinical setting?

The translation of cardioprotection from robust experimental evidence to beneficial clinical outcome for patients suffering acute myocardial infarction or undergoing cardiovascular surgery has been largely disappointing. The present review attempts to critically analyse the evidence for confounders of cardioprotection in patients with acute myocardial infarction and in patients undergoing cardiovascular surgery. One reason that has been proposed to be responsible for such lack of translation is the confounding of cardioprotection by co-morbidities and co-medications. Whereas there is solid experimental evidence for such confounding of cardioprotection by single co-morbidities and co-medications, the clinical evidence from retrospective analyses of the limited number of clinical data is less robust. The best evidence for interference of co-medications is that for platelet inhibitors to recruit cardioprotection per se and thus limit the potential for further protection from myocardial infarction and for propofol anaesthesia to negate the protection from remote ischaemic conditioning in cardiovascular surgery. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Targeting myocardial ischaemic injury in the absence of reperfusion

Sudden myocardial ischaemia causes an acute coronary syndrome. In the case of ST-elevation myocardial infarction (STEMI), this is usually caused by the acute rupture of atherosclerotic plaque and obstruction of a coronary artery. Timely restoration of blood flow can reduce infarct size, but ischaemic regions of myocardium remain in up to two-thirds of patients due to microvascular obstruction (MVO). Experimentally, cardioprotective strategies can limit infarct size, but these are primarily intended to target reperfusion injury. Here, we address the question of whether it is possible to specifically prevent ischaemic injury, for example in models of chronic coronary artery occlusion. Two main types of intervention are identified: those that preserve ATP levels by reducing myocardial oxygen consumption, (e.g. hypothermia; cardiac unloading; a reduction in heart rate or contractility; or ischaemic preconditioning), and those that increase myocardial oxygen/blood supply (e.g. collateral vessel dilation). An important consideration in these studies is the method used to assess infarct size, which is not straightforward in the absence of reperfusion. After several hours, most of the ischaemic area is likely to become infarcted, unless it is supplied by pre-formed collateral vessels. Therefore, therapies that stimulate the formation of new collaterals can potentially limit injury during subsequent exposure to ischaemia. After a prolonged period of ischaemia, the heart undergoes a remodelling process. Interventions, such as those targeting inflammation, may prevent adverse remodelling. Finally, harnessing of the endogenous process of myocardial regeneration has the potential to restore cardiomyocytes lost during infarction.

Peripheral Blood RNAs and Left Ventricular Dysfunction after Myocardial Infarction: Towards Translation into Clinical Practice

The treatment and early outcome of patients with acute myocardial infarction (MI) have dramatically improved the past decades, but the incidence of left ventricular (LV) dysfunction post-MI remains high. Peripheral blood RNAs reflect pathophysiological changes during acute MI and the inflammatory process. Therefore, these RNAs are promising new markers to molecularly phenotype patients and improve the early identification of patients at risk of subsequent LV dysfunction. We here discuss the coding and long non-coding RNAs that can be measured in peripheral blood of patients with acute MI and list the advantages and limitations for implementation in clinical practice. Although some studies provide preliminary evidence of their diagnostic and prognostic potential, the use of these makers has not yet been implemented in clinical practice. The added value of RNAs to improve treatment and outcome remains to be determined in larger clinical studies. International consortia are now catalyzing renewed efforts to investigate novel RNAs that may improve post-MI outcome in a precision-medicine approach. Graphical Abstract Peripheral blood RNAs reflect the inflammatory changes in acute MI. A number of studies provide preliminary evidence of their prognostic potential, although the use of these makers has not yet been assessed in clinical practice.

Novel Findings and Therapeutic Targets on Cardioprotection of Ischemia/ Reperfusion Injury in STEMI

Acute ST-segment elevation myocardial infarction (STEMI) remains a leading cause of morbidity and mortality around the world. A large number of STEMI patients after the infarction gradually develop heart failure due to the infarcted myocardium. Timely reperfusion is essential to salvage ischemic myocardium from the infarction, but the restoration of coronary blood flow in the infarct-related artery itself induces myocardial injury and cardiomyocyte death, known as ischemia/reperfusion injury (IRI). The factors contributing to IRI in STEMI are complex, and microvascular obstruction, inflammation, release of reactive oxygen species, myocardial stunning, and activation of myocardial cell death are involved. Therefore, additional cardioprotection is required to prevent the heart from IRI. Although many mechanical conditioning procedures and pharmacological agents have been identified as effective cardioprotective approaches in animal studies, their translation into the clinical practice has been relatively disappointing due to a variety of reasons. With new emerging data on cardioprotection in STEMI over the past few years, it is mandatory to reevaluate the effectiveness of "old" cardioprotective interventions and highlight the novel therapeutic targets and new treatment strategies of cardioprotection.

Peripheral Blood RNA Levels of QSOX1 and PLBD1 Are New Independent Predictors of Left Ventricular Dysfunction After Acute Myocardial Infarction

BACKGROUND

The identification of patients with acute myocardial infarction (MI) at risk of subsequent left ventricular (LV) dysfunction remains challenging, but it is important to optimize therapies. The aim of this study was to determine the unbiased RNA profile in peripheral blood of patients with acute MI and to identify and validate new prognostic markers of LV dysfunction.

METHODS

We prospectively enrolled a discovery cohort with acute MI (n=143) and performed whole-blood RNA profiling at different time points. We then selected transcripts on admission that related to LV dysfunction at follow-up and validated them by quantitative polymerase chain reaction in the discovery cohort, in an external validation cohort (n=449), and in a representative porcine MI model with cardiac magnetic resonance-based measurements of infarct size and postmortem myocardial pathology (n=33).

RESULTS

RNA profiling in the discovery cohort showed upregulation of genes involved in chemotaxis, IL (interleukin)-6, and NF-κB (nuclear factor-κB) signaling in the acute phase of MI. Expression levels of the majority of these transcripts paralleled the rise in cardiac troponin T and decayed at 30 days. RNA levels of QSOX1, PLBD1, and S100A8 on admission with MI correlated with LV dysfunction at follow-up. Using quantitative polymerase chain reaction, we confirmed that QSOX1 and PLBD1 predicted LV dysfunction (odds ratio, 2.6 [95% CI, 1.1-6.1] and 3.2 [95% CI, 1.4-7.4]), whereas S100A8 did not. In the external validation cohort, we confirmed QSOX1 and PLBD1 as new independent markers of LV dysfunction (odds ratio, 1.41 [95% CI, 1.06-1.88] and 1.43 [95% CI, 1.08-1.89]). QSOX1 had an incremental predictive value in a model consisting of clinical variables and cardiac biomarkers (including NT-proBNP [N-terminal pro-B-type natriuretic peptide]). In the porcine MI model, whole-blood levels of QSOX1 and PLBD1 related to neutrophil infiltration in the ischemic myocardium in an infarct size-independent manner.

CONCLUSIONS

Peripheral blood QSOX1 and PLBD1 in acute MI are new independent markers of LV dysfunction post-MI.

Editor's Choice- Pathophysiology and therapy of myocardial ischaemia/reperfusion syndrome

There is a need to find interventions able to reduce the extent of injury in reperfused ST-segment elevation myocardial infarction (STEMI) beyond timely reperfusion. In this review, we summarise the clinical impact of STEMI from epidemiological, clinical and biological perspectives. We also revise the pathophysiology underlying the ischaemia/reperfusion syndrome occurring in reperfused STEMI, including the several players involved in this syndrome, such as cardiomyocytes, microcirculation and circulating cells. Interventions aimed to reduce the resultant infarct size, known as cardioprotective therapies, are extensively discussed, putting the focus on both mechanical interventions (i.e. ischaemic conditioning) and promising pharmacological therapies, such as early intravenous metoprolol, exenatide and other glucose modulators, N-acetylcysteine as well as on some other classic therapies which have failed to be translated to the clinical arena. Novel targets for evolving therapeutic interventions to ameliorate ischaemia/reperfusion injury are also discussed. Finally, we highlight the necessity to improve the study design of future randomised clinical trials in the field, as well as to select patients better who can most likely benefit from cardioprotective interventions.

Clofibrate Treatment Decreases Inflammation and Reverses Myocardial Infarction-Induced Remodelation in a Rodent Experimental Model

Myocardial infarction (MI) initiates an inflammatory response that promotes both beneficial and deleterious effects. The early response helps the myocardium to remove damaged tissue; however, a prolonged later response brings cardiac remodeling characterized by functional, metabolic, and structural pathological changes. Current pharmacological treatments have failed to reverse ischemic-induced cardiac damage. Therefore, our aim was to study if clofibrate treatment was capable of decreasing inflammation and apoptosis, and reverse ventricular remodeling and MI-induced functional damage. Male Wistar rats were assigned to (1) Sham coronary artery ligation (Sham) or (2) Coronary artery ligation (MI). Seven days post-MI, animals were further divided to receive vehicle (V) or clofibrate (100 mg/kg, C) for 7 days. The expression of IL-6, TNF-α, and inflammatory related molecules ICAM-1, VCAM-1, MMP-2 and -9, nuclear NF-kB, and iNOS, were elevated in MI-V. These inflammatory biomarkers decreased in MI-C. Also, apoptotic proteins (Bax and pBad) were elevated in MI-V, while clofibrate augmented anti-apoptotic proteins (Bcl-2 and 14-3-3ε). Clofibrate also protected MI-induced changes in ultra-structure. The ex vivo evaluation of myocardial functioning showed that left ventricular pressure and mechanical work decreased in infarcted rats; clofibrate treatment raised those parameters to control values. Echocardiogram showed that clofibrate partially reduced LV dilation. In conclusion, clofibrate decreases cardiac remodeling, decreases inflammatory molecules, and partly preserves myocardial diameters.

Inhaled nitric oxide

Nitric oxide (NO) is a gas that induces relaxation of smooth muscle cells in the vasculature. Because NO reacts with oxyhaemoglobin with high affinity, the gas is rapidly scavenged by oxyhaemoglobin in red blood cells and the vasodilating effects of inhaled NO are limited to ventilated regions in the lung. NO therefore has the unique ability to induce pulmonary vasodilatation specifically in the portions of the lung with adequate ventilation, thereby improving oxygenation of blood and decreasing intrapulmonary right to left shunting. Inhaled NO is used to treat a spectrum of cardiopulmonary conditions, including pulmonary hypertension in children and adults. However, the widespread use of inhaled NO is limited by logistical and financial barriers. We have designed, developed and tested a simple and economic NO generation device, which uses pulsed electrical discharges in air to produce therapeutic levels of NO that can be used for inhalation therapy. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

Pharmacological preconditioning with inhaled nitric oxide (NO): Organ-specific differences in the lifetime of blood and tissue NO metabolites

BACKGROUND

Endogenous nitric oxide (NO) may contribute to ischemic and anesthetic preconditioning while exogenous NO protects against ischemia-reperfusion (I/R) injury in the heart and other organs. Why those beneficial effects observed in animal models do not always translate into clinical effectiveness remains unclear. To mitigate reperfusion damage a source of NO is required. NO inhalation is known to increase tissue NO metabolites, but little information exists about the lifetime of these species. We therefore sought to investigate the fate of major NO metabolite classes following NO inhalation in mice in vivo.

METHODS

C57BL/6J mice were exposed to 80 ppm NO for 1 h. NO metabolites were measured in blood (plasma and erythrocytes) and tissues (heart, liver, lung, kidney and brain) immediately after NO exposure and up to 48 h thereafter. Concentrations of S-nitrosothiols, N-nitrosamines and NO-heme products as well as nitrite and nitrate were quantified by gas-phase chemiluminescence and ion chromatography. In separate experiments, mice breathed 80 ppm NO for 1 h prior to cardiac I/R injury (induced by coronary arterial ligation for 1 h, followed by recovery). After sacrifice, the size of the myocardial infarction (MI) and the area at risk (AAR) were measured.

RESULTS

After NO inhalation, elevated nitroso/nitrosyl levels returned to baseline over the next 24 h, with distinct multi-phasic decay profiles in each compartment. S/N-nitroso compounds and NO-hemoglobin in blood decreased exponentially, but remained above baseline for up to 30min, whereas nitrate was elevated for up to 3hrs after discontinuing NO breathing. Hepatic S/N-nitroso species concentrations remained steady for 30min before dropping exponentially. Nitrate only rose in blood, liver and kidney; nitrite tended to be lower in all organs immediately after NO inhalation but fluctuated considerably in concentration thereafter. NO inhalation before myocardial ischemia decreased the ratio of MI/AAR by 30% vs controls (p = 0.002); only cardiac S-nitrosothiols and NO-hemes were elevated at time of reperfusion onset.

CONCLUSIONS

Metabolites in blood do not reflect NO metabolite status of any organ. Although NO is rapidly inactivated by hemoglobin-mediated oxidation in the circulation, long-lived tissue metabolites may account for the myocardial preconditioning effects of inhaled NO. NO inhalation may afford similar protection in other organs.