The cardioprotection granted by metoprolol is restricted to its administration prior to coronary reperfusion

β-blockers and metabolic modulation: unraveling the complex interplay with glucose metabolism, inflammation and oxidative stress

The growing burden of metabolic disorders manifested by hypertension, type 2 diabetes mellitus, hyperlipidemia, obesity and non-alcoholic fatty liver disease presents a significant global health challenge by contributing to cardiovascular diseases and high mortality rates. Β-blockers are among the most widely used drugs in the treatment of hypertension and acute cardiovascular events. In addition to blocking the receptor sites for catecholamines, third-generation β-blockers with associated vasodilating properties, such as carvedilol and nebivolol, provide a broad spectrum of metabolic effects, including anti-inflammatory and antioxidant properties and a favorable impact on glucose and lipid metabolism. This review aims to report the impact of β-blockers on metabolic modulation based on available literature data. We present an overview of β-blockers and their pleiotropic properties, discuss mechanisms by which these drugs affect cellular metabolism and outline the future perspectives. The influence of β-blockers on glucose metabolism, insulin sensitivity, inflammation and oxidative stress is complex and varies depending on the specific β-blocker used, patient population and underlying health conditions. Recent evidence particularly highlights the potential role of vasodilatory and nitric oxide-mediated properties of nebivolol and carvedilol in improving glycemic control, insulin sensitivity, and lipid metabolism and mitigating oxidative stress and inflammation. It suggests that these drugs may be potential therapeutic options for patients with metabolic disorders, extending beyond their primary role in cardiovascular management.

PD-L1 and AKT Overexpressing Adipose-Derived Mesenchymal Stem Cells Enhance Myocardial Protection by Upregulating CD25+ T Cells in Acute Myocardial Infarction Rat Model

This study explores the synergistic impact of Programmed Death Ligand 1 (PD-L1) and Protein Kinase B (Akt) overexpression in adipose-derived mesenchymal stem cells (AdMSCs) for ameliorating cardiac dysfunction after myocardial infarction (MI). Post-MI adult Wistar rats were allocated into four groups: sham, MI, ADMSC treatment, and ADMSCs overexpressed with PD-L1 and Akt (AdMSC-PDL1-Akt) treatment. MI was induced via left anterior descending coronary artery ligation, followed by intramyocardial AdMSC injections. Over four weeks, cardiac functionality and structural integrity were assessed using pressure-volume analysis, infarct size measurement, and immunohistochemistry. AdMSC-PDL1-Akt exhibited enhanced resistance to reactive oxygen species (ROS) in vitro and ameliorated MI-induced contractile dysfunction in vivo by improving the end-systolic pressure-volume relationship and preload-recruitable stroke work, together with attenuating infarct size. Molecular analyses revealed substantial mitigation in caspase3 and nuclear factor-κB upregulation in MI hearts within the AdMSC-PDL1-Akt group. Mechanistically, AdMSC-PDL1-Akt fostered the differentiation of normal T cells into CD25+ regulatory T cells in vitro, aligning with in vivo upregulation of CD25 in AdMSC-PDL1-Akt-treated rats. Collectively, PD-L1 and Akt overexpression in AdMSCs bolsters resistance to ROS-mediated apoptosis in vitro and enhances myocardial protective efficacy against MI-induced dysfunction, potentially via T-cell modulation, underscoring a promising therapeutic strategy for myocardial ischemic injuries.

No robust reduction of infarct size and no-reflow by metoprolol pretreatment in adult Göttingen minipigs

Whereas prior experiments in juvenile pigs had reported infarct size reduction by intravenous metoprolol early during myocardial ischaemia, two major clinical trials in patients with reperfused acute myocardial infarction were equivocal. We, therefore, went back and tested the translational robustness of infarct size reduction by metoprolol in minipigs. Using a power analysis-based prospective design, we pretreated 20 anaesthetised adult Göttingen minipigs with 1 mg kg-1 metoprolol or placebo and subjected them to 60-min coronary occlusion and 180-min reperfusion. Primary endpoint was infarct size (triphenyl tetrazolium chloride staining) as a fraction of area at risk; no-reflow area (thioflavin-S staining) was a secondary endpoint. There was no significant reduction in infarct size (46 ± 8% of area at risk with metoprolol vs. 42 ± 8% with placebo) or area of no-reflow (19 ± 21% of infarct size with metoprolol vs. 15 ± 23% with placebo). However, the inverse relationship between infarct size and ischaemic regional myocardial blood flow was modestly, but significantly shifted downwards with metoprolol, whereas ischaemic blood flow tended to be reduced by metoprolol. With an additional dose of 1 mg kg-1 metoprolol after 30-min ischaemia in 4 additional pigs, infarct size was also not reduced (54 ± 9% vs. 46 ± 8% in 3 contemporary placebo, n.s.), and area of no-reflow tended to be increased (59 ± 20% vs. 29 ± 12%, n.s.).Infarct size reduction by metoprolol in pigs is not robust, and this result reflects the equivocal clinical trials. The lack of infarct size reduction may be the result of opposite effects of reduced infarct size at any given blood flow and reduced blood flow, possibly through unopposed alpha-adrenergic coronary vasoconstriction.

Cardioprotective Effects of a Selective c-Jun N-terminal Kinase Inhibitor in a Rat Model of Myocardial Infarction

Activation of c-Jun N-terminal kinases (JNKs) is involved in myocardial injury, left ventricular remodeling (LV), and heart failure (HF) after myocardial infarction (MI). The aim of this research was to evaluate the effects of a selective JNK inhibitor, 11H-indeno [1,2-b]quinoxalin-11-one oxime (IQ-1), on myocardial injury and acute myocardial ischemia/reperfusion (I/R) in adult male Wistar rats. Intraperitoneal administration of IQ-1 (25 mg/kg daily for 5 days) resulted in a significant decrease in myocardial infarct size on day 5 after MI. On day 60 after MI, a significant (2.6-fold) decrease in LV scar size, a 2.2-fold decrease in the size of the LV cavity, a 2.9-fold decrease in the area of mature connective tissue, and a 1.7-fold decrease in connective tissue in the interventricular septum were observed compared with the control group. The improved contractile function of the heart resulted in a significant (33%) increase in stroke size, a 40% increase in cardiac output, a 12% increase in LV systolic pressure, a 28% increase in the LV maximum rate of pressure rise, a 45% increase in the LV maximum rate of pressure drop, a 29% increase in the contractility index, a 14% increase in aortic pressure, a 2.7-fold decrease in LV end-diastolic pressure, and a 4.2-fold decrease in LV minimum pressure. We conclude that IQ-1 has cardioprotective activity and reduces the severity of HF after MI.

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.

Neutrophils in aging and aging‐related pathologies

Over the past millennia, life expectancy has drastically increased. While a mere 25 years during Bronze and Iron ages, life expectancy in many European countries and in Japan is currently above 80 years. Such an increase in life expectancy is a result of improved diet, life style, and medical care. Yet, increased life span and aging also represent the most important non-modifiable risk factors for several pathologies including cardiovascular disease, neurodegenerative diseases, and cancer. In recent years, neutrophils have been implicated in all of these pathologies. Hence, this review provides an overview of how aging impacts neutrophil production and function and conversely how neutrophils drive aging-associated pathologies. Finally, we provide a perspective on how processes of neutrophil-driven pathologies in the context of aging can be targeted therapeutically.

Early donepezil monotherapy or combination with metoprolol significantly prevents subsequent chronic heart failure in rats with reperfused myocardial infarction

Despite the presence of clinical guidelines recommending that β-blocker treatment be initiated early after reperfused myocardial infarction (RMI), acute myocardial infarction remains a leading cause of chronic heart failure (CHF). In this study, we compared the effects of donepezil, metoprolol, and their combination on the progression of cardiac remodeling in rats with RMI. The animals were randomly assigned to untreated (UT), donepezil-treated (DT), metoprolol-treated (MT), and a combination of donepezil and metoprolol (DMT) groups. On day 8 after surgery, compared to the UT, the DT and DMT significantly improved myocardial salvage, owing to the suppression of macrophage infiltration and apoptosis. After the 10-week treatment, the DT and DMT exhibited decreased heart rate, reduced myocardial infarct size, attenuated cardiac dysfunction, and decreased plasma levels of brain natriuretic peptide and catecholamine, thereby preventing subsequent CHF. These results suggest that donepezil monotherapy or combined therapy with β-blocker may be an alternative pharmacotherapy post-RMI.

No sex-related differences in infarct size, no-reflow and protection by ischaemic preconditioning in Göttingen minipigs

Aims

Female sex has been proposed to be cardioprotective per se. Studies with myocardial ischaemia/reperfusion and infarct size as endpoint have demonstrated cardioprotection in female, castrated male and male pigs. These studies are difficult to compare, given the different pig strains, models, durations of ischaemia and methods of infarct size quantification. The few studies using both female and male pigs reported no differences in infarct size and cardioprotection. We therefore prospectively compared infarct size in Göttingen minipigs undergoing ischaemia/reperfusion (I/R) without and with ischaemic preconditioning (IPC) between female, castrated male and male pigs.

Methods and Results

In a prospective, randomised approach, 28 Göttingen open-chest, anaesthetised minipigs underwent 60 min ischaemia by distal left anterior descending artery (LAD) occlusion and 180 min reperfusion without and with IPC by 3 cycles of 5 min LAD occlusion/10 min reperfusion. Infarct size with I/R was not different between female, castrated male and male pigs (45±8 vs. 45±13 vs. 41±9% area at risk), as was the reduction in infarct size with IPC (25±11 vs. 30±8 vs. 19±10% area at risk). Also, the area of no-reflow was not different between female, castrated male and male pigs with I/R (57±13 vs. 35±7 vs. 47±26% infarct size) or IPC (4±10 vs.12±20 vs. 0±0% infarct size). Phosphorylation of signal transducer and activator of transcription 3 was increased at 10 min reperfusion by IPC but not by I/R to the same extent in female, castrated male and male pigs (198±30 vs. 230±165 vs. 179±107% of baseline).

Conclusion

Our data do not support the notion of sex- or castration-related differences in infarct size, coronary microvascular injury and cardioprotection by ischaemic preconditioning.

Translational perspective

The translation of successful preclinical studies on cardioprotection to the benefit of patients with reperfused myocardial infarction has been difficult. The difficulties have been attributed to confounders such as co-morbidities and co-medications which patients typically have but animals don´t, but also to age and sex. Notably, female sex has been considered as protective per se. We have now, using our established and clinically relevant pig model of reperfused acute myocardial infarction and ischaemic preconditioning as the most robust cardioprotective intervention looked for sex-related differences of infarct size, no-reflow and cardioprotection by ischaemic preconditioning in a prospectively powered approach but found none such difference.

Complementary Pharmacotherapy for STEMI Undergoing Primary PCI: An Evidence-Based Clinical Approach

Antithrombotic therapy is the cornerstone of pharmacological treatment in patients undergoing primary percutaneous coronary intervention (PCI). However, the acute management of ST elevation myocardial infarction (STEMI) patients includes therapy for pain relief and potential additional strategies for cardioprotection. The safety and efficacy of some commonly used treatments have been questioned by recent evidence. Indeed a concern about morphine use is the interaction between opioids and oral P2Y₁₂ inhibitors; early beta-blocker treatment has shown conflicting results for the improvement of clinical outcomes; and supplemental oxygen therapy lacks benefit in patients without hypoxia and may be of potential harm. Other additional strategies remain disappointing; however, some treatments may be selectively used. Therefore, we intend to present a critical updated review of complementary pharmacotherapy for a modern treatment approach for STEMI patients undergoing primary PCI.

Effects of Metoprolol on Periprocedural Myocardial Infarction After Percutaneous Coronary Intervention (Type 4a MI): An Inverse Probability of Treatment Weighting Analysis

Background: Metoprolol is the most used cardiac selective β-blocker and has been recommended as a mainstay drug in the management of acute myocardial infarction (AMI). However, the evidence supporting this regimen in periprocedural myocardial infarction (PMI) is limited.

Methods: This study identified 860 individuals who suffered PMI following percutaneous coronary intervention (PCI) procedure and median followed up for 3.2 years. Subjects were dichotomized according to whether they received chronic oral sustained-release metoprolol succinate following PMI. After inverse probability of treatment weighting (IPTW) adjustment, logistic regression analysis, Kaplan-Meier curve, and Cox regression analysis were performed to estimate the effects of metoprolol on major adverse cardiovascular events (MACEs) which composed of cardiac death, myocardial infarction (MI), stroke, and revascularization. Moreover, an exploratory analysis was performed according to hypertension, cardiac troponin I (cTnI) elevation, and cardiac function. A double robust adjustment was used for sensitivity analysis.

Results: Among enrolled PMI subjects, 456 (53%) patients received metoprolol treatment and 404 (47%) patients received observation. After IPTW adjustment, receiving metoprolol was found to reduce the subsequent 3-year risk of MACEs by nearly 7.1% [15 vs. 22.1%, absolute risk difference (ARD) = 0.07, number needed to treat (NNT) = 14, relative risk (RR) = 0.682]. In IPTW-adjusted Cox regression analyses, receiving metoprolol was related to a reduced risk of MACEs (hazard ratio [HR] = 0.588, 95%CI [0.385–0.898], P = 0.014) and revascularization (HR = 0.538, 95%CI [0.326–0.89], P = 0.016). Additionally, IPTW-adjusted logistic regression analysis showed that receiving metoprolol reduced the risk of MI at the third year (odds ratio [OR] = 0.972, 95% CI [0.948–997], P = 0.029). Exploratory analysis showed that the protective effect of metoprolol was more pronounced in subgroups of hypertension and cTnI elevation ≥1,000%, and was remained in patients without cardiac dysfunction. The benefits above were consistent when double robust adjustments were performed.

Conclusion: In the real-world setting, receiving metoprolol treatment following PCI-related PMI has decreased the subsequent risk of MACEs, particularly the risk of recurrent MI and revascularization.

Pseudosterins A-C, Three 1-Ethyl-3-formyl-β-carbolines from Pseudostellaria heterophylla and Their Cardioprotective Effects

Pseudostellaria heterophylla is used in China not only as a functional food but also as an herb to tonify the spleen, enhance immunity, and treat palpitation. Our previous investigation showed that a fraction enriched in glycosides obtained from the roots of P. heterophylla possessed pronounced protective effects on H9c2 cells against CoCl₂-induced hypoxic injury. However, the active compounds responsible for the observed effects were still unknown. In the current investigation, pseudosterins A–C (1–3), three new alkaloids with a 1-ethyl-3-formyl-β-carboline skeleton, together with polydatin, have been isolated from the active fraction. Their structures were elucidated on the basis of spectroscopic analysis and quantum chemical calculations. The four compounds showed cardioprotective effects against sodium hydrosulfite-induced hypoxia-reoxygenation injury in H9c2 cells, with the three alkaloids being more potent. This is also the first report of alkaloids with a β-carboline skeleton isolated from P. heterophylla as cardioprotective agents.

Metoprolol combined with nicorandil on unstable angina pectoris can reduce incidence of cardiovascular events and inflammatory reactions

OBJECTIVE

This research was designed to investigate the efficacy of metoprolol combined with nicorandil on unstable angina pectoris (UAP).

METHODS

Totally 174 UAP patients treated in the Laixi City People's Hospital from May 2017 to December 2019 were taken as the research objects. They were divided into the control (n=79, CG) and joint (n=95) groups (JG). Patients in the CG were treated with metoprolol, while those in the JG were treated with nicorandil. The clinical efficacy, adverse events and inflammatory reactions were observed.

RESULTS

The effective rate of the JG was better than that of the CG after treatment. There were no additional adverse reactions, and the incidence of cardiovascular events reduced. The changes of cardiac function manifested that the left ventricular end systolic diameter (LVESD) and left ventricular end diastolic diameter (LVEDD) in the JG were lower than those in the CG, while the left ventricular ejection fraction (LVEF) was higher. In addition, the serum levels of total cholesterol (TC), triglyceride (TG), high-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL-6) in the JG were lower than those in the CG.

CONCLUSION

Metoprolol combined with nicorandil is effective for UAP patients, which reduces the incidence of cardiovascular adverse events and inhibits inflammatory reactions.

Beta-blocker effect on ST-segment: a prespecified analysis of the EARLY-BAMI randomised trial

Objective

The effect of early intravenous (IV) beta-blockers (BBs) administration in patients undergoing primary percutaneous coronary intervention (pPCI) on ST-segment deviation is unknown. We undertook a prespecified secondary analysis of the Early Beta-blocker Administration before primary PCI in patients with ST-elevation Myocardial Infarction (EARLY-BAMI) trial to investigate the effect of early IV BB on ST-segment deviation.

Methods

The EARLY-BAMI trial randomised patients with ST-elevation myocardial infarction (STEMI) to IV metoprolol (2×5 mg bolus) or matched placebo before pPCI. The prespecified outcome, evaluated by an independent core laboratory blinded to study treatment, was the residual ST-segment deviation 1 hour after pPCI (ie, the percentage of patients with >3 mm cumulative ST deviation at 1 hour after pPCI).

Results

An ECG for the evaluation of residual ST-segment deviation 1 hour after pPCI was available in 442 out of 683 randomised patients. The BB group had a lower heart rate after pPCI compared with placebo (71.2±13.2 vs 74.3±13.6, p=0.016); however, no differences were noted in the percentages of patients with >3 mm cumulative ST deviation at 1 hour after pPCI (58.6% vs 54.1%, p=0.38, in BB vs placebo, respectively) neither a significant difference was found for the percentages of patients in each of the four prespecified groups (normalised ST-segment; 1–3 mm; 4–6 mm;>6 mm residual ST-deviation).

Conclusions

In patients with STEMI, who were being transported for primary PCI, early IV BB administration did not significantly affect ST-segment deviation after pPCI compared with placebo. The neutral result of early IV BB administration on an early marker of pharmacological effect is consistent with the absence of subsequent improvement of clinical outcomes.

Metoprolol exerts a non-class effect against ischaemia-reperfusion injury by abrogating exacerbated inflammation

Aims

Clinical guidelines recommend early intravenous β-blockers during ongoing myocardial infarction; however, it is unknown whether all β-blockers exert a similar cardioprotective effect. We experimentally compared three clinically approved intravenous β-blockers.

Methods and results

Mice undergoing 45 min/24 h ischaemia–reperfusion (I/R) received vehicle, metoprolol, atenolol, or propranolol at min 35. The effect on neutrophil infiltration was tested in three models of exacerbated inflammation. Neutrophil migration was evaluated in vitro and in vivo by intravital microscopy. The effect of β-blockers on the conformation of the β1 adrenergic receptor was studied in silico. Of the tested β-blockers, only metoprolol ameliorated I/R injury [infarct size (IS) = 18.0% ± 0.03% for metoprolol vs. 35.9% ± 0.03% for vehicle; P < 0.01]. Atenolol and propranolol had no effect on IS. In the three exacerbated inflammation models, neutrophil infiltration was significantly attenuated only in the presence of metoprolol (60%, 50%, and 70% reductions vs. vehicle in myocardial I/R injury, thioglycolate-induced peritonitis, and lipopolysaccharide-induced acute lung injury, respectively). Migration studies confirmed the particular ability of metoprolol to disrupt neutrophil dynamics. In silico analysis indicated different intracellular β1 adrenergic receptor conformational changes when bound to metoprolol than to the other two β-blockers.

Conclusions

Metoprolol exerts a disruptive action on neutrophil dynamics during exacerbated inflammation, resulting in an infarct-limiting effect not observed with atenolol or propranolol. The differential effect of β-blockers may be related to distinct conformational changes in the β1 adrenergic receptor upon metoprolol binding. If these data are confirmed in a clinical trial, metoprolol should become the intravenous β-blocker of choice for patients with ongoing infarction.

Intravenous Statin Administration During Myocardial Infarction Compared With Oral Post-Infarct Administration

BACKGROUND

Beyond lipid-lowering, statins exert cardioprotective effects. High-dose statin treatment seems to reduce cardiovascular complications in high-risk patients. The ideal timing and administration regime remain unknown.

OBJECTIVES

This study compared the cardioprotective effects of intravenous statin administration during myocardial infarction (MI) with oral administration immediately post-MI.

METHODS

Hypercholesterolemic pigs underwent MI induction (90 min of ischemia) and were kept for 42 days. Animals were distributed in 3 arms (A): A1 received an intravenous bolus of atorvastatin during MI; A2 received an intravenous bolus of vehicle during MI; and A3 received oral atorvastatin within 2 h post-MI. A1 and A3 remained on daily oral atorvastatin for the following 42 days. Cardiac magnetic resonance analysis (days 3 and 42 post-MI) and molecular/histological studies were performed.

RESULTS

At day 3, A1 showed a 10% reduction in infarct size compared with A3 and A2 and a 50% increase in myocardial salvage. At day 42, both A1 and A3 showed a significant decrease in scar size versus A2; however, A1 showed a further 24% reduction versus A3. Functional analyses revealed improved systolic performance in A1 compared with A2 and less wall motion abnormalities in the jeopardized myocardium versus both groups at day 42. A1 showed enhanced collagen content and AMP-activated protein kinase activation in the scar, increased vessel density in the penumbra, higher tumor necrosis factor α plasma levels and lower peripheral blood mononuclear cell activation versus both groups.

CONCLUSIONS

Intravenous administration of atorvastatin during MI limits cardiac damage, improves cardiac function, and mitigates remodeling to a larger extent than when administered orally shortly after reperfusion. This therapeutic approach deserves to be investigated in ST-segment elevation MI patients.

Neutrophil-Mediated Cardiac Damage After Acute Myocardial Infarction: Significance of Defining a New Target Cell Type for Developing Cardioprotective Drugs

Significance: Acute myocardial infarction (AMI) is a leading cause of death worldwide. Post-AMI survival rates have increased with the introduction of angioplasty as a primary coronary intervention. However, reperfusion after angioplasty represents a clinical paradox, restoring blood flow to the ischemic myocardium while simultaneously inducing ion and metabolic imbalances that stimulate immune cell recruitment and activation, mitochondrial dysfunction and damaging oxidant production. Recent Advances: Preclinical data indicate that these metabolic imbalances contribute to subsequent heart failure through sustaining local recruitment of inflammatory leukocytes and oxidative stress, cardiomyocyte death, and coronary microvascular disturbances, which enhance adverse cardiac remodeling. Both left ventricular dysfunction and heart failure are strongly linked to inflammation and immune cell recruitment to the damaged myocardium. Critical Issues: Overall, therapeutic anti-inflammatory and antioxidant agents identified in preclinical trials have failed in clinical trials. Future Directions: The versatile neutrophil-derived heme enzyme, myeloperoxidase (MPO), is gaining attention as an important oxidative mediator of reperfusion injury, vascular dysfunction, adverse ventricular remodeling, and atrial fibrillation. Accordingly, there is interest in therapeutically targeting neutrophils and MPO activity in the setting of heart failure. Herein, we discuss the role of post-AMI inflammation linked to myocardial damage and heart failure, describe previous trials targeting inflammation and oxidative stress post-AMI, highlight the potential adverse impact of neutrophil and MPO, and detail therapeutic options available to target MPO clinically in AMI patients.

P2Y12 antagonists and cardiac repair post-myocardial infarction: global and regional heart function analysis and molecular assessments in pigs

Aims

P2Y12 antagonists are the standard in antiplatelet therapy but their potential effects on functional myocardial recovery and cardioprotection post-myocardial infarction (MI) are unknown. We investigated in a preclinical model of MI whether ticagrelor and clopidogrel differently affect cardiac repair post-MI.

Methods and results

Pigs either received: (i) clopidogrel (600 mg; 75 mg/qd); (ii) ticagrelor (180 mg; 90 mg/bid); and (iii) placebo control. MI was induced by mid-left anterior descending coronary artery balloon occlusion (60 min) and animals received the maintenance doses for the following 42 days. Serial cardiac magnetic resonance was performed at Day 3 and Day 42 for the assessment of global and regional cardiac parameters. We determined cardiac AMP-activated protein kinase (AMPK), Akt/PKB, aquaporin-4, vascular density, and fibrosis. In comparison to controls, both P2Y12 antagonists limited infarct expansion at Day 3, although ticagrelor induced a further 5% reduction (P < 0.05 vs. clopidogrel) whereas oedema was only reduced by ticagrelor (≈23% P < 0.05). Scar size decreased at Day 42 in ticagrelor-treated pigs vs. controls but not in clopidogrel-treated pigs. Left ventricular ejection fraction was higher 3 days post-MI in ticagrelor-treated pigs and persisted up to Day 42 (P < 0.05 vs. post-MI). Regional analysis revealed that control and clopidogrel-treated pigs had severe and extensive wall motion abnormalities in the jeopardized myocardium and a reduced myocardial viability that was not as evident in ticagrelor-treated pigs (χ2P < 0.05 vs. ticagrelor). Only ticagrelor enhanced myocardial AMPK and Akt/PKB activation and reduced aquaporin-4 levels (P < 0.05 vs. control and clopidogrel). No differences were observed in vessel density and fibrosis markers among groups.

Conclusions

Ticagrelor is more efficient than clopidogrel in attenuating myocardial structural and functional alterations post-MI and in improving cardiac healing. These benefits are associated with persistent AMPK and Akt/PKB activation.

Antiapoptotic Effect of β1 Blockers in Ascending Thoracic Aortic Smooth Muscle Cells: The Role of HSP70 Expression

Heat shock proteins (HSPs) play an important role in the cellular adaptation to stress, a requisite for cell survival. The aortic wall appears to be a target for increased expression of HSPs during surgical stress. We aimed to define the expression and function of aortic HSP70 in 31 patients with normal ascending thoracic aortic diameter who underwent aortic valve replacement due to aortic valve stenosis and in 35 patients with dilated ascending thoracic aorta who underwent replacement of an ascending thoracic aortic aneurysm. To elucidate responsible signaling mechanisms we used an in vitro model of rat hypoxic aortic vascular smooth muscle cell (AVSMC) cultures. We demonstrated an increase in AVSMC HSP70 and an attenuation of the apoptotic markers (TUNEL-positive nuclei, caspase-3 activity, Bax/Bcl2 ratio) in aortic wall tissue specimens from both aortic valve stenosis and ascending thoracic aortic aneurysm patients on β1 blockade with metoprolol. In vitro, metoprolol treatment of hypoxic rat AVSMCs increased nitric oxide (NO) production, induced heat shock factor 1 transport to the nucleus, upregulated HSP70, decreased p53 phosphorylation and attenuated apoptosis. Blockade of NO production, resulted in decreased HSP70 and prevented the metoprolol-induced anti-apoptotic response of hypoxic AVSMCs. We demonstrate an anti-apoptotic effect of metoprolol dependent on NO-induced HSP70 expression, and thus augmentation of HSP70 expression should be considered as a therapeutic approach to limit apoptosis in the human ascending thoracic aorta of patients undergoing cardiac surgery.

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.

Stimulation of the Beta2 Adrenergic Receptor at Reperfusion Limits Myocardial Reperfusion Injury via an Interleukin-10-Dependent Anti-Inflammatory Pathway in the Spleen

BACKGROUND

In addition to the airway-relaxing effects, β2 adrenergic receptor (β2AR) agonists are also found to have broad anti-inflammatory effects. The current study was conducted to define the role of β2AR agonists in limiting myocardial ischemia/reperfusion injury (IRI).

METHODS AND RESULTS

Adult male wild-type (WT) and interleukin (IL)-10 knockout (KO) mice underwent a 40-min left coronary artery ligation and 60-min reperfusion. A selective β2AR agonist, Clenbuterol, at doses of 0.1 μg or 1 μg/g weight i.v. 5 min before reperfusion, significantly reduced myocardial infarct size (IS) by 28% and 39% (vs. control, P<0.05) in WT mice respectively, but had no protective effect in IL-10 KO mice. Inhalational therapy with nebulized Clenbuterol, Albuterol, Salmeterol or Arformoterol immediately before ischemia significantly reduced IS (P<0.05) in WT mice. Splenectomy similarly reduced IS as Clenbuterol-treated mice, but intravenous Clenbuterol did not further reduce IS in splenectomized mice. In splenectomized WT mice, acute transfer of isolated splenocytes, not the Clenbuterol-pretreated splenocytes, restored the myocardial IS to the level of intact mice. Intravenous Clenbuterol significantly increased splenic protein levels of β2AR, phosphorylated Akt and IL-10 and plasma IL-10, and inhibited the expression of pro-inflammatory mRNAs.

CONCLUSIONS

Both intravenous and inhalational β2AR agonists exert a cardioprotective effect against IRI by activating the anti-inflammatory β2AR-IL-10 pathway.

Ischaemic preconditioning - Current knowledge and potential future applications after 30 years of experience

Ischaemic preconditioning (IPC) phenomenon has been known for thirty years. During that time several studies showed that IPC provided by brief ischaemic and reperfusion episodes prior to longer ischaemia can bestow a protective effect to both preconditioned and also remote organs. IPC affecting remote organs is called remote ischaemic preconditioning. Initially, most IPC studies were focused on enhancing myocardial resistance to subsequent ischaemia and reperfusion injury. However, preconditioning was found to be a universal phenomenon and was observed in various organs and tissues including the heart, liver, brain, retina, kidney, skeletal muscles and intestine. Currently, there are a lot of simultaneous studies are underway aiming at finding out whether IPC can be helpful in protecting these organs. The mechanism of local and remote IPC is complex and not well known. Several triggers, intracellular pathways and effectors, humoral, neural and induced by genetic changes may be considered potential pathways in the protective activity of local and remote IPC. Local and remote IPC mechanism may potentially serve as heart protection during cardiac surgery and may limit the infarct size of the myocardium, can be a strategy for preventing the development of acute kidney injury development and liver damage during transplantation, may protect the brain against ischaemic injury. In addition, the method is safe, non-invasive, cheap and easily applicable. The main purpose of this review article is to present new advances which would help to understand the potential mechanism of IPC. It also discusses both its potential applications and utility in clinical settings.

Neutrophil stunning by metoprolol reduces infarct size

The β1-adrenergic-receptor (ADRB1) antagonist metoprolol reduces infarct size in acute myocardial infarction (AMI) patients. The prevailing view has been that metoprolol acts mainly on cardiomyocytes. Here, we demonstrate that metoprolol reduces reperfusion injury by targeting the haematopoietic compartment. Metoprolol inhibits neutrophil migration in an ADRB1-dependent manner. Metoprolol acts during early phases of neutrophil recruitment by impairing structural and functional rearrangements needed for productive engagement of circulating platelets, resulting in erratic intravascular dynamics and blunted inflammation. Depletion of neutrophils, ablation of Adrb1 in haematopoietic cells, or blockade of PSGL-1, the receptor involved in neutrophil-platelet interactions, fully abrogated metoprolol's infarct-limiting effects. The association between neutrophil count and microvascular obstruction is abolished in metoprolol-treated AMI patients. Metoprolol inhibits neutrophil-platelet interactions in AMI patients by targeting neutrophils. Identification of the relevant role of ADRB1 in haematopoietic cells during acute injury and the protective role upon its modulation offers potential for developing new therapeutic strategies.

Protective approaches against myocardial ischemia reperfusion injury

Myocardial ischemia-reperfusion is the leading cause for the events of cardiovascular disease, and is considered as a major contributor to the morbidity and mortality associated with coronary occlusion. The myocardial damage caused by ischemia-reperfusion injury constitutes the primary pathological manifestation of coronary artery disease. It results from the interaction between the substances that accumulate during ischemia and those that are delivered on reperfusion. The level of this damage can range from a small insult resulting in limited myocardial damage to a large injury culminating in myocyte death. Importantly, major ischemia-reperfusion injury to the heart can result in permanent disability or death. Given the worldwide prevalence of coronary artery disease, developing a strategy to provide cardioprotection against ischemia-reperfusion-induced damage is of great importance. Currently, the treatment of reperfusion injury following ischemia is primarily supportive, since no specific target-oriented therapy has been validated thus far. Nevertheless, therapeutic approaches to protect against myocardial ischemia-reperfusion injury remain an active area of investigation given the detrimental effects of this phenomenon.

Impact of the Timing of Metoprolol Administration During STEMI on Infarct Size and Ventricular Function

BACKGROUND

Pre-reperfusion administration of intravenous (IV) metoprolol reduces infarct size in ST-segment elevation myocardial infarction (STEMI).

OBJECTIVES

This study sought to determine how this cardioprotective effect is influenced by the timing of metoprolol therapy having either a long or short metoprolol bolus-to-reperfusion interval.

METHODS

We performed a post hoc analysis of the METOCARD-CNIC (effect of METOprolol of CARDioproteCtioN during an acute myocardial InfarCtion) trial, which randomized anterior STEMI patients to IV metoprolol or control before mechanical reperfusion. Treated patients were divided into short- and long-interval groups, split by the median time from 15 mg metoprolol bolus to reperfusion. We also performed a controlled validation study in 51 pigs subjected to 45 min ischemia/reperfusion. Pigs were allocated to IV metoprolol with a long (-25 min) or short (-5 min) pre-perfusion interval, IV metoprolol post-reperfusion (+60 min), or IV vehicle. Cardiac magnetic resonance (CMR) was performed in the acute and chronic phases in both clinical and experimental settings.

RESULTS

For 218 patients (105 receiving IV metoprolol), the median time from 15 mg metoprolol bolus to reperfusion was 53 min. Compared with patients in the short-interval group, those with longer metoprolol exposure had smaller infarcts (22.9 g vs. 28.1 g; p = 0.06) and higher left ventricular ejection fraction (LVEF) (48.3% vs. 43.9%; p = 0.019) on day 5 CMR. These differences occurred despite total ischemic time being significantly longer in the long-interval group (214 min vs. 160 min; p < 0.001). There was no between-group difference in the time from symptom onset to metoprolol bolus. In the animal study, the long-interval group (IV metoprolol 25 min before reperfusion) had the smallest infarcts (day 7 CMR) and highest long-term LVEF (day 45 CMR).

CONCLUSIONS

In anterior STEMI patients undergoing primary angioplasty, the sooner IV metoprolol is administered in the course of infarction, the smaller the infarct and the higher the LVEF. These hypothesis-generating clinical data are supported by a dedicated experimental large animal study.

The no-reflow phenomenon: State of the art

Primary percutaneous coronary intervention (PCI) is the best available reperfusion strategy for acute ST-segment elevation myocardial infarction (STEMI), with nearly 95% of occluded coronary vessels being reopened in this setting. Despite re-establishing epicardial coronary vessel patency, primary PCI may fail to restore optimal myocardial reperfusion within the myocardial tissue, a failure at the microvascular level known as no-reflow (NR). NR has been reported to occur in up to 60% of STEMI patients with optimal coronary vessel reperfusion. When it does occur, it significantly attenuates the beneficial effect of reperfusion therapy, leading to poor outcomes. The pathophysiology of NR is complex and incompletely understood. Many phenomena are known to contribute to NR, including leukocyte infiltration, vasoconstriction, activation of inflammatory pathways and cellular oedema. Vascular damage and haemorrhage may also play important roles in the establishment of NR. In this review, we describe the pathophysiological mechanisms of NR and the tools available for diagnosing it. We also describe the microvasculature and the endothelial mechanisms involved in NR, which may provide relevant therapeutic targets for reducing NR and improving the prognosis for patients.

Impact of left ventricular hypertrophy on troponin release during acute myocardial infarction: new insights from a comprehensive translational study

BACKGROUND

Biomarkers are frequently used to estimate infarct size (IS) as an endpoint in experimental and clinical studies. Here, we prospectively studied the impact of left ventricular (LV) hypertrophy (LVH) on biomarker release in clinical and experimental myocardial infarction (MI).

METHODS AND RESULTS

ST-segment elevation myocardial infarction (STEMI) patients (n=140) were monitored for total creatine kinase (CK) and cardiac troponin I (cTnI) over 72 hours postinfarction and were examined by cardiac magnetic resonance (CMR) at 1 week and 6 months postinfarction. MI was generated in pigs with induced LVH (n=10) and in sham-operated pigs (n=8), and serial total CK and cTnI measurements were performed and CMR scans conducted at 7 days postinfarction. Regression analysis was used to study the influence of LVH on total CK and cTnI release and IS estimated by CMR (gold standard). Receiver operating characteristic (ROC) curve analysis was performed to study the discriminatory capacity of the area under the curve (AUC) of cTnI and total CK in predicting LV dysfunction. Cardiomyocyte cTnI expression was quantified in myocardial sections from LVH and sham-operated pigs. In both the clinical and experimental studies, LVH was associated with significantly higher peak and AUC of cTnI, but not with differences in total CK. ROC curves showed that the discriminatory capacity of AUC of cTnI to predict LV dysfunction was significantly worse for patients with LVH. LVH did not affect the capacity of total CK to estimate IS or LV dysfunction. Immunofluorescence analysis revealed significantly higher cTnI content in hypertrophic cardiomyocytes.

CONCLUSIONS

Peak and AUC of cTnI both significantly overestimate IS in the presence of LVH, owing to the higher troponin content per cardiomyocyte. In the setting of LVH, cTnI release during STEMI poorly predicts postinfarction LV dysfunction. LV mass should be taken into consideration when IS or LV function are estimated by troponin release.

Esmolol added in repeated, cold, oxygenated blood cardioplegia improves myocardial function after cardiopulmonary bypass

OBJECTIVE

This study investigated if the β-receptor blocking agent esmolol, added to standard oxygenated blood cardioplegia, improved myocardial function after weaning from bypass.

DESIGN

A block-randomized, blinded study.

SETTING

A university laboratory.

PARTICIPANTS

Twenty anesthetized pigs, Norwegian Landrace.

INTERVENTIONS

After cardiopulmonary bypass, cardiac arrest was induced with cold (12°C), oxygenated blood cardioplegia, enriched with either esmolol or vehicle, repeated every 20 minutes. After 100 minutes the heart was reperfused and weaned.

MEASUREMENTS AND MAIN RESULTS

Left ventricular function was evaluated with pressure-volume loops, local myocardial function with multilayer strain and strain rate by epicardial short-axis tissue Doppler imaging. One hour after declamping, preload recruitable stroke work did not differ between groups, but increased to 72±3 mmHg in esmolol-treated animals v 57±4 mmHg (p<0.001) in controls after 3 hours. Radial peak ejection strain rate also was increased by esmolol; 6.0±1.0 s(-1)v 2.9±0.3 s(-1) (p<0.001) in subendocardium and 3.9±0.5 s(-1)v 2.3±0.2 s(-1) (p<0.005) in the midmyocardium. Cardiac index was increased, 4.0±0.2 L/min/m(2) by esmolol v 3.3±0.1 L/min/m(2) for controls (p<0.05). Isovolumetric relaxation time constant was reduced by esmolol, 23±1 ms v 26±1 ms (p<0.025). Troponin-T did not differ and was 339±48 ng/L for the esmolol group and 357±55 ng/L for the control group (p = 0.81).

CONCLUSIONS

Esmolol added to blood cardioplegia preserved systolic cardiac function during the first 3 hours after reperfusion in a porcine model with 100 minutes of cardioplegic arrest.

Rationale and design of a double-blind, multicenter, randomized, placebo-controlled clinical trial of early administration of intravenous β-blockers in patients with ST-elevation myocardial infarction before primary percutaneous coronary intervention: EARLY β-blocker administration before primary PCI in patients with ST-elevation myocardial infarction trial

BACKGROUND

β-Blockers have a class 1a recommendation in the treatment of patients with ST-elevation myocardial infarctions (STEMIs), as they are associated with a reduced mortality, recurrent myocardial infarction, life-threatening arrhythmias, and with prevention of unfavorable left ventricular remodeling. Whether early administration before primary percutaneous coronary intervention (PCI) of intravenous β-blockers reduces the infarct size in the current era is unknown.

HYPOTHESIS

We postulate that the early administration of β-blockers will reduce the myocardial infarcted area as assessed by magnetic resonance imaging (MRI) at 30 days.

DESIGN

In a multinational, multicenter, double-blind, placebo-controlled, randomized trial, patients with symptoms and signs of STEMI and transferred to a hospital for primary PCI will be randomized in a 1:1 fashion to intravenous metoprolol (5 mg twice daily) administration or placebo. Before admission, study treatment will be started as soon as possible after the diagnosis of STEMI. After admission, primary PCI will be performed as per standard of care. After primary PCI, medical treatment will occur as per current guidelines in all patients, including the use of oral β-blockers. The primary end point is the myocardial infarct size as assessed by MRI at 30 days. Based on a superiority design and assuming an 18% relative infarct size reduction (from 28% to 23.5%), 408 patients are required to be enrolled, accounting for 20% drop-out (α = .05 and power = 80%).

SUMMARY

The EARLY-BAMI trial is a multinational, multicenter, double-blind, placebo-controlled, randomized clinical trial that will investigate the impact of intravenous metoprolol administration before primary PCI for STEMI on myocardial infarct size as measured with MRI at 30 days.

ESC working group cellular biology of the heart: position paper: improving the preclinical assessment of novel cardioprotective therapies

Ischaemic heart disease (IHD) remains the leading cause of death and disability worldwide. As a result, novel therapies are still needed to protect the heart from the detrimental effects of acute ischaemia–reperfusion injury, in order to improve clinical outcomes in IHD patients. In this regard, although a large number of novel cardioprotective therapies discovered in the research laboratory have been investigated in the clinical setting, only a few of these have been demonstrated to improve clinical outcomes. One potential reason for this lack of success may have been the failure to thoroughly assess the cardioprotective efficacy of these novel therapies in suitably designed preclinical experimental animal models. Therefore, the aim of this Position Paper by the European Society of Cardiology Working Group Cellular Biology of the Heart is to provide recommendations for improving the preclinical assessment of novel cardioprotective therapies discovered in the research laboratory, with the aim of increasing the likelihood of success in translating these new treatments into improved clinical outcomes.

Top 10 cardiovascular therapies and interventions for the next decade

Cardiovascular disease (CVD) has become the most-common cause of death worldwide. The Western lifestyle does not promote healthy living, and the consequences are most devastating when social inequalities are combined with economic factors and population growth. The expansion of poor nutritional habits, obesity, and associated conditions (such as diabetes mellitus, hypertension, physical inactivity, and advancing age) are major risk factors for developing CVD and are increasing in prevalence. Individuals in low-income and middle-income countries are undergoing a major shift in cardiovascular risk factors as they adopt Western lifestyles, a phenomenon that is hastened by industrialization, urbanization, and globalization. In this Perspectives article, I predict the 10 most-promising advances in cardiovascular therapies and interventions. Our improved understanding of CVD might help us, during the next decade, to achieve a transition from treating complex disease to promoting global cardiovascular health.

Efficacy and safety of out-of-hospital intravenous metoprolol administration in anterior ST-segment elevation acute myocardial infarction: insights from the METOCARD-CNIC trial

STUDY OBJECTIVE

We seek to examine the efficacy and safety of prereperfusion emergency medical services (EMS)-administered intravenous metoprolol in anterior ST-segment elevation myocardial infarction patients undergoing eventual primary angioplasty.

METHODS

This is a prespecified subgroup analysis of the Effect of Metoprolol in Cardioprotection During an Acute Myocardial Infarction trial population, who all eventually received oral metoprolol within 12 to 24 hours. We studied patients receiving intravenous metoprolol by EMS and compared them with others treated by EMS but not receiving intravenous metoprolol. Outcomes included infarct size and left ventricular ejection fraction on cardiac magnetic resonance imaging at 1 week, and safety by measuring the incidence of the predefined combined endpoint (composite of death, malignant ventricular arrhythmias, advanced atrioventricular block, cardiogenic shock, or reinfarction) within the first 24 hours.

RESULTS

From the total population of the trial (N=270), 147 patients (54%) were recruited during out-of-hospital assistance and transferred to the primary angioplasty center (74 intravenous metoprolol and 73 controls). Infarct size was smaller in patients receiving intravenous metoprolol compared with controls (23.4 [SD 15.0] versus 34.0 [SD 23.7] g; adjusted difference -11.4; 95% confidence interval [CI] -18.6 to -4.3). Left ventricular ejection fraction was higher in the intravenous metoprolol group (48.1% [SD 8.4%] versus 43.1% [SD 10.2%]; adjusted difference 5.0; 95% CI 1.6 to 8.4). Metoprolol administration did not increase the incidence of the prespecified safety combined endpoint: 6.8% versus 17.8% in controls (risk difference -11.1; 95% CI -21.5 to -0.6).

CONCLUSION

Out-of-hospital administration of intravenous metoprolol by EMS within 4.5 hours of symptom onset in our subjects reduced infarct size and improved left ventricular ejection fraction with no excess of adverse events during the first 24 hours.

β3 adrenergic receptor selective stimulation during ischemia/reperfusion improves cardiac function in translational models through inhibition of mPTP opening in cardiomyocytes

Selective stimulation of β3 adrenergic-receptor (β3AR) has been shown to reduce infarct size in a mouse model of myocardial ischemia/reperfusion. However, its functional long-term effect and the cardioprotective mechanisms at the level of cardiomyocytes have not been elucidated, and the impact of β3AR stimulation has not been evaluated in a more translational large animal model. This study aimed at evaluating pre-perfusion administration of BRL37344 both in small and large animal models of myocardial ischemia/reperfusion. Pre-reperfusion administration of the β3AR agonist BRL37344 (5 μg/kg) reduced infarct size at 2-and 24-h reperfusion in wild-type mice. Long-term (12-weeks) left ventricular (LV) function assessed by echocardiography and cardiac magnetic resonance (CMR) was significantly improved in β3AR agonist-treated mice. Incubation with β3AR agonist (BRL37344, 7 μmol/L) significantly reduced cell death in isolated adult mouse cardiomyocytes during hypoxia/reoxygenation and decreased susceptibility to deleterious opening of the mitochondrial permeability transition pore (mPTP), via a mechanism dependent on the Akt-NO signaling pathway. Pre-reperfusion BRL37344 administration had no effect on infarct size in cyclophilin-D KO mice, further implicating mPTP in the mechanism of protection. Large-white pigs underwent percutaneous coronary ischemia/reperfusion and 3-T CMR at 7 and 45 days post-infarction. Pre-perfusion administration of BRL37344 (5 μg/kg) decreased infarct size and improved long-term LV contractile function. A single-dose administration of β3AR agonist before reperfusion decreased infarct size and resulted in a consistent and long-term improvement in cardiac function, both in small and large animal models of myocardial ischemia/reperfusion. This protection appears to be executed through inhibition of mPTP opening in cardiomyocytes.

Cardioprotection and pharmacological therapies in acute myocardial infarction: Challenges in the current era

In patients with an acute ST-segment elevation myocardial infarction, timely myocardial reperfusion using primary percutaneous coronary intervention is the most effective therapy for limiting myocardial infarct size, preserving left-ventricular systolic function and reducing the onset of heart failure. Within minutes after the restoration of blood flow, however, reperfusion itself results in additional damage, also known as myocardial ischemia-reperfusion injury. An improved understanding of the pathophysiological mechanisms underlying reperfusion injury has resulted in the identification of several promising pharmacological (cyclosporin-A, exenatide, glucose-insulin-potassium, atrial natriuretic peptide, adenosine, abciximab, erythropoietin, metoprolol and melatonin) therapeutic strategies for reducing the severity of myocardial reperfusion injury. Many of these agents have shown promise in initial proof-of-principle clinical studies. In this article, we review the pathophysiology underlying myocardial reperfusion injury and highlight the potential pharmacological interventions which could be used in the future to prevent reperfusion injury and improve clinical outcomes in patients with coronary heart disease.

Effect of early metoprolol on infarct size in ST-segment-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention: the Effect of Metoprolol in Cardioprotection During an Acute Myocardial Infarction (METOCARD-CNIC) trial

BACKGROUND

The effect of β-blockers on infarct size when used in conjunction with primary percutaneous coronary intervention is unknown. We hypothesize that metoprolol reduces infarct size when administered early (intravenously before reperfusion).

METHODS AND RESULTS

Patients with Killip class II or less anterior ST-segment-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention within 6 hours of symptoms onset were randomized to receive intravenous metoprolol (n=131) or not (control, n=139) before reperfusion. All patients without contraindications received oral metoprolol within 24 hours. The predefined primary end point was infarct size on magnetic resonance imaging performed 5 to 7 days after STEMI. Magnetic resonance imaging was performed in 220 patients (81%). Mean ± SD infarct size by magnetic resonance imaging was smaller after intravenous metoprolol compared with control (25.6 ± 15.3 versus 32.0 ± 22.2 g; adjusted difference, -6.52; 95% confidence interval, -11.39 to -1.78; P=0.012). In patients with pre-percutaneous coronary intervention Thrombolysis in Myocardial Infarction grade 0 to 1 flow, the adjusted treatment difference in infarct size was -8.13 (95% confidence interval, -13.10 to -3.16; P=0.0024). Infarct size estimated by peak and area under the curve creatine kinase release was measured in all study populations and was significantly reduced by intravenous metoprolol. Left ventricular ejection fraction was higher in the intravenous metoprolol group (adjusted difference, 2.67%; 95% confidence interval, 0.09-5.21; P=0.045). The composite of death, malignant ventricular arrhythmia, cardiogenic shock, atrioventricular block, and reinfarction at 24 hours in the intravenous metoprolol and control groups was 7.1% and 12.3%, respectively (P=0.21).

CONCLUSIONS

In patients with anterior Killip class II or less ST-segment-elevation myocardial infarction undergoing primary percutaneous coronary intervention, early intravenous metoprolol before reperfusion reduced infarct size and increased left ventricular ejection fraction with no excess of adverse events during the first 24 hours after STEMI.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01311700. EUDRACT number: 2010-019939-35.

The effect of c-fos on acute myocardial infarction and the significance of metoprolol intervention in a rat model

Over-expression of c-fos may play a role in some diseases. Research pertaining to the expression of c-fos in acute myocardial ınfarction (AMI) is rare, and the detailed role of c-fos in AMI has not been reported. Therefore, the purpose of this project was to elucidate the detailed effect of c-fos on AMI rats and evaluate the effect of a metoprolol intervention. An AMI rat model was established for the purposes of this study. The expression of c-fos in AMI was evaluated via immunohistochemical analysis and in situ hybridization. Simultaneously, we investigated the effect of c-fos on AMI rats via medicinal treatment with c-fos monoclonal antibody, isoproterenol, and metoprolol. Positive c-Fos protein expression and c-fos mRNA expression in cardiomyocytes were increased at 1, 3, 7, and 10 days after ligation in AMI rats compared with a sham-operated group. Peak expression occurred at 3 days after ligation. The weight percentage fraction of infarct size was decreased in rats treated with c-fos monoclonal antibody compared with the control normal saline treatment group. The weight percentage fraction of infarction size was increased after c-fos was increased via the administration of isoproterenol. c-Fos protein expression and the infarct size in rats treated with metoprolol were also decreased compared with the control normal saline treatment group. The results showed that c-fos expression rapidly increased after coronary ligation; c-fos plays an important role in myocardial lesions and is likely to be involved in the pathogenesis of AMI as well. Metoprolol can inhibit the expression of c-fos and has a positive therapeutic effect on rats after AMI; the involvement effect of metoprolol on myocardial infarction might be correlated with its effect on the inhibition of c-fos.

Imagining the future of diagnostic imaging

Cardiovascular imaging has become essential to achieving a better understanding of cardiovascular diseases. Due to the advent of new technology and the refinement of existing technologies, imaging's role has extended into the biological, functional, and hemodynamic diagnosis of multiple pathophysiologic processes. Current and future trends in cardiovascular imaging will focus on improving early diagnosis of vascular disease, so as to be able to promote cardiovascular health, and on its development as a useful tool in clinical decision-making. Imaging is also increasingly used to quantify the effect of novel therapies. The rapid development of molecular imaging and fusion imaging techniques improves our understanding of cardiovascular processes from the molecular and cellular points of view and makes it possible to design and test new preventive interventions. The proliferation and integration of imaging techniques in different clinical areas and their role in "translational imaging" plays an important part in the implementation of personalized therapeutic and preventive management strategies for patients with cardiovascular disease.

Early intravenous beta-blockers in patients with acute coronary syndrome--a meta-analysis of randomized trials

BACKGROUND

Intravenous (IV) beta-blockade is currently a Class IIa recommendation in early management of patients with acute coronary syndromes (ACS) without obvious contraindications.

METHODS

We searched the PubMed, EMBASE and the Cochrane Register for Controlled Clinical Trials for randomized clinical trials from 1965 through December, 2011, comparing intravenous beta-blockers administered within 12 hours of presentation of ACS with standard medical therapy and/or placebo. The primary outcome assessed was the risk of short-term (in-hospital mortality-with maximum follow up duration of 90 days) all-cause mortality in the intervention group versus the comparator group. The secondary outcomes assessed were ventricular tachyarrhythmias, myocardial reinfarction, cardiogenic shock, and stroke. Pooled treatment effects were estimated using relative risk with Mantel-Haenszel risk ratio, using a random-effects model.

RESULTS

Sixteen studies enrolling 73,396 participants met the inclusion ⁄ exclusion criteria. In- hospital mortality was reduced 8% with intravenous beta-blockers, RR=0.92 (95% CI, 0.86-1.00; p=0.04) when compared with controls. Moreover, intravenous beta-blockade reduced the risk of ventricular tachyarrhythmias (RR=0.61; 95 % CI 0.47-0.79; p=0.0003) and myocardial reinfarction (RR=0.73, 95 % CI 0.59-0.91; p=0.004) without increase in the risk of cardiogenic shock, (RR=1.02; 95% CI 0.77-1.35; p=0.91) or stroke (RR=0.58; 95 % CI 0.17-1.98; p=0.38).

CONCLUSIONS

Intravenous beta-blockers early in the course of appropriate patients with ACS appears to be associated with significant reduction in the risk of short-term cardiovascular outcomes, including a reduction in the risk of all-cause mortality.

Study design for the "effect of METOprolol in CARDioproteCtioN during an acute myocardial InfarCtion" (METOCARD-CNIC): a randomized, controlled parallel-group, observer-blinded clinical trial of early pre-reperfusion metoprolol administration in ST-segment elevation myocardial infarction

BACKGROUND

Infarct size predicts post-infarction mortality. Oral β-blockade within 24 hours of a ST-segment elevation acute myocardial infarction (STEMI) is a class-IA indication, however early intravenous (IV) β-blockers initiation is not encouraged. In recent magnetic resonance imaging (MRI)-based experimental studies, the β(1)-blocker metoprolol has been shown to reduce infarct size only when administered before coronary reperfusion. To date, there is not a single trial comparing the pre- vs. post-reperfusion β-blocker initiation in STEMI.

OBJECTIVE

The METOCARD-CNIC trial is testing whether the early initiation of IV metoprolol before primary percutaneous coronary intervention (pPCI) could reduce infarct size and improve outcomes when compared to oral post-pPCI metoprolol initiation.

DESIGN

The METOCARD-CNIC trial is a randomized parallel-group single-blind (to outcome evaluators) clinical effectiveness trial conducted in 5 Counties across Spain that will enroll 220 participants. Eligible are 18- to 80-year-old patients with anterior STEMI revascularized by pPCI ≤6 hours from symptom onset. Exclusion criteria are Killip-class ≥III, atrioventricular block or active treatment with β-blockers/bronchodilators. Primary end point is infarct size evaluated by MRI 5 to 7 days post-STEMI. Prespecified major secondary end points are salvage-index, left ventricular ejection fraction recovery (day 5-7 to 6 months), the composite of (death/malignant ventricular arrhythmias/reinfarction/admission due to heart failure), and myocardial perfusion.

CONCLUSIONS

The METOCARD-CNIC trial is testing the hypothesis that the early initiation of IV metoprolol pre-reperfusion reduces infarct size in comparison to initiation of oral metoprolol post-reperfusion. Given the implications of infarct size reduction in STEMI, if positive, this trial might evidence that a refined use of an approved inexpensive drug can improve outcomes of patients with STEMI.

The future: therapy of myocardial protection

The main determinant of myocardial necrosis following an acute myocardial infarction (AMI) is duration of ischemia. Infarct size is a strong independent predictor of postinfarction mortality. Interventions able to protect the myocardium from death during an AMI (cardioprotection) are urgently needed. Myocardial injury associated with reperfusion (ischemia/reperfusion injury [I/R]) significantly contributes to the final necrotic size. Duration of ischemia can only be reduced by social and emergency medical services--hospital collaborative programs. However, for a given duration of ischemia, infarct size can be limited by reducing reperfusion injury. Despite the fact that several therapies have been shown to reduce I/R injury in animal models, translation to humans has been frustrating. The cost of developing new drugs able to reduce I/R injury is huge, and this is a major roadblock in the field of cardioprotection. Recent studies have proposed that old, inexpensive drugs--in human use for decades (e.g., β-blockers and cyclosporine, among others)--can reduce I/R injury when administered intravenously before coronary opening. The demonstration of such a cardioprotective effect should have a significant impact in the care of AMI patients.

[Modulation of the beta-adrenergic system during acute myocardial infarction: rationale for a new clinical trial]

Acute myocardial infarction is caused by sudden coronary artery occlusion. Persistent ischemia results in necrosis of the myocardial tissue supplied by the occluded vessel. It has recently been shown that the final size of the infarct is a major predictor of future clinical events, and is, therefore, used as a surrogate outcome in clinical trials. Moreover, it has become clear that the duration of ischemia in the main determinant of the success of myocardial salvage (i.e. of non-necrotic at-risk myocardium). In addition to minimizing the time between symptom onset and reperfusion, there is considerable interest in finding therapies that can further limit the size of the infarction (i.e. cardioprotective therapies) and they are the focus of numerous clinical studies. Oral β-blockade within the first few hours of an AMI is a class-IA indication in clinical practice guidelines. However, early intravenous β-blockade, even before coronary artery reperfusion, is not routinely recommended. Preclinical research has demonstrated that the selectiveβ1-blocker metoprolol is able to reduce the infarct size only when administered before coronary artery reperfusion, which indicates that its cardioprotective properties are secondary to its ability to reduce reperfusion injury. In addition, retrospective studies of AMI suggest that starting intravenous β-blockade early has clinical benefits (i.e. lower mortality and better recovery of left ventricular contractility) in patients without contraindications. Our general hypothesis is that early administration of metoprolol (i.e. intravenously before reperfusion) results in smaller infarcts than administering the drug orally after reperfusion. The Effect of METOprolol in CARDioproteCtioN during an acute myocardial InfarCtion (METOCARD-CNIC) trial will test this hypothesis in patients with ST-segment elevation AMI.

Lethal myocardial reperfusion injury: a necessary evil?

Despite being the most effective means of limiting infarct size, coronary reperfusion comes at a price and induces additional damage to the myocardium. Lethal reperfusion injury (death of myocytes that were viable at the time of reperfusion) is an increasingly acknowledged phenomenon. There are many interconnected mechanisms involved in this type of cell death. Calcium overload (generating myocyte hypercontracture), rapid recovery of physiological pH, neutrophil infiltration of the ischemic area, opening of the mitochondrial permeability-transition-pore (PTP), and apoptotic cell death are among the more important mechanisms involved in reperfusion injury. The activation of a group of proteins called reperfusion injury salvage kinases (RISK) pathway confers protection against reperfusion injury, mainly by inhibiting the opening of the mitochondrial PTP. Many interventions have been tested in human trials triggered by encouraging animal studies. In the present review we will explain in detail the main mechanism involved in reperfusion injury, as well as the various approaches (pre-clinical and human trials) performed targeting these mechanisms. Currently, no intervention has been consistently shown to reduce reperfusion injury in large randomized multicenter trials, but the research in this field is intense and the future is highly promising.