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

Effect of early metoprolol before PCI in ST-segment elevation myocardial infarction on infarct size and left ventricular ejection fraction. A systematic review and meta-analysis of clinical trials

Aim

This meta‐analysis aims to look at the impact of early intravenous Metoprolol in ST‐segment elevation myocardial infarction (STEMI) before percutaneous coronary intervention (PCI) on infarct size, as measured by cardio magnetic resonance (CMR) and left ventricular ejection fraction.

Methods

We searched the following databases: PubMed, Scopus, Cochrane library, and Web of Science. We included only randomized control trials that reported the use of early intravenous Metoprolol in STEMI before PCI on infarct size, as measured by CMR and left ventricular ejection fraction. RevMan software 5.4 was used for performing the analysis.

Results

Following a literature search, 340 publications were found. Finally, 18 studies were included for the systematic review, and 8 clinical trials were included in the meta‐analysis after the full‐text screening. At 6 months, the pooled effect revealed a statistically significant association between Metoprolol and increased left ventricular ejection fraction (LVEF) (%) compared to controls (mean difference [MD] = 3.57, [95% confidence interval [CI] = 2.22–4.92], p < .00001), as well as decreased infarcted myocardium(g) compared to controls (MD = −3.84, [95% [CI] = −5.75 to −1.93], p < .0001). At 1 week, the pooled effect revealed a statistically significant association between Metoprolol and increased LVEF (%) compared to controls (MD = 2.98, [95% CI = 1.26−4.69], p = .0007), as well as decreased infarcted myocardium(%) compared to controls (MD = −3.21, [95% CI = −5.24 to −1.18], p = .002).

Conclusion

A significant decrease in myocardial infarction and increase in LVEF (%) was linked to receiving Metoprolol at 1 week and 6‐month follow‐up.

Intravenous metoprolol during ongoing STEMI ameliorates markers of ischemic injury: a METOCARD-CNIC trial electrocardiographic study

Besides its protective effect against neutrophil-mediated injury at reperfusion, intravenous (IV) metoprolol was recently shown to reduce the progression of ischemic injury in a pig model of ST-segment elevation myocardial infarction (STEMI). Here, we tested the hypothesis that IV metoprolol administration in humans with ongoing STEMI blunts the time‑dependent progression of ischemic injury assessed by serial electrocardiogram (ECG) evaluations before reperfusion. The METOCARD-CNIC trial randomized 270 anterior STEMI patients to IV metoprolol or control before reperfusion by percutaneous coronary intervention (PCI). In 139 patients (69 IV metoprolol, 70 controls), two ECGs were available (ECG-1 before randomization, ECG-2 pre-PCI). Between-group ECG differences were analyzed using univariate and multivariate regression models. No significant between-group differences were observed on ECG-1. On ECG-2, patients who received IV metoprolol had a narrower QRS than those in the control group (84 ms vs. 90 ms, p = 0.029), a lower prevalence of QRS distortion (10% vs. 26%, p = 0.017), and a lower sum of anterior and total ST-segment elevation (10.1 mm vs. 13.6 mm, p = 0.014 and 10.4 mm vs. 14.0 mm, p = 0.015, respectively). Adjusted analysis revealed similar results. Significant associations were observed between ECG-2 variables and cardiac magnetic resonance imaging measurements (extent of myocardial edema, infarct size, microvascular obstruction, and left-ventricular ejection fraction) after STEMI. In summary, IV metoprolol administration before reperfusion ameliorates ECG markers of myocardial ischemia in anterior STEMI patients. These data confirm that IV metoprolol is able to reduce ischemic injury and highlight the ability of ECG analysis to provide relevant real-time information on the effect of cardioprotective therapies before reperfusion.

Five-Year Outcomes and Prognostic Value of Feature-Tracking Cardiovascular Magnetic Resonance in Patients Receiving Early Prereperfusion Metoprolol in Acute Myocardial Infarction

The aim of the present study was to investigate the long-term impact of early intravenous metoprolol in ST-segment elevation myocardial infarction (STEMI) patients in terms of left ventricular (LV) strain with feature-tracking cardiovascular magnetic resonance (CMR) and its association with prognosis. A total of 270 patients with first anterior STEMI enrolled in the randomized METOCARD-CNIC clinical trial, assigned to receive up to 15 mg intravenous metoprolol before primary percutaneous coronary intervention versus conventional STEMI therapy, were included. LV global circumferential (GCS) and longitudinal (GLS) strain were assessed with feature-tracking CMR at 1 week after STEMI in 215 patients. The occurrence of major adverse cardiac events (MACE) at 5-year follow-up was the primary end point. Among 270 patients enrolled, 17 of 139 patients assigned to metoprolol arm and 31 of 131 patients assigned to control arm experienced MACE (hazard ratio [HR] 0.500, 95% confidence interval [CI] 0.277 to 0.903; p = 0.022). Impaired LV GCS and GLS strain were significantly associated with increased occurrence of MACE (GCS: HR 1.208, 95% CI 1.076 to 1.356, p =0.001; GLS: HR 1.362, 95% CI 1.180 to 1.573, p < 0.001). On multivariable analysis, LV GLS provided incremental prognostic value over late gadolinium enhancement (LGE) and LV ejection fraction (LVEF) (LGE + LVEF chi-square = 12.865, LGE + LVEF + GLS chi-square = 18.459; p =0.012). Patients with GLS ≥-11.5% (above median value) who received early intravenous metoprolol were 64% less likely to experience MACE than their counterparts with same degree of GLS impairment (HR 0.356, 95% CI 0.129 to 0.979; p = 0.045). In conclusion, early intravenous metoprolol has a long-term beneficial prognostic effect, particularly in patients with severely impaired LV systolic function. LV GLS with feature-tracking CMR early after percutaneous coronary intervention offers incremental prognostic value over conventional CMR parameters in risk stratification of STEMI patients.

Coexistence of transmural and lateral wavefront progression of myocardial infarction in the human heart

INTRODUCTION AND OBJECTIVES

According to the wavefront phenomenon described in the late 1970s, myocardial infarction triggered by acute coronary occlusion progresses with increasing duration of ischemia as a transmural wavefront from the subendocardium toward the subepicardium. However, whether wavefront progression of necrosis also occurs laterally has been disputed. We aimed to assess the transmural and lateral spread of myocardial damage after acute myocardial infarction in humans and to evaluate the impact of metoprolol on these.

METHODS

We assessed myocardial infarction in the transmural and lateral dimensions in a cohort of 220 acute ST-segment elevation myocardial infarction (STEMI) patients from the METOCARD-CNIC trial (Effect of Metoprolol in Cardioprotection During an Acute Myocardial Infarction). The patients underwent cardiac magnetic resonance imaging at 5 to 7 days and 6 months post-STEMI.

RESULTS

On day 5 to 7 post-STEMI cardiac magnetic resonance, there was a strong linear correlation between the transmural and lateral extent of infarction (delayed gadolinium enhancement) (r=-0.88; P<.001). Six months after STEMI, myocardial scarring (delayed gadolinium enhancement) was significantly less extensive in the transmural and lateral dimensions, suggesting that infarct resorption occurs in both. Furthermore, progression in both directions occurred both in patients receiving metoprolol and control patients, implying that myocardial salvage occurs both in the transmural and the lateral direction.

CONCLUSIONS

Our findings challenge the assumption that irreversible injury does not spread laterally. A "circumferential" or multidirectional wavefront would imply that cardioprotective therapies might produce meaningful salvage at lateral borders of the infarct. This trial was registered at ClinicalTrial.gov (Identifier: NCT01311700).

Left ventricular functional recovery of infarcted and remote myocardium after ST-segment elevation myocardial infarction (METOCARD-CNIC randomized clinical trial substudy)

BACKGROUND

We aimed to evaluate the effect of early intravenous metoprolol treatment, microvascular obstruction (MVO), intramyocardial hemorrhage (IMH) and adverse left ventricular (LV) remodeling on the evolution of infarct and remote zone circumferential strain after acute anterior ST-segment elevation myocardial infarction (STEMI) with feature-tracking cardiovascular magnetic resonance (CMR).

METHODS

A total of 191 patients with acute anterior STEMI enrolled in the METOCARD-CNIC randomized clinical trial were evaluated. LV infarct zone and remote zone circumferential strain were measured with feature-tracking CMR at 1 week and 6 months after STEMI.

RESULTS

In the overall population, the infarct zone circumferential strain significantly improved from 1 week to 6 months after STEMI (- 8.6 ± 9.0% to - 14.5 ± 8.0%; P < 0.001), while no changes in the remote zone strain were observed (- 19.5 ± 5.9% to - 19.2 ± 3.9%; P = 0.466). Patients who received early intravenous metoprolol had significantly more preserved infarct zone circumferential strain compared to the controls at 1 week (P = 0.038) and at 6 months (P = 0.033) after STEMI, while no differences in remote zone strain were observed. The infarct zone circumferential strain was significantly impaired in patients with MVO and IMH compared to those without (P < 0.001 at 1 week and 6 months), however it improved between both time points regardless of the presence of MVO or IMH (P < 0.001). In patients who developed adverse LV remodeling (defined as ≥ 20% increase in LV end-diastolic volume) remote zone circumferential strain worsened between 1 week and 6 months after STEMI (P = 0.036), while in the absence of adverse LV remodeling no significant changes in remote zone strain were observed.

CONCLUSIONS

Regional LV circumferential strain with feature-tracking CMR allowed comprehensive evaluation of the sequelae of an acute STEMI treated with primary percutaneous coronary intervention and demonstrated long-lasting cardioprotective effects of early intravenous metoprolol.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01311700. Registered 8 March 2011 - Retrospectively registered.

ArrhythmoGenoPharmacoTherapy

This review is focusing on the understanding of various factors and components governing and controlling the occurrence of ventricular arrhythmias including (i) the role of various ion channel-related changes in the action potential (AP), (ii) electrocardiograms (ECGs), (iii) some important arrhythmogenic mediators of reperfusion, and pharmacological approaches to their attenuation. The transmembrane potential in myocardial cells is depending on the cellular concentrations of several ions including sodium, calcium, and potassium on both sides of the cell membrane and active or inactive stages of ion channels. The movements of Na+, K+, and Ca2+ via cell membranes produce various currents that provoke AP, determining the cardiac cycle and heart function. A specific channel has its own type of gate, and it is opening and closing under specific transmembrane voltage, ionic, or metabolic conditions. APs of sinoatrial (SA) node, atrioventricular (AV) node, and Purkinje cells determine the pacemaker activity (depolarization phase 4) of the heart, leading to the surface manifestation, registration, and evaluation of ECG waves in both animal models and humans. AP and ECG changes are key factors in arrhythmogenesis, and the analysis of these changes serve for the clarification of the mechanisms of antiarrhythmic drugs. The classification of antiarrhythmic drugs may be based on their electrophysiological properties emphasizing the connection between basic electrophysiological activities and antiarrhythmic properties. The review also summarizes some important mechanisms of ventricular arrhythmias in the ischemic/reperfused myocardium and permits an assessment of antiarrhythmic potential of drugs used for pharmacotherapy under experimental and clinical conditions.

Beta-blockers for suspected or diagnosed acute myocardial infarction

BACKGROUND

Cardiovascular disease is the number one cause of death globally. According to the World Health Organization, 7.4 million people died from ischaemic heart diseases in 2012, constituting 15% of all deaths. Acute myocardial infarction is caused by blockage of the blood supplied to the heart muscle. Beta-blockers are often used in patients with acute myocardial infarction. Previous meta-analyses on the topic have shown conflicting results ranging from harms, neutral effects, to benefits. No previous systematic review using Cochrane methodology has assessed the effects of beta-blockers for acute myocardial infarction.

OBJECTIVES

To assess the benefits and harms of beta-blockers compared with placebo or no intervention in people with suspected or diagnosed acute myocardial infarction.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, Science Citation Index Expanded and BIOSIS Citation Index in June 2019. We also searched the WHO International Clinical Trials Registry Platform, ClinicalTrials.gov, Turning Research into Practice, Google Scholar, SciSearch, and the reference lists of included trials and previous reviews in August 2019.

SELECTION CRITERIA

We included all randomised clinical trials assessing the effects of beta-blockers versus placebo or no intervention in people with suspected or diagnosed acute myocardial infarction. Trials were included irrespective of trial design, setting, blinding, publication status, publication year, language, and reporting of our outcomes.

DATA COLLECTION AND ANALYSIS

We followed the Cochrane methodological recommendations. Four review authors independently extracted data. Our primary outcomes were all-cause mortality, serious adverse events according to the International Conference on Harmonization - Good Clinical Practice (ICH-GCP), and major adverse cardiovascular events (composite of cardiovascular mortality and non-fatal myocardial infarction during follow-up). Our secondary outcomes were quality of life, angina, cardiovascular mortality, and myocardial infarction during follow-up. Our primary time point of interest was less than three months after randomisation. We also assessed the outcomes at maximum follow-up beyond three months. Due to risk of multiplicity, we calculated a 97.5% confidence interval (CI) for the primary outcomes and a 98% CI for the secondary outcomes. We assessed the risks of systematic errors through seven bias domains in accordance to the instructions given in the Cochrane Handbook. The quality of the body of evidence was assessed by GRADE.

MAIN RESULTS

We included 63 trials randomising a total of 85,550 participants (mean age 57.4 years). Only one trial was at low risk of bias. The remaining trials were at high risk of bias. The quality of the evidence according to GRADE ranged from very low to high. Fifty-six trials commenced beta-blockers during the acute phase of acute myocardial infarction and seven trials during the subacute phase. At our primary time point 'less than three months follow-up', meta-analysis showed that beta-blockers versus placebo or no intervention probably reduce the risk of a reinfarction during follow-up (risk ratio (RR) 0.82, 98% confidence interval (CI) 0.73 to 0.91; 67,562 participants; 18 trials; moderate-quality evidence) with an absolute risk reduction of 0.5% and a number needed to treat for an additional beneficial outcome (NNTB) of 196 participants. However, we found little or no effect of beta-blockers when assessing all-cause mortality (RR 0.94, 97.5% CI 0.90 to 1.00; 80,452 participants; 46 trials/47 comparisons; high-quality evidence) with an absolute risk reduction of 0.4% and cardiovascular mortality (RR 0.99, 95% CI 0.91 to 1.08; 45,852 participants; 1 trial; moderate-quality evidence) with an absolute risk reduction of 0.4%. Regarding angina, it is uncertain whether beta-blockers have a beneficial or harmful effect (RR 0.70, 98% CI 0.25 to 1.84; 98 participants; 3 trials; very low-quality evidence) with an absolute risk reduction of 7.1%. None of the trials specifically assessed nor reported serious adverse events according to ICH-GCP. Only two trials specifically assessed major adverse cardiovascular events, however, no major adverse cardiovascular events occurred in either trial. At maximum follow-up beyond three months, meta-analyses showed that beta-blockers versus placebo or no intervention probably reduce the risk of all-cause mortality (RR 0.93, 97.5% CI 0.86 to 0.99; 25,210 participants; 21 trials/22 comparisons; moderate-quality evidence) with an absolute risk reduction of 1.1% and a NNTB of 91 participants, and cardiovascular mortality (RR 0.90, 98% CI 0.83 to 0.98; 22,457 participants; 14 trials/15 comparisons; moderate-quality evidence) with an absolute risk reduction of 1.2% and a NNTB of 83 participants. However, it is uncertain whether beta-blockers have a beneficial or harmful effect when assessing major adverse cardiovascular events (RR 0.81, 97.5% CI 0.40 to 1.66; 475 participants; 4 trials; very low-quality evidence) with an absolute risk reduction of 1.7%; reinfarction (RR 0.89, 98% CI 0.75 to 1.08; 6825 participants; 14 trials; low-quality evidence) with an absolute risk reduction of 0.9%; and angina (RR 0.64, 98% CI 0.18 to 2.0; 844 participants; 2 trials; very low-quality evidence). None of the trials specifically assessed nor reported serious adverse events according to ICH-GCP. None of the trials assessed quality of life. We identified two ongoing randomised clinical trials investigating the effect of early administration of beta-blockers after percutaneous coronary intervention or thrombolysis to patients with an acute myocardial infarction and one ongoing trial investigating the effect of long-term beta-blocker therapy.

AUTHORS' CONCLUSIONS

Our present review indicates that beta-blockers for suspected or diagnosed acute myocardial infarction probably reduce the short-term risk of a reinfarction and the long-term risk of all-cause mortality and cardiovascular mortality. Nevertheless, it is most likely that beta-blockers have little or no effect on the short-term risk of all-cause mortality and cardiovascular mortality. Regarding all remaining outcomes (serious adverse events according to ICH-GCP, major adverse cardiovascular events (composite of cardiovascular mortality and non-fatal myocardial infarction during follow-up), the long-term risk of a reinfarction during follow-up, quality of life, and angina), further information is needed to confirm or reject the clinical effects of beta-blockers on these outcomes for people with or suspected of acute myocardial infarction.

Ischemia Reperfusion Injury: Mechanisms of Damage/Protection and Novel Strategies for Cardiac Recovery/Regeneration

Ischemic diseases in an aging population pose a heavy social encumbrance. Moreover, current therapeutic approaches, which aimed to prevent or minimize ischemia-induced damage, are associated with relevant costs for healthcare systems. Early reperfusion by primary percutaneous coronary intervention (PPCI) has undoubtedly improved patient's outcomes; however, the prevention of long-term complications is still an unmet need. To face these hurdles and improve patient's outcomes, novel pharmacological and interventional approaches, alone or in combination, reducing myocardium oxygen consumption or supplying blood flow via collateral vessels have been proposed. A number of clinical trials are ongoing to validate their efficacy on patient's outcomes. Alternative options, including stem cell-based therapies, have been evaluated to improve cardiac regeneration and prevent scar formation. However, due to the lack of long-term engraftment, more recently, great attention has been devoted to their paracrine mediators, including exosomes (Exo) and microvesicles (MV). Indeed, Exo and MV are both currently considered to be one of the most promising therapeutic strategies in regenerative medicine. As a matter of fact, MV and Exo that are released from stem cells of different origin have been evaluated for their healing properties in ischemia reperfusion (I/R) settings. Therefore, this review will first summarize mechanisms of cardiac damage and protection after I/R damage to track the paths through which more appropriate interventional and/or molecular-based targeted therapies should be addressed. Moreover, it will provide insights on novel non-invasive/invasive interventional strategies and on Exo-based therapies as a challenge for improving patient's long-term complications. Finally, approaches for improving Exo healing properties, and topics still unsolved to move towards Exo clinical application will be discussed.

Role of Beta-blockers in Cardiovascular Disease in 2019

Beta-blockers are the cornerstone of treatment for various cardiovascular conditions. Although their effects have classically been considered to be driven by their antagonistic and competitive action on beta-adrenergic receptors, nowadays it is known that their effect goes beyond that of mere competition with catecholamines on these receptors. Beta-blockers were discovered as antianginal drugs in the 1960s and are currently widely used in heart failure, arrhythmias, and ischemic heart disease. In this article, we review the evidence for the beneficial effects of beta-blockers in these conditions, as well as the current recommendations in clinical practice guidelines for their use. Surprisingly, despite having been prescribed for more than 4 decades, new, previously unnoticed mechanisms of action on cellular compartments are still being discovered, which continues to open up new horizons for their use. All in all, beta-blockers are one of the most fascinating drug groups in our therapeutic armamentarium.

Low altitude simulation without hypoxia improves left ventricular function after myocardial infarction by reducing ventricular afterload

Humans have a lower risk of death from myocardial infarction (MI) living at low elevations (<2500 m), which are not high enough to induce hypoxia. Both chronic hypoxia pre-MI, achieved by altitude simulation >5000 m, and intermittent hypobaric hypoxia post-MI can reduce MI size in rodents, and it is believed that hypoxia is the key stimulus. To explore mechanisms beyond hypoxia we studied whether altitude simulation <2500 m would also be associated with reduced infarct size. We performed left-anterior descending artery ligation on C57BL6 mice. Control mice (n = 12) recovered at 754 mmHg (atmospheric pressure, control), and treatment group mice (n = 13) were placed in a hypobaric chamber to recover 3-hours daily at 714 mmHg for 1 week. Echocardiographic evaluation of left ventricular function was performed on Day 0, Day 1 and Day 8. Intermittent hypobaric treatment was associated with a 14.2±5.3% improvement in ejection fraction for treatment group mice (p<0.01 vs. Day 1), with no change observed in control mice. Cardiac output, stroke volume, and infarct size were also improved in treated mice, but no changes were observed in HIF-1 activation or neovascularization. Next, we studied the acute hemodynamic effects of low altitude stimulation in intact mice breathing 100% oxygen using left ventricular catheterization and recording of pressure-volume loops. Acute reductions in barometric pressure from 754 mmHg to 714 mmHg and 674 mmHg were associated with reduced systemic vascular resistance, increased stroke volume and cardiac output, and no change in blood pressure or heart rate. Ex-vivo vascular function was studied using murine mesenteric artery segments. Acute reductions in barometric pressure were associated with greater vascular distensibility. We conclude that intermittent hypobaric treatment using simulated altitudes <2500 m reduces infarct size and increases ventricular function post-MI, and that these changes are related to altered arterial function and not hypoxia-associated neovascularization.

Effect of Early Metoprolol During ST-Segment Elevation Myocardial Infarction on Left Ventricular Strain: Feature-Tracking Cardiovascular Magnetic Resonance Substudy From the METOCARD-CNIC Trial

OBJECTIVES

This study sought to evaluate the effect of early intravenous metoprolol on left ventricular (LV) strain assessed with feature-tracking cardiovascular magnetic resonance (CMR).

BACKGROUND

Early intravenous metoprolol before primary percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI) portends better outcomes in the METOCARD-CNIC (Effect of Metoprolol in Cardioprotection During an Acute Myocardial Infarction) trial.

METHODS

A total of 197 patients with acute anterior STEMI who were enrolled in the METOCARD-CNIC trial (100 allocated to intravenous metoprolol before primary PCI and 97 control patients) were evaluated. LV global circumferential strain (GCS) and global longitudinal strain (GLS) were measured with feature-tracking CMR at 1 week and 6 months after STEMI and compared between randomization groups.

RESULTS

Patients who received early intravenous metoprolol had significantly more preserved LV strain compared with the control patients at 1 week after STEMI (GCS -13.9 ± 3.8% vs. -12.6 ± 3.9%, respectively; p = 0.013; GLS -11.9 ± 2.8% vs. -10.9 ± 3.2%, respectively; p = 0.032). In both groups, LV strain significantly improved during follow-up (mean difference between 6-month and 1-week strain for the metoprolol group: GCS -2.9%, 95% confidence interval [CI]: -3.5% to -2.4%; GLS: -2.9%, 95% CI: -3.4% to -2.4%; both p < 0.001; the control group: GCS -3.4%, 95% CI: -3.9% to -2.8%; GLS -3.4%, 95% CI: -3.9% to -3.0%; both p < 0.001). When dividing the overall cohort of patients in quartiles of GCS and GLS, there were significantly fewer patients in the first quartile (i.e., the worst LV systolic function) who received early intravenous metoprolol compared with control patients at 1 week and 6 months (p < 0.05 for GCS and GLS at both time points).

CONCLUSIONS

In patients with anterior STEMI, early administration of intravenous metoprolol before primary PCI was associated with significantly fewer patients with severely depressed LV GCS and GLS, both at 1 week and 6 months. Feature-tracking CMR represents a complementary tool to evaluate the benefits of cardioprotective therapies. (Effect of METOprolol in CARDioproteCtioN During an Acute Myocardial InfarCtion [METOCARD-CNIC]: NCT01311700).

Predictors of Intramyocardial Hemorrhage After Reperfused ST-Segment Elevation Myocardial Infarction

Background

Findings from recent studies show that microvascular injury consists of microvascular destruction and intramyocardial hemorrhage (IMH). Patients with ST‐segment elevation myocardial infarction (STEMI) with IMH show poorer prognoses than patients without IMH. Knowledge on predictors for the occurrence of IMH after STEMI is lacking. The current study aimed to investigate the prevalence and extent of IMH in patients with STEMI and its relation with periprocedural and clinical variables.

Methods and Results

A multicenter observational cohort study was performed in patients with successfully reperfused STEMI with cardiovascular magnetic resonance examination 5.5±1.8 days after percutaneous coronary intervention. Microvascular injury was visualized using late gadolinium enhancement and T2‐weighted cardiovascular magnetic resonance imaging for microvascular obstruction and IMH, respectively. The median was used as the cutoff value to divide the study population with presence of IMH into mild or extensive IMH. Clinical and periprocedural parameters were studied in relation to occurrence of IMH and extensive IMH, respectively. Of the 410 patients, 54% had IMH. The presence of IMH was independently associated with anterior infarction (odds ratio, 2.96; 95% CI, 1.73–5.06 [P<0.001]) and periprocedural glycoprotein IIb/IIIa inhibitor treatment (odds ratio, 2.67; 95% CI, 1.49–4.80 [P<0.001]). Extensive IMH was independently associated with anterior infarction (odds ratio, 3.76; 95% CI, 1.91–7.43 [P<0.001]). Presence and extent of IMH was associated with larger infarct size, greater extent of microvascular obstruction, larger left ventricular dimensions, and lower left ventricular ejection fraction (all P<0.001).

Conclusions

Occurrence of IMH was associated with anterior infarction and glycoprotein IIb/IIIa inhibitor treatment. Extensive IMH was associated with anterior infarction. IMH was associated with more severe infarction and worse short‐term left ventricular function in patients with STEMI.

Intracoronary Administration of Allogeneic Adipose Tissue-Derived Mesenchymal Stem Cells Improves Myocardial Perfusion But Not Left Ventricle Function, in a Translational Model of Acute Myocardial Infarction

BACKGROUND

Autologous adipose tissue-derived mesenchymal stem cells (ATMSCs) therapy is a promising strategy to improve post-myocardial infarction outcomes. In a porcine model of acute myocardial infarction, we studied the long-term effects and the mechanisms involved in allogeneic ATMSCs administration on myocardial performance.

METHODS AND RESULTS

Thirty-eight pigs underwent 50 minutes of coronary occlusion; the study was completed in 33 pigs. After reperfusion, allogeneic ATMSCs or culture medium (vehicle) were intracoronarily administered. Follow-ups were performed at short (2 days after acute myocardial infarction vehicle-treated, n=10; ATMSCs-treated, n=9) or long term (60 days after acute myocardial infarction vehicle-treated, n=7; ATMSCs-treated, n=7). At short term, infarcted myocardium analysis showed reduced apoptosis in the ATMSCs-treated animals (48.6±6% versus 55.9±5.7% in vehicle; P=0.017); enhancement of the reparative process with up-regulated vascular endothelial growth factor, granulocyte macrophage colony-stimulating factor, and stromal-derived factor-1α gene expression; and increased M2 macrophages (67.2±10% versus 54.7±10.2% in vehicle; P=0.016). In long-term groups, increase in myocardial perfusion at the anterior infarct border was observed both on day-7 and day-60 cardiac magnetic resonance studies in ATMSCs-treated animals, compared to vehicle (87.9±28.7 versus 57.4±17.7 mL/min per gram at 7 days; P=0.034 and 99±22.6 versus 43.3±14.7 22.6 mL/min per gram at 60 days; P=0.0001, respectively). At day 60, higher vascular density was detected at the border zone in the ATMSCs-treated animals (118±18 versus 92.4±24.3 vessels/mm2 in vehicle; P=0.045). Cardiac magnetic resonance-measured left ventricular ejection fraction of left ventricular volumes was not different between groups at any time point.

CONCLUSIONS

In this porcine acute myocardial infarction model, allogeneic ATMSCs-based therapy was associated with increased cardioprotective and reparative mechanisms and with better cardiac magnetic resonance-measured perfusion. No effect on left ventricular volumes or ejection fraction was observed.

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.

Accuracy of Area at Risk Quantification by Cardiac Magnetic Resonance According to the Myocardial Infarction Territory

INTRODUCTION AND OBJECTIVES

Area at risk (AAR) quantification is important to evaluate the efficacy of cardioprotective therapies. However, postinfarction AAR assessment could be influenced by the infarcted coronary territory. Our aim was to determine the accuracy of T₂-weighted short tau triple-inversion recovery (T₂W-STIR) cardiac magnetic resonance (CMR) imaging for accurate AAR quantification in anterior, lateral, and inferior myocardial infarctions.

METHODS

Acute reperfused myocardial infarction was experimentally induced in 12 pigs, with 40-minute occlusion of the left anterior descending (n = 4), left circumflex (n = 4), and right coronary arteries (n = 4). Perfusion CMR was performed during selective intracoronary gadolinium injection at the coronary occlusion site (in vivo criterion standard) and, additionally, a 7-day CMR, including T₂W-STIR sequences, was performed. Finally, all animals were sacrificed and underwent postmortem Evans blue staining (classic criterion standard).

RESULTS

The concordance between the CMR-based criterion standard and T₂W-STIR to quantify AAR was high for anterior and inferior infarctions (r = 0.73; P = .001; mean error = 0.50%; limits = -12.68%-13.68% and r = 0.87; P = .001; mean error = -1.5%; limits = -8.0%-5.8%, respectively). Conversely, the correlation for the circumflex territories was poor (r = 0.21, P = .37), showing a higher mean error and wider limits of agreement. A strong correlation between pathology and the CMR-based criterion standard was observed (r = 0.84, P < .001; mean error = 0.91%; limits = -7.55%-9.37%).

CONCLUSIONS

T₂W-STIR CMR sequences are accurate to determine the AAR for anterior and inferior infarctions; however, their accuracy for lateral infarctions is poor. These findings may have important implications for the design and interpretation of clinical trials evaluating the effectiveness of cardioprotective therapies.

Major publications in the critical care pharmacotherapy literature: January-December 2014

PURPOSE

Nine recently published articles and one guideline with important implications for critical care pharmacy practice are summarized.

SUMMARY

The Critical Care Pharmacotherapy Literature Update (CCPLU) group includes more than 40 experienced critical care pharmacists across the United States. Group members monitor 29 peer-reviewed journals on an ongoing basis to identify literature relevant to pharmacy practice in the critical care setting. After evaluation by CCPLU group members, selected articles are chosen for summarization and distribution to group members nationwide based on applicability to practice, relevance, and study design and strength. Hundreds of relevant articles were evaluated by the group in 2014, of which 114 were summarized and disseminated to CCPLU group members. From among those 114 publications, 10 deemed to be of particularly high utility to the critical care practitioner were selected for inclusion in this review for their potential to change practice or reinforce current evidence-based practice. One of the selected articles presents updated recommendations on the management of patients with atrial fibrillation (AF); the other 9 address topics such as albumin replacement in patients with severe sepsis, use of enteral statins for acute respiratory distress syndrome, fibrinolysis for patients with intermediate-risk pulmonary embolism, the use of unfractionated heparin versus bivalirudin for primary percutaneous coronary intervention, and early protocol-based care for septic shock.

CONCLUSION

There were many important additions to the critical care pharmacotherapy literature in 2014, including a joint guideline for the management of AF and reports of clinical trials.

Early Intravenous Beta-Blockers in Patients With ST-Segment Elevation Myocardial Infarction Before Primary Percutaneous Coronary Intervention

BACKGROUND

The impact of intravenous (IV) beta-blockers before primary percutaneous coronary intervention (PPCI) on infarct size and clinical outcomes is not well established.

OBJECTIVES

This study sought to conduct the first double-blind, placebo-controlled international multicenter study testing the effect of early IV beta-blockers before PPCI in a general ST-segment elevation myocardial infarction (STEMI) population.

METHODS

STEMI patients presenting <12 h from symptom onset in Killip class I to II without atrioventricular block were randomized 1:1 to IV metoprolol (2 × 5-mg bolus) or matched placebo before PPCI. Primary endpoint was myocardial infarct size as assessed by cardiac magnetic resonance imaging (CMR) at 30 days. Secondary endpoints were enzymatic infarct size and incidence of ventricular arrhythmias. Safety endpoints included symptomatic bradycardia, symptomatic hypotension, and cardiogenic shock.

RESULTS

A total of 683 patients (mean age 62 ± 12 years; 75% male) were randomized to metoprolol (n = 336) or placebo (n = 346). CMR was performed in 342 patients (54.8%). Infarct size (percent of left ventricle [LV]) by CMR did not differ between the metoprolol (15.3 ± 11.0%) and placebo groups (14.9 ± 11.5%; p = 0.616). Peak and area under the creatine kinase curve did not differ between both groups. LV ejection fraction by CMR was 51.0 ± 10.9% in the metoprolol group and 51.6 ± 10.8% in the placebo group (p = 0.68). The incidence of malignant arrhythmias was 3.6% in the metoprolol group versus 6.9% in placebo (p = 0.050). The incidence of adverse events was not different between groups.

CONCLUSIONS

In a nonrestricted STEMI population, early intravenous metoprolol before PPCI was not associated with a reduction in infarct size. Metoprolol reduced the incidence of malignant arrhythmias in the acute phase and was not associated with an increase in adverse events. (Early-Beta blocker Administration before reperfusion primary PCI in patients with ST-elevation Myocardial Infarction [EARLY-BAMI]; EudraCT no: 2010-023394-19).

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.

QRS distortion in pre-reperfusion electrocardiogram is a bedside predictor of large myocardium at risk and infarct size (a METOCARD-CNIC trial substudy)

BACKGROUND

QRS distortion is an electrocardiographic (ECG) sign of severe ongoing ischemia in the setting of ST-segment elevation acute myocardial infarction (STEMI). We sought to evaluate the association between the degree of QRS distortion and myocardium at risk and final infarct size, measured by cardiac magnetic resonance (CMR).

METHODS

A total of 174 patients with a first anterior STEMI reperfused by primary angioplasty were prospectively recruited. Pre-reperfusion ECG was used to divide the study population into three groups according to the absence of QRS distortion (D0) or its presence in a single lead (D1) or in 2 or more contiguous leads (D2+). Myocardium at risk and infarct size were determined by CMR one week after STEMI. Multiple regression analysis was used to study the association of QRS distortion with myocardium at risk and infarct size, with adjustment for relevant clinical and ECG variables.

RESULTS

101 patients (58%) were in group D0, 30 (17%) in group D1, and 43 (25%) in group D2+. Compared with group D0, presence of QRS distortion (groups D2+ and D1) was associated with a significantly adjusted larger extent of myocardium at risk (group D2+: absolute increase 10.4%, 95% CI 6.1-14.8%, p<0.001; group D1: absolute increase 3.3%, 95% CI 1.3-7.9%, p=0.157) and larger infarct size (group D2+: absolute increase 10.1%, 95% CI 5.5-14.7%, p<0.001; group D1: absolute increase 4.9%, 95% CI 0.08-9.8%, p=0.046).

CONCLUSIONS

Distortion in the terminal portion of the QRS complex on pre-reperfusion ECG in two or more leads is independently associated with larger myocardium at risk and infarct size in the setting of primary angioplasty-reperfused anterior STEMI. QRS distortion in only one lead is independently associated with larger infarct size in this setting. Our findings suggest that QRS distortion analysis could be included in risk-stratification of patients presenting with anterior STEMI.

Effective components of Panax quinquefolius and Corydalis tuber protect the myocardium by inhibiting platelet activation and improving the hypercoagulable state

The aim of the present study was to investigate the effects of extract of Panax quinquefolius and Corydalis tuber (EPC) on platelet activation and the hypercoagulable state in rats with acute myocardial infarction (AMI). The MI model in Wistar rats was induced by coronary artery ligation. Sham surgery was performed as a control. The surviving rats that underwent MI surgery were divided into control (administered normal saline), metoprolol (9 mg/kg) and low-, moderate- and high-dose EPC groups (0.54, 1.08 g/kg and 2.16 g/kg, respectively). Saline, metoprolol and EPC were administered by gastrogavage for two consecutive weeks. The morphological changes of the myocardium were assessed by hematoxylin and eosin and nitroblue tetrazolium staining. Serum von Willebrand factor (vWF), D-dimer (DD), platelet membrane glycoproteins IIb-IIIa (GPIIb-IIIa) and CD62P levels were assessed using enzyme-linked immunosorbent assay. EPC attenuated the pathological changes of the myocardium. High-dose EPC decreased the serum concentration of vWF when compared with control group. Moderate and high doses of EPC decreased the DD and GPIIb-IIIa levels, and the CD62P level was gradually decreased with EPC dose escalation. The results therefore demonstrated that EPC protects the myocardium by inhibiting platelet activation and improving the hypercoagulable state in a rat model of AMI.

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.

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.

Health and cost benefits associated with the use of metoprolol in heart attack patients

Heart attack (myocardial infarction) is a highly prevalent entity worldwide. Widespread implementation of reperfusion strategies has dramatically reduced the mortality associated with infarction. Paradoxically, the mortality reduction has significantly increased the incidence of chronic heart failure (HF). Treatment of HF, once present, represents a huge socioeconomic burden on individuals and healthcare systems. The possibility of preventing rather than treating post-infarction HF would be of paramount importance. Given that infarct size is the main determinant of adverse post-infarction outcomes (including chronic HF), therapies able to reduce infarct size are needed. The single administration of intravenous metoprolol before reperfusion has been recently shown to reduce infarct size and reduce the cases of chronic HF in a proof-of-concept trial. If confirmed in larger trials, this low-cost therapy is expected to have a major health and socioeconomic impact.

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.

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.

Myocardial reperfusion injury: looking beyond primary PCI

Coronary heart disease (CHD) is the leading cause of death and disability in Europe. For patients presenting with an acute ST-segment elevation myocardial infarction (STEMI), timely myocardial reperfusion using either thrombolytic therapy or primary percutaneous coronary intervention (PPCI) is the most effective therapy for limiting myocardial infarct (MI) size, preserving left-ventricular systolic function and reducing the onset of heart failure. Despite this, the morbidity and mortality of STEMI patients remain significant, and novel therapeutic interventions are required to improve clinical outcomes in this patient group. Paradoxically, the process of myocardial reperfusion can itself induce cardiomyocyte death-a phenomenon which has been termed 'myocardial reperfusion injury' (RI), the irreversible consequences of which include microvascular obstruction and myocardial infarction. Unfortunately, there is currently no effective therapy for preventing myocardial RI in STEMI patients making it an important residual target for cardioprotection. Previous attempts to translate cardioprotective therapies (antioxidants, calcium-channel blockers, and anti-inflammatory agents) for reducing RI into the clinic, have been unsuccessful. An improved understanding of the pathophysiological mechanisms underlying RI has resulted in the identification of several promising mechanical (ischaemic post-conditioning, remote ischaemic pre-conditioning, therapeutic hypothermia, and hyperoxaemia), and pharmacological (atrial natriuretic peptide, cyclosporin-A, and exenatide) therapeutic strategies, for preventing myocardial RI, many of which have shown promise in initial proof-of-principle clinical studies. In this article, we review the pathophysiology underlying myocardial RI, and highlight the potential therapeutic interventions which may be used in the future to prevent RI and improve clinical outcomes in patients with CHD.