Meta-analysis of the effects of ischemic postconditioning on structural pathology in ST-segment elevation acute myocardial infarction

Coronary microvascular obstruction and dysfunction in patients with acute myocardial infarction

Despite prompt epicardial recanalization in patients presenting with ST-segment elevation myocardial infarction (STEMI), coronary microvascular obstruction and dysfunction (CMVO) is still fairly common and is associated with poor prognosis. Various pharmacological and mechanical strategies to treat CMVO have been proposed, but the positive results reported in preclinical and small proof-of-concept studies have not translated into benefits in large clinical trials conducted in the modern treatment setting of patients with STEMI. Therefore, the optimal management of these patients remains a topic of debate. In this Review, we appraise the pathophysiological mechanisms of CMVO, explore the evidence and provide future perspectives on strategies to be implemented to reduce the incidence of CMVO and improve prognosis in patients with STEMI.

Effects of Remote Ischaemic Conditioning in Stable and Unstable Angina Patients Undergoing Percutaneous Coronary Intervention: A Systematic Review and Meta-Analysis

AIM

Type 4a myocardial infarction (T4aMI), defined as myocardial injury associated with percutaneous coronary intervention (PCI), is associated with a poor prognosis and there is conflicting evidence regarding the effectiveness of remote ischaemic conditioning (RIC) in its prevention. This review aimed to determine the effect of RIC on stable and unstable angina patients.

METHOD

A systematic review was conducted in PubMed and Central database. Outcome measures were: changes in peak troponin, creatine kinase myocardial band (CKMB), C-reactive protein (CRP) level, incidence of T4aMI, and major adverse cardiovascular event (MACE). Data were meta-analysed and reported as standardised mean difference (SMD) and odds ratio (OR). Risk of bias was assessed with the Risk of Bias 2 (RoB2) tool.

RESULTS

Fifteen studies with no significant risk of bias were included. Peak troponin level was reduced in the RIC group, particularly after excluding a study with low statin use, while CKMB and CRP levels resulted in a non-significant SMD between the groups. The incidence of T4aMI was significantly lower in the intervention group (OR 0.714; p=0.026); this finding was also seen in subgroups of elective PCI, pre-conditioning, and high statin use. Incidence of MACE also only reached statistically significant protective effects with OR <1 in similar subgroups. No substantial heterogeneity was found and the funnel plot did not show publication bias.

CONCLUSION

Remote ischaemic conditioning in elective PCI patients has been proven to be potentially beneficial in reducing peak troponin levels and risk of T4aMI and MACE.

Signaling Pathways Involved in Myocardial Ischemia-Reperfusion Injury and Cardioprotection: A Systematic Review of Transcriptomic Studies in Sus scrofa

Myocardial damage in acute myocardial infarctions (AMI) is primarily the result of ischemia−reperfusion injury (IRI). Recognizing the timing of transcriptional events and their modulation by cardioprotective strategies is critical to address the pathophysiology of myocardial IRI. Despite the relevance of pigs for translational studies of AMI, only a few have identified how transcriptomic changes shape cellular signaling pathways in response to injury. We systematically reviewed transcriptomic studies of myocardial IRI and cardioprotection in Sus scrofa. Gene expression datasets were analyzed for significantly enriched terms using the Enrichr analysis tool, and statistically significant results (adjusted p-values of <0.05) for Signaling Pathways, Transcription Factors, Molecular Functions, and Biological Processes were compared between eligible studies to describe how these dynamic changes transform the myocardium from an injured and inflamed tissue into a scar. Then, we address how cardioprotective interventions distinctly modulate the myocardial transcriptome and discuss the implications of uncovering gene regulatory networks for cardiovascular pathologies and translational applications.

The effect of ischaemic postconditioning on mucosal integrity and function in equine jejunal ischaemia

BACKGROUND

Ischaemic postconditioning (IPoC) has been shown to ameliorate ischaemia reperfusion injury in different species and tissues.

OBJECTIVES

To assess the feasibility of IPoC in equine small intestinal ischaemia and to assess its effect on histomorphology, electrophysiology and paracellular permeability.

STUDY DESIGN

Randomised in vivo experiment.

METHODS

Experimental jejunal ischaemia was induced for 90 min in horses under general anaesthesia. In the control group (C; n = 7), the jejunum was reperfused without further intervention. In the postconditioning group (IPoC; n = 7), reocclusion was implemented following release of ischaemia by clamping the mesenteric vessels in three cycles of 30 seconds. This was followed by 120 minutes of reperfusion in both groups. Intestinal microperfusion and oxygenation was measured during IPoC using spectrophotometry and Doppler flowmetry. Histomorphology and histomorphometry of the intestinal mucosa were assessed. Furthermore, electrophysiological variables and unidirectional flux rates of ³ H-mannitol were determined in Ussing chambers. Western blot analysis was performed to determine the tight junction protein levels of claudin-1, claudin-2 and occludin in the intestinal mucosa. Comparisons between the groups and time points were performed using a two-way repeated measures analysis of variance (ANOVA) or non-parametric statistical tests for the ordinal and not normally distributed data (significance P < .05).

RESULTS

IPoC significantly reduced intestinal microperfusion during all clamping cycles yet affected oxygen saturation only during the first cycle. After reperfusion, Group IPoC showed significantly less mucosal villus denudation (mean difference 21.5%, P = .02) and decreased mucosal-to-serosal flux rates (mean difference 15.2 nM/cm² /h, P = .007) compared to Group C. There were no significant differences between the groups for the other tested variables.

MAIN LIMITATIONS

Small sample size, long-term effects were not investigated.

CONCLUSIONS

Following IPoC, the intestinal mucosa demonstrated significantly less villus denudation and paracellular permeability compared to the untreated control group, possibly indicating a protective effect of IPoC on ischaemia reperfusion injury.

Perioperative Cardioprotection: Clinical Implications

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

Platelets in cardiac ischaemia/reperfusion injury: a promising therapeutic target

Acute myocardial infarction (AMI) is the single leading cause of mortality and morbidity worldwide. A key component of AMI therapy is the timely reopening of occluded vessels to prevent further ischaemic damage to the myocardium. However, reperfusion of the ischaemic myocardium can itself trigger reperfusion injury causing up to 50% of the overall infarct size. In recent years, considerable research has been devoted to understanding the pathogenesis of ischaemia/reperfusion (I/R) injury and platelets have emerged as a major contributing factor. This review summarizes the role of platelets in the pathogenesis of I/R injury and highlights the potential of platelet-directed therapeutics to minimize cardiac I/R injury. Activated platelets infiltrate specifically into the ischaemic/reperfused myocardium and contribute to I/R injury by the formation of microthrombi, enhanced platelet-leucocyte aggregation, and the release of potent vasoconstrictor and pro-inflammatory molecules. This review demonstrates the benefits of platelet inhibition beyond their well-described anti-thrombotic effect and highlights the direct cardioprotective role of anti-platelet drugs. In particular, the inhibition of COX, the P2Y12 receptor and the GPIIb/IIIa receptor has demonstrated the potential to attenuate I/R injury. Moreover, targeting of drug candidates or regenerative cells to the activated platelets accumulated within the ischaemic/reperfused myocardium shows remarkable potential to protect the myocardium from I/R injury. Overall, activated platelets play a key role in the pathogenesis of I/R injury. Their direct inhibition as well as their use as epitopes for site-directed therapy is a unique and promising therapeutic approach for the prevention of I/R injury and ultimately the preservation of cardiac function.

The Role of Platelets in Ischemic Conditioning

Ischemic heart disease (IHD) is one of the leading causes of death and disability worldwide. Platelets, as the main regulators of hemostasis, are major players in acute myocardial ischemia/reperfusion injury (IRI). Additionally, platelets are modified by endogenous cardioprotective strategies such as ischemic preconditioning, postconditioning, and remote ischemic conditioning. In this article, we provide an overview of the functionional role of platelets in acute myocardial IRI, and highlight their potential as targets for cardioprotection to improve health outcomes in patients with IHD.