A review of strategies for infarct size reduction during acute myocardial infarction

Platelet Reactivity Was Not Associated with Infarct Size after Primary Percutaneous Coronary Intervention

Potent antiplatelet therapy after primary percutaneous coronary intervention (PCI) has the potential to reduce infarct size. This study analyzed the association between on-treatment platelet reactivity and myocardial infarct size in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary PCI. In this single-center, retrospective study, 253 patients who underwent primary PCI for STEMI were divided into two groups according to platelet reactivity measurements (53 patients in the high platelet reactivity [HPR] group and 200 in the non-HPR group). Technetium Tc-99m tetrofosmin single-photon emission computed tomography (SPECT) was performed before hospital discharge. We measured the infarct size using SPECT imaging and serial cardiac biomarker levels, and compared the infarct sizes of each group. The patients with HPR were older (65.5±13.2 vs. 60.6±12.1 years, p=0.011) than the patients with non-HPR. On the other hand, the non-HPR group had a higher incidence of smoking (26.4% vs. 51.0%, p=0.001) than the HPR group. Infarct size was similar between the two groups (22.6±17.3% vs. 24.8±17.7%, p=0.416). Multivariate analysis revealed that onset to balloon time >240 min (odds ratio [OR]=1.92; 95% confidence interval [CI]=1.08-3.40; p=0.025) and anterior infarction (OR=5.28; 95% CI=3.05-9.14; p<0.001) were independent predictors of large (>22%) infarct size. HPR was not a predictor of infarct size assessed by SPECT. The two groups also showed analogous cumulative creatinine kinase-myocardial band and troponin T levels. In conclusion, compared to non-HPR, HPR showed no significant association with myocardial infarct size measured by SPECT imaging in early phase of MI.

Augmented glycaemic gap is a marker for an increased risk of post-infarct left ventricular systolic dysfunction

Background

Left ventricular systolic dysfunction (LVSD) occurs frequently after acute ST-segment elevation myocardial infarction (STEMI). The predisposing factors and underlying mechanism of post-infarct LVSD are not fully understood. The present study mainly investigated the correlation between glycaemic gap, a novel index of stress-induced hyperglycaemia (SIH), and post-infarct LVSD.

Methods

A total of 274 first STEMI patients were enrolled in this cross-sectional study. Transthoracic echocardiography was performed within 48 h after admission and at 6 months after discharge to obtain left ventricular ejection fraction (LVEF). The change in LVEF was calculated as LVEF at 6 months after discharge minus baseline LVEF. Additionally, post-infarct LVSD was defined as LVEF ≤ 50%. Most importantly, glycaemic gap was calculated as admission blood glucose (ABG) minus the estimated average glucose over the previous 3 months.

Results

In patients without diabetes mellitus (DM), multivariate linear regression analysis revealed that both glycaemic gap (Beta = − 1.214, 95% CI − 1.886 to − 0.541, p < 0.001) and ABG (Beta = − 1.124, 95% CI − 1.795 to − 0.453, p = 0.001) were associated with change in LVEF. In DM patients, only glycaemic gap was still associated with change in LVEF, although this association was not observed in univariate linear regression analysis. Regarding the association between SIH and post-infarct LVSD, multivariate logistic regression analysis revealed that both glycaemic gap (OR = 1.490, 95% CI 1.043 to 2.129, p = 0.028) and ABG (OR = 1.600, 95% CI 1.148 to 2.229, p = 0.005) were associated with an increased risk of having post-infarct LVSD in non-DM patients. However, after multivariate adjustment in DM patients, only glycaemic gap (OR = 1.399, 95% CI 1.021 to 1.919, p = 0.037) remained associated with an increased risk of having post-infarct LVSD. Furthermore, the predictive value of glycaemic gap for post-infarct LVSD was not inferior to ABG in non-DM patients (p = 0.499), and only glycaemic gap, instead of ABG, could significantly predict post-infarct LVSD in DM patients (AUC = 0.688, 95% CI 0.591 to 0.774, p = 0.002).

Conclusions

Glycaemic gap was strongly associated with a change in LVEF and an increased risk of having post-infarct LVSD in patients following STEMI. In STEMI patients with DM, glycaemic gap could provide more valuable information than ABG in identifying patients at high risk of developing post-infarct LVSD.

Cellular and molecular approaches to enhance myocardial recovery after myocardial infarction

Reperfusion therapy has resulted in significant improvement in post-myocardial infarction morbidity and mortality in over the last 4 decades. Nonetheless, it is well recognized that simply restoring patency of the epicardial artery may not stop or reverse damage at microvascular level, and myocardial salvage is often suboptimal. Numerous efforts have been undertaken to elucidate the mechanisms underlying extensive myonecrosis to facilitate the discovery of therapies to provide additional and incremental benefits over current therapeutic pathways. To date, conclusively effective strategies to promote myocardial recovery have not yet been established. Novel approaches are investigating the foundational cellular and molecular bases of myocardial ischemia and irreversible injury. Herein, we review the emerging concepts and proposed therapies that may improve myocardial protection and reduce infarct size. We examine the preclinical and clinical evidence for reduced infarct size with these strategies, including anti-inflammatory agents, intracellular ion channel modulators, agents affecting the reperfusion injury salvage kinase (RISK) and nitric oxide signaling pathways, modulators of mitochondrial function, anti-apoptotic agents, and stem cell and gene therapy. We review the potential reasons of failures to date and the potential for new strategies to further promote myocardial recovery and improve prognosis.

Synthetic CpG oligonucleotides induce a genetic profile ameliorating murine myocardial I/R injury

We previously demonstrated that pre‐conditioning with CpG oligonucleotide (ODN) 1668 induces quick up‐regulation of gene expression 3 hours post‐murine myocardial ischaemia/reperfusion (I/R) injury, terminating inflammatory processes that sustain I/R injury. Now, performing comprehensive microarray and biocomputational analyses, we sought to further enlighten the “black box” beyond these first 3 hours. C57BL/6 mice were pretreated with either CpG 1668 or with control ODN 1612, respectively. Sixteen hours later, myocardial ischaemia was induced for 1 hour in a closed‐chest model, followed by reperfusion for 24 hours. RNA was extracted from hearts, and labelled cDNA was hybridized to gene microarrays. Data analysis was performed with BRB ArrayTools and Ingenuity Pathway Analysis. Functional groups mediating restoration of cellular integrity were among the top up‐regulated categories. Genes known to influence cardiomyocyte survival were strongly induced 24 hours post‐I/R. In contrast, proinflammatory pathways were down‐regulated. Interleukin‐10, an upstream regulator, suppressed specifically selected proinflammatory target genes at 24 hours compared to 3 hours post‐I/R. The IL1 complex is supposed to be one regulator of a network increasing cardiovascular angiogenesis. The up‐regulation of numerous protective pathways and the suppression of proinflammatory activity are supposed to be the genetic correlate of the cardioprotective effects of CpG 1668 pre‐conditioning.

Diallyl trisulfide exerts cardioprotection against myocardial ischemia-reperfusion injury in diabetic state, role of AMPK-mediated AKT/GSK-3β/HIF-1α activation

Diallyl trisulfide (DATS), the major active ingredient in garlic, has been reported to confer cardioprotective effects. However, its effect on myocardial ischemia-reperfusion (MI/R) injury in diabetic state and the underlying mechanism are still unknown. We hypothesize that DATS reduces MI/R injury in diabetic state via AMPK-mediated AKT/GSK-3β/HIF-1α activation. Streptozotocin-induced diabetic rats received MI/R surgery with or without DATS (20mg/kg) treatment in the presence or absence of Compound C (Com.C, an AMPK inhibitor, 0.25mg/kg) or LY294002 (a PI3K inhibitor, 5mg/kg). We found that DATS significantly improved heart function and reduced myocardial apoptosis. Additionally, in cultured H9c2 cells, DATS (10μM) also attenuated simulated ischemia-reperfusion injury. We found that AMPK and AKT/GSK-3β/HIF-1α signaling were down-regulated under diabetic condition, while DATS markedly increased the phosphorylation of AMPK, ACC, AKT and GSK-3β as well as HIF-1α expression in MI/R-injured myocardium. However, these protective actions were all blunted by Com.C administration. Additionally, LY294002 abolished the stimulatory effect of DATS on AKT/GSK-3β/HIF-1α signaling without affecting AMPK signaling. While 2-methoxyestradiol (a HIF-1α inhibitor) reduced HIF-1α expression without affecting AKT/GSK-3β signaling. Taken together, these data showed that DATS protected against MI/R injury in diabetic state by attenuating cellular apoptosis via AMPK-mediated AKT/GSK-3β/HIF-1α signaling. Its cardioprotective effect deserves further study.