The coronary circulation in cardioprotection: more than just one confounder

Sex-specific differences in the mechanisms for enhanced thromboxane A2-mediated vasoconstriction in adult offspring exposed to prenatal hypoxia

BACKGROUND

Prenatal hypoxia, a common pregnancy complication, leads to impaired cardiovascular outcomes in the adult offspring. It results in impaired vasodilation in coronary and mesenteric arteries of the adult offspring, due to reduced nitric oxide (NO). Thromboxane A2 (TxA2) is a potent vasoconstrictor increased in cardiovascular diseases, but its role in the impact of prenatal hypoxia is unknown. To prevent the risk of cardiovascular disease by prenatal hypoxia, we have tested a maternal treatment using a nanoparticle-encapsulated mitochondrial antioxidant (nMitoQ). We hypothesized that prenatal hypoxia enhances vascular TxA2 responses in the adult offspring, due to decreased NO modulation, and that this might be prevented by maternal nMitoQ treatment.

METHODS

Pregnant Sprague-Dawley rats received a single intravenous injection (100 µL) of vehicle (saline) or nMitoQ (125 µmol/L) on gestational day (GD)15 and were exposed to normoxia (21% O2) or hypoxia (11% O2) from GD15 to GD21 (term = 22 days). Coronary and mesenteric arteries were isolated from the 4-month-old female and male offspring, and vasoconstriction responses to U46619 (TxA2 analog) were evaluated using wire myography. In mesenteric arteries, L-NAME (pan-NO synthase (NOS) inhibitor) was used to assess NO modulation. Mesenteric artery endothelial (e)NOS, and TxA2 receptor expression, superoxide, and 3-nitrotyrosine levels were assessed by immunofluorescence.

RESULTS

Prenatal hypoxia resulted in increased U46619 responsiveness in coronary and mesenteric arteries of the female offspring, and to a lesser extent in the male offspring, which was prevented by nMitoQ. In females, there was a reduced impact of L-NAME in mesenteric arteries of the prenatal hypoxia saline-treated females, and reduced 3-nitrotyrosine levels. In males, L-NAME increased U46619 responses in mesenteric artery to a similar extent, but TxA2 receptor expression was increased by prenatal hypoxia. There were no changes in eNOS or superoxide levels.

CONCLUSIONS

Prenatal hypoxia increased TxA2 vasoconstrictor capacity in the adult offspring in a sex-specific manner, via reduced NO modulation in females and increased TP expression in males. Maternal placental antioxidant treatment prevented the impact of prenatal hypoxia. These findings increase our understanding of how complicated pregnancies can lead to a sex difference in the programming of cardiovascular disease in the adult offspring.

Lutein suppresses ferroptosis of cardiac microvascular endothelial cells via positive regulation of IRF in cardiac hypertrophy

Cardiac microvascular dysfunction contributes to cardiac hypertrophy (CH) and can progress to heart failure. Lutein is a carotenoid with various pharmacological properties, such as anti-apoptotic, anti-inflammatory, and antioxidant effects. Limited research has been conducted on the effects of lutein on pressure overload-induced CH. Studies have shown that CH is accompanied by ferroptosis in the cardiac microvascular endothelial cells (CMECs). This study aimed to investigate the effect of lutein on ferroptosis of CMECs in CH. The transcription factor interferon regulatory factor (IRF) is associated with immune system function, tumor suppression, and apoptosis. The results of this study suggested that pressure overload primarily inhibits IRF expression, resulting in endothelial ferroptosis. Administration of lutein increased the expression of IRF, providing protection to endothelial cells during pressure overload. IRF silencing downregulated solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) expression, leading to the induction of ferroptosis in CMECs. Lutein supplementation suppressed endothelial ferroptosis by upregulating IRF. These data suggest that IRF may function as a transcription factor for SLC7A11 and that lutein represses ferroptosis in CMECs by upregulating IRF expression. Therefore, targeting IRF may be a promising therapeutic strategy for effective cardioprotection in patients with CH and heart failure.

Chronic remote ischemic conditioning treatment in patients with chronic stable angina (EARLY-MYO-CSA): a randomized, controlled proof-of-concept trial

BACKGROUND

Chronic remote ischemic conditioning (CRIC) has been shown to improve myocardial ischemia in experimental animal studies; however, its effectiveness in patients with chronic stable angina (CSA) has not been investigated. We conducted a proof-of-concept study to investigate the efficacy and safety of a six-month CRIC treatment in patients with CSA.

METHODS

The EARLY-MYO-CSA trial was a prospective, randomized, controlled trial evaluating the CRIC treatment in patients with CSA with persistent angina pectoris despite receiving ≥ 3-month guideline-recommended optimal medical therapy. The CRIC and control groups received CRIC (at 200 mmHg) or sham CRIC (at 60 mmHg) intervention for 6 months, respectively. The primary endpoint was the 6-month change of myocardial flow reserve (MFR) on single-photon emission computed tomography. The secondary endpoints were changes in rest and stress myocardial blood flow (MBF), angina severity according to the Canadian Cardiovascular Society (CCS) classification, the Seattle Angina Questionnaire (SAQ), and a 6-min walk test (6-MWT).

RESULTS

Among 220 randomized CSA patients, 208 (105 in the CRIC group, and 103 in the control group) completed the treatment and endpoint assessments. The mean change in MFR was significantly greater in the CRIC group than in the control group (0.27 ± 0.38 vs. - 0.04 ± 0.25; P < 0.001). MFR increased from 1.33 ± 0.48 at baseline to 1.61 ± 0.53 (P < 0.001) in the CRIC group; however, a similar increase was not seen in the control group (1.35 ± 0.45 at baseline and 1.31 ± 0.44 at follow-up, P = 0.757). CRIC treatment, when compared with controls, demonstrated improvements in angina symptoms assessed by CCS classification (60.0% vs. 14.6%, P < 0.001), all SAQ dimensions scores (P < 0.001), and 6-MWT distances (440 [400-523] vs. 420 [330-475] m, P = 0.016). The incidence of major adverse cardiovascular events was similar between the groups.

CONCLUSIONS

CSA patients benefit from 6-month CRIC treatment with improvements in MFR, angina symptoms, and exercise performance. This treatment is well-tolerated and can be recommended for symptom relief in this clinical population.

TRIAL REGISTRATION

[chictr.org.cn], identifier [ChiCTR2000038649].

Endothelial ILK induces cardioprotection by preventing coronary microvascular dysfunction and endothelial-to-mesenchymal transition

Endothelial dysfunction is an early event in coronary microvascular disease. Integrin-linked kinase (ILK) prevents endothelial nitric oxide synthase (eNOS) uncoupling and, thus, endothelial dysfunction. However, the specific role of endothelial ILK in cardiac function remains to be fully elucidated. We hypothesised that endothelial ILK plays a crucial role in maintaining coronary microvascular function and contractile performance in the heart. We generated an endothelial cell-specific ILK conditional knock-out mouse (ecILK cKO) and investigated cardiovascular function. Coronary endothelial ILK deletion significantly impaired cardiac function: ejection fraction, fractional shortening and cardiac output decreased, whilst left ventricle diastolic internal diameter decreased and E/A and E/E' ratios increased, indicating not only systolic but also diastolic dysfunction. The functional data correlated with extensive extracellular matrix remodelling and perivascular fibrosis, indicative of adverse cardiac remodelling. Mice with endothelial ILK deletion suffered early ischaemic-like events with ST elevation and transient increases in cardiac troponins, which correlated with fibrotic remodelling. In addition, ecILK cKO mice exhibited many features of coronary microvascular disease: reduced cardiac perfusion, impaired coronary flow reserve and arterial remodelling with patent epicardial coronary arteries. Moreover, endothelial ILK deletion induced a moderate increase in blood pressure, but the antihypertensive drug Losartan did not affect microvascular remodelling whilst only partially ameliorated fibrotic remodelling. The plasma miRNA profile reveals endothelial-to-mesenchymal transition (endMT) as an upregulated pathway in endothelial ILK conditional KO mice. Our results show that endothelial cells in the microvasculature in endothelial ILK conditional KO mice underwent endMT. Moreover, endothelial cells isolated from these mice and ILK-silenced human microvascular endothelial cells underwent endMT, indicating that decreased endothelial ILK contributes directly to this endothelial phenotype shift. Our results identify ILK as a crucial regulator of microvascular endothelial homeostasis. Endothelial ILK prevents microvascular dysfunction and cardiac remodelling, contributing to the maintenance of the endothelial cell phenotype.

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

BACKGROUND

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

METHODS/DESIGN

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

CONCLUSIONS

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

Investigation of the protective mechanism of leonurine against acute myocardial ischemia by an integrated metabolomics and network pharmacology strategy

Background

Leonurus japonicus Houtt has an obvious efficacy on cardiovascular diseases. As the most representative component in the herb, leonurine has attracted increasing attention for its potential in myocardial ischemia. However, its protective mechanism against myocardial ischemia remains incompletely elucidated.

Objectives

The present study aimed to reveal the potential mechanism of leonurine in acute myocardial ischemia using a strategy combining metabolomics and network pharmacology.

Methods

First, a metabolomics method was proposed to identify the differential metabolites of plasma in rats. Then, network pharmacology was performed to screen candidate targets of leonurine against acute myocardial ischemia. A compound-reaction-enzyme-gene network was thus constructed with the differential metabolites and targets. Finally, molecular docking was carried out to predict the binding capability of leonurine with key targets.

Results

A total of 32 differential metabolites were identified in rat plasma, and 16 hub genes were detected through network pharmacology. According to the results of compound-reaction-enzyme-gene network and molecular docking, what was screened included six key targets (GSR, CYP2C9, BCHE, GSTP1, TGM2, and PLA2G2A) and seven differential metabolites (glycerylphosphorylcholine, lysophosphatidylcholine, choline phosphate, linoleic acid, 13-HpODE, tryptophan and glutamate) with four important metabolic pathways involved: glycerophospholopid metabolism, linoleic acid metabolism, tryptophan metabolism and glutamate metabolism. Among them, glycerophospholipid and tryptophan metabolism were shown to be important, since the regulation of leonurine on these two pathways was also observed in our previous metabolomics study conducted on clinical hyperlipidemia patients.

Conclusion

This is the first study of its kind to reveal the underlying mechanism of leonurine against acute myocardial ischemia through a strategy combining metabolomics and network pharmacology, which provides a valuable reference for the research on its future application.

Do collaterals visualized on coronary angiography impact left ventricle ejection fraction among Asian Indians presenting with acute coronary syndrome?-The Deucalion Study

BACKGROUND

The coronary collaterals have been ascribed as a potential alternative source of myocardial perfusion to the extent that some suggest it as a "natural bypass"! We proposed to evaluate the impact of the extent of collaterals on left ventricle ejection fraction among Asian Indians presenting with acute coronary syndrome.

METHODS

This was a retrospective, all-comers study performed on consecutive 3614 patients presenting with the acute coronary syndrome. Angiograms were evaluated for collaterals graded according to Rentrop's classification among group A (grades 0 and 1) and group B (grades 2 and 3) collaterals.

RESULTS

Patients were matched for traditional cardiovascular risk factors in groups A and B as well as for ST elevation myocardial infarction and non-ST elevation myocardial infarction subgroups in both the groups. Grades 2 and 3 collaterals were significantly (P = 0.04) higher in patients with non-ST elevation myocardial infarction-266/1319 (20.17%), as compared to ST elevation myocardial infarction-group 400/2295 (17.43%). Left ventricle ejection fraction on presentation was better preserved in group A as compared to group B in those with double-vessel disease and triple-vessel disease patients with non-ST elevation myocardial infarction, whereas it was better in single-vessel disease and triple-vessel disease patients with ST elevation myocardial infarction. The inverse correlation (r = -0.111, P = 0.000) existed between left ventricle ejection fraction and grades of collaterals.

CONCLUSION

Patients with the single-vessel disease were more likely to have poor coronary collateral as compared to double-vessel disease/triple-vessel disease. Despite higher grade coronary collateral among Asian Indians presenting with acute coronary syndrome, both non-ST elevation myocardial infarction and ST elevation myocardial infarction patients with triple-vessel disease had significantly lower left ventricle ejection fraction. This paradoxically brings out worse left ventricle ejection fraction on presentation in those with double-vessel disease and triple-vessel disease with ST elevation myocardial infarction and single-vessel disease and triple-vessel disease with ST elevation myocardial infarction despite higher grade of coronary collateral representing as "Asian Indian Paradox" in our cohort.

N-terminal pro-brain natriuretic peptide and coronary collateral formation in patients undergoing primary percutaneous coronary intervention

There is insufficient information on the relationship between the N-terminal pro-brain natriuretic peptide (NT-proBNP) level and collateral circulation (CC) formation after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction. We analyzed 857 patients who underwent primary PCI. The serum NT-proBNP levels were measured on the day of admission, and the CC was scored according to Rentrop’s classification. Log-transformed NT-proBNP levels were significantly higher in patients with good CC compared to those with poor CC (6.13 ± 2.01 pg/mL versus 5.48 ± 1.97 pg/mL, p < 0.001). The optimum cutoff value of log NT-proBNP for predicting CC was 6.04 pg/mL. Log NT-proBNP ≥ 6.04 pg/mL (odds ratio 2.23; 95% confidence interval 1.51–3.30; p < 0.001) was an independent predictor of good CC. CC development was higher in patients with a pre-TIMI flow of 0 or 1 than those with a pre-TIMI flow of 2 or 3 (22.6% versus 8.8%, p = 0.001). The incidence of left ventricular (LV) dysfunction (< 50%) was greater in patients with a pre-TIMI flow of 0 or 1 (49.8% versus 35.5%, p < 0.001). The release of NT-proBNP was greater in patients with LV dysfunction (34.3% versus 15.6%, p < 0.001). The incidence of good CC was greater in patients with log NT-proBNP levels ≥ 6.04 pg/ml (16.8% versus 26.2%, p = 0.003). The association between NT-proBNP and collateral formation was not influenced by pre-TIMI flow and LV function. NT-proBNP appears to reflect the degree of collateral formation in the early phase of STEMI and might have a new role as a useful surrogate biomarker for collateral formation in patients undergoing primary PCI.

The Rationale of Neprilysin Inhibition in Prevention of Myocardial Ischemia-Reperfusion Injury during ST-Elevation Myocardial Infarction

During the last three decades, timely myocardial reperfusion using either thrombolytic therapy or primary percutaneous intervention (pPCI) has allowed amazing improvements in outcomes with a more than halving in 1-year ST-elevation myocardial infarction (STEMI) mortality. However, mortality and left ventricle (LV) remodeling remain substantial in these patients. As such, novel therapeutic interventions are required to reduce myocardial infarction size, preserve LV systolic function, and improve survival in reperfused-STEMI patients. Myocardial ischemia-reperfusion injury (MIRI) prevention represents the main goal to reach in order to reduce STEMI mortality. There is currently no effective therapy for MIRI prevention in STEMI patients. A significant reason for the weak and inconsistent results obtained in this field may be the presence of multiple, partially redundant, mechanisms of cell death during ischemia-reperfusion, whose relative importance may depend on the conditions. Therefore, it is always more recognized that it is important to consider a "multi-targeted cardioprotective therapy", defined as an additive or synergistic cardioprotective agents or interventions directed to distinct targets with different timing of application (before, during, or after pPCI). Given that some neprilysin (NEP) substrates (natriuretic peptides, angiotensin II, bradykinin, apelins, substance P, and adrenomedullin) exert a cardioprotective effect against ischemia-reperfusion injury, it is conceivable that antagonism of proteolytic activity by this enzyme may be considered in a multi-targeted strategy for MIRI prevention. In this review, by starting from main pathophysiological mechanisms promoting MIRI, we discuss cardioprotective effects of NEP substrates and the potential benefit of NEP pharmacological inhibition in MIRI prevention.

NAD+ administration decreases microvascular damage following cardiac ischemia/reperfusion by restoring autophagic flux

Microvascular damage is a key pathological change in myocardial ischemia/reperfusion (I/R) injury. Using a rat model of myocardial I/R, our current study has provided the first evidence that nicotinamide adenine dinucleotide (NAD⁺) administration can significantly attenuate myocardial I/R-induced microvascular damage, including reduced regional blood perfusion, decreased microvessel density and integrity, and coronary microvascular endothelial cells (CMECs) injury. In studies with primary cultured CMECs under hypoxia/reoxygenation (HR) and a rat model of I/R, our results suggested that the protective effect of NAD⁺ on CMECs exposed to HR or I/R is at least partially mediated by the NAD⁺-induced restoration of autophagic flux, especially lysosomal autophagy: NAD⁺ treatment markedly induced transcription factor EB (TFEB) activation and attenuated lysosomal dysfunction in the I/R or HR-exposed cells. Collectively, our study has provided the first in vivo and in vitro evidence that NAD⁺ significantly rescued the impaired autophagic flux and cell apoptosis that was induced by I/R in rat CMECs, which is mediated in part through the action of TFEB-mediated lysosomal autophagy.

The Relationship Between the Level of Serum ESM-1 and Lp-PLA2 in Patients With Acute ST-Segment Elevation Myocardial Infarction

Acute ST‐segment elevation myocardial infarction (STEMI) is the most lethal coronary heart disease with vascular endothelium dysfunction and inflammation in the disease development process. Endothelial cell‐specific molecule 1 (ESM‐1) and lipoprotein‐associated phospholipase A2 (Lp‐PLA2) are important for the diagnosis and characterization of STEMI. To date, no studies have reported the correlation between ESM‐1 and Lp‐PLA2 levels in patients with STEMI, which may be an important predictor of the fatal disease. To measure the level of serum ESM‐1 and Lp‐PLA2, and to evaluate the relationship and the clinical significance of these two biomarkers in patients with acute STEMI, 37 inpatients with acute STEMI were sequentially enrolled in the research group and 24 study objects with normal coronary artery function were included in the control group. The measurement of the relative parameters was done by enzyme‐linked immunosorbent assay using blood samples taken from the median cubital vein while the inpatients were enrolled. The levels of serum SEM‐1 and Lp‐PLA2 were significantly higher in patients with acute STEMI than in study objects with normal coronary artery function (P < 0.05). A significant correlation of serum SEM‐1 and Lp‐PLA2 was observed, leading to close linearity (r² = 0.8131, P < 0.0001). In conclusion, the endothelium dysfunction factor ESM‐1 and inflammatory factor Lp‐PLA2 are significantly higher and correlated in patients with acute STEMI. These two factors could be novel and effective biomarkers for acute STEMI diagnosis and evaluation.

Myocardial ischaemia-reperfusion injury and cardioprotection in perspective

Despite the increasing use and success of interventional coronary reperfusion strategies, morbidity and mortality from acute myocardial infarction are still substantial. Myocardial infarct size is a major determinant of prognosis in these patients. Therefore, cardioprotective strategies aim to reduce infarct size. However, a perplexing gap exists between the many preclinical studies reporting infarct size reduction with mechanical and pharmacological interventions and the poor translation into better clinical outcomes in patients. This Review revisits the pathophysiology of myocardial ischaemia-reperfusion injury, including the role of autophagy and forms of cell death such as necrosis, apoptosis, necroptosis and pyroptosis. Other cellular compartments in addition to cardiomyocytes are addressed, notably the coronary microcirculation. Preclinical and clinical research developments in mechanical and pharmacological approaches to induce cardioprotection, and their signal transduction pathways, are discussed. Additive cardioprotective interventions are advocated. For clinical translation into treatments for patients with acute myocardial infarction, who typically are of advanced age, have comorbidities and are receiving several medications, not only infarct size reduction but also attenuation of coronary microvascular obstruction, as well as longer-term targets including infarct repair and reverse remodelling, must be considered to improve patient outcomes. Future clinical trials must focus on patients who really need adjunct cardioprotection, that is, those with severe haemodynamic alterations.

Microencapsulated Insulin-Like Growth Factor-1 therapy improves cardiac function and reduces fibrosis in a porcine acute myocardial infarction model

Insulin-like growth factor-1 (IGF-1) has demonstrated beneficial effects after myocardial infarction (MI). Microencapsulation of IGF-1 could potentially improve results. We aimed to test the effect of an intracoronary (IC) infusion of microencapsulated IGF-1 in a swine acute MI model. For that purpose IC injection of a 10 ml solution of 5 × 106 IGF-1 loaded microspheres (MSPs) (n = 8, IGF-1 MSPs), 5 × 106 unloaded MSPs (n = 9; MSPs) or saline (n = 7; CON) was performed 48 hours post-MI. Left ventricular ejection fraction (LVEF), indexed ventricular volumes and infarct size (IS) were determined by cardiac magnetic resonance at pre-injection and 10 weeks. Animals were euthanized at 10 weeks, and myocardial fibrosis and vascular density were analysed. End-study LVEF was significantly greater in IGF-1 MSPs compared to MSPs and CON, while ventricular volumes exhibited no significant differences between groups. IS decreased over time in all groups. Collagen volume fraction on the infarct area was significantly reduced in IGF-1 MSPs compared to CON and MSPs. Vascular density analysis of infarct and border zones showed no significant differences between groups. In conclusion, the IC injection of 5 × 106 IGF-1 loaded MSPs in a porcine acute MI model successfully improves cardiac function and limits myocardial fibrosis, which could be clinically relevant.

The inhibition of apoptosis through myocardial postconditioning by affecting Fas/FasIg signaling through miR139-3p and miR181a-1

BACKGROUND AND AIM OF THE STUDY

Ischemic postconditioning (PostC) is considered to be one of the strongest mechanisms limiting the extent of myocardial infarction, and reducing ischemia-reperfusion (I/R) injury. I/R-induced myocardial injury results in apoptosis, autophagy, and necrosis. The aim of the present study was to investigate the roles of the necrotic gene cytochrome b-245 beta chain (Cybb); Cybb-related microRNA miR139-3p; the autophagy gene Beclin-1 (Becn1); proapoptotic genes Fas, Faslg and growth arrest and DNA-damage-inducible 45 alpha (Gadd45a); and apoptosis-related microRNA miR181a-1 levels on I/R injury, as well as, the potential protective effects of PostC through this gene and microRNAs.

METHODS

The left main coronary artery was subjected to ischemia for 30 minutes, followed by reperfusion for 120 minutes. PostC involved three cycles of I/R, each lasting 10 seconds. Gene and microRNA levels were analyzed using a quantitative reverse transcription-polymerase chain reaction.

RESULTS

Although an increase was observed in the expression levels of the Cybb, Fas, Faslg and Gadd45a genes, the miR139-3p, miR181a-1, and Becn1 expression levels were found to decrease with I/R injury. PostC was determined to restore the expression of all the genes to the normal levels.

CONCLUSIONS

The abovementioned genes can be used as important prognostic markers in the diagnosis of reperfusion injury and in the evaluation of treatment efficacy. It was further noted that increased expression of CYBB, which is one of the target genes for miR139-3p, and a decreased expression of miR181a-1 may cause apoptosis by affecting Fas and Faslg signaling. PostC can inhibit apoptosis by increasing miR139-3p and miR181a-1 levels.

Egr-1 functions as a master switch regulator of remote ischemic preconditioning-induced cardioprotection

Despite improved treatment options myocardial infarction (MI) is still a leading cause of mortality and morbidity worldwide. Remote ischemic preconditioning (RIPC) is a mechanistic process that reduces myocardial infarction size and protects against ischemia reperfusion (I/R) injury. The zinc finger transcription factor early growth response-1 (Egr-1) is integral to the biological response to I/R, as its upregulation mediates the increased expression of inflammatory and prothrombotic processes. We aimed to determine the association and/or role of Egr-1 expression with the molecular mechanisms controlling the cardioprotective effects of RIPC. This study used H9C2 cells in vitro and a rat model of cardiac ischemia reperfusion (I/R) injury. We silenced Egr-1 with DNAzyme (ED5) in vitro and in vivo, before three cycles of RIPC consisting of alternating 5 min hypoxia and normoxia in cells or hind-limb ligation and release in the rat, followed by hypoxic challenge in vitro and I/R injury in vivo. Post-procedure, ED5 administration led to a significant increase in infarct size compared to controls (65.90 ± 2.38% vs. 41.00 ± 2.83%, p < 0.0001) following administration prior to RIPC in vivo, concurrent with decreased plasma IL-6 levels (118.30 ± 4.30 pg/ml vs. 130.50 ± 1.29 pg/ml, p < 0.05), downregulation of the cardioprotective JAK-STAT pathway, and elevated myocardial endothelial dysfunction. In vitro, ED5 administration abrogated IL-6 mRNA expression in H9C2 cells subjected to RIPC (0.95 ± 0.20 vs. 6.08 ± 1.40-fold relative to the control group, p < 0.05), resulting in increase in apoptosis (4.76 ± 0.70% vs. 2.23 ± 0.34%, p < 0.05) and loss of mitochondrial membrane potential (0.57 ± 0.11% vs. 1.0 ± 0.14%-fold relative to control, p < 0.05) in recipient cells receiving preconditioned media from the DNAzyme treated donor cells. This study suggests that Egr-1 functions as a master regulator of remote preconditioning inducing a protective effect against myocardial I/R injury through IL-6-dependent JAK-STAT signaling.

The Role of Heme Oxygenase-1 in Remote Ischemic and Anesthetic Organ Conditioning

The cytoprotective effects of the heme oxygenase (HO) pathway are widely acknowledged. These effects are mainly mediated by degradation of free, pro-oxidant heme and the generation of carbon monoxide (CO) and biliverdin. The underlying mechanisms of protection include anti-oxidant, anti-apoptotic, anti-inflammatory and vasodilatory properties. Upregulation of the inducible isoform HO-1 under stress conditions plays a crucial role in preventing or reducing cell damage. Therefore, modulation of the HO-1 system might provide an efficient strategy for organ protection. Pharmacological agents investigated in the context of organ conditioning include clinically used anesthetics and sedatives. A review from Hoetzel and Schmidt from 2010 nicely summarized the effects of anesthetics on HO-1 expression and their role in disease models. They concluded that HO-1 upregulation by anesthetics might prevent or at least reduce organ injury due to harmful stimuli. Due to its clinical safety, anesthetic conditioning might represent an attractive pharmacological tool for HO-1 modulation in patients. Remote ischemic conditioning (RIC), first described in 1993, represents a similar secure option to induce organ protection, especially in its non-invasive form. The efficacy of RIC has been intensively studied herein, including on patients. Studies on the role of RIC in influencing HO-1 expression to induce organ protection are emerging. In the first part of this review, recently published pre-clinical and clinical studies investigating the effects of anesthetics on HO-1 expression patterns, the underlying signaling pathways mediating modulation and its causative role in organ protection are summarized. The second part of this review sums up the effects of RIC.

VEGF-A plasma levels are associated with microvascular obstruction in patients with ST-segment elevation myocardial infarction

BACKGROUND

Microvascular obstruction (MVO) is associated with poor outcome after ST-segment elevation myocardial infarction (STEMI). Vascular endothelial growth factor-A (VEGF-A) is a vascular permeability inducer playing a key role in MVO pathogenesis. We aimed to assess whether VEGF-A levels are associated with MVO, when evaluated by magnetic resonance imaging (MRI) in STEMI patients.

METHODS

The multicenter prospective PREGICA study included a CMR substudy with all consecutive patients with a first STEMI who had undergone cardiac MRI at baseline and at 6-month follow-up. Patients with initial TIMI flow >1 were excluded. VEGF-A levels were measured in blood samples drawn at inclusion.

RESULTS

Between 2010 and 2017, 147 patients (mean age 57 ± 10 years; 84% males) were included. MVO was present in 65 (44%) patients. After multivariate analysis, higher troponin peak (OR 1.005; 95% CI 1.001-1.008; p = 0.007) and VEGF-A levels (OR 1.003; 95% CI 1.001-1.005; p = 0.015) were independently associated with MVO. When considering only patients with successful percutaneous coronary intervention (final TIMI flow 3, n = 130), higher troponin peak (p = 0.004) and VEGF-A levels (p = 0.03) remained independently predictive of MVO. Moreover, MVO was associated with adverse left ventricular (LV) remodeling and VEGF-A levels were significantly and inversely correlated with LV ejection fraction (EF) at 6-month follow-up.

CONCLUSION

Our results show that VEGF-A levels were independently associated with MVO during STEMI and correlated with mid-term LVEF alteration. VEGF-A could therefore be considered as a biomarker of MVO in STEMI patients and be used to stratify patient prognosis.

A Trial of Two Anesthetic Regimes for Minimally Invasive Mitral Valve Repair

OBJECTIVE

Minimally invasive mitral valve repair may be associated with prolonged cardioplegic arrest times and ischemic reperfusion injury. Intravenous (propofol) and volatile (sevoflurane) anesthesia are used routinely during cardiac surgery and are thought to provide cardioprotection; however, the individual contribution of each regimen to cardioprotection is unknown. Therefore, the authors sought to compare the cardioprotective effects of propofol and sevoflurane anesthesia in patients undergoing minimally invasive mitral valve repair.

DESIGN

A single-center single-blind randomized controlled trial.

SETTING

A specialized regional cardiac surgery center in Italy.

PARTICIPANTS

The study enrolled 62 adults undergoing elective isolated minimally invasive mitral valve repair for degenerative disease. Exclusion criteria included secondary mitral regurgitation, previously treated coronary artery disease, diabetes mellitus, chronic renal failure requiring dialysis, atrial fibrillation, and documented allergy to either propofol or sevoflurane.

INTERVENTIONS

All patients received video-assisted minimally invasive right minithoracotomy. Patients were randomized to receive propofol or sevoflurane anesthesia in a 1:1 ratio.

MEASUREMENTS AND MAIN RESULTS

Cardiac troponin I release was measured over the first 72 hours postoperatively. Operative, cross-clamp, and total bypass times were similar between groups. Cardiac troponin I release was reduced nonsignificantly in the propofol group (p = 0.62), and peak troponin I release was correlated with cross-clamp time in both groups. There were no differences in terms of intraoperative lactate release and blood pH between groups.

CONCLUSION

Propofol and sevoflurane anesthesia were associated with similar degrees of myocardial injury, indicating comparable cardioprotection. Myocardial injury was related directly to the duration of cardioplegic arrest.

Direct evidence that hypoxia triggers the cardioprotective response of ischemic preconditioning in a dog double-circuit cardiopulmonary bypass model

AIMS

It has been widely accepted that ischemic preconditioning (IPC) exhibits a promising and reproducible cardioprotective effect against ischemia/reperfusion (I/R) injury. However, the actual trigger that amplifies the molecular signaling and protects I/R heart is still unclear.

MAIN METHODS

To separate the factors involved in IPC, we established a dog double-circuit cardiopulmonary bypass (CPB) model, which consists of a systemic circuit and a coronary circuit. Forty-two male adult beagle dogs were randomly allocated into 7 groups: sham, I/R, IPC, hypoxia preconditioning (HPC), accumulated metabolite preconditioning (MPC), oxygenated or deoxygenated erythrocytes preconditioning (OxyEPC and DeoxyEPC). After pretreatment, dogs were subjected to 2 h-cardiac arrest and 2 h-reperfusion.

KEY FINDINGS

There were no differences in the cardiac function and hemodynamic parameters at baseline among groups. Like IPC, the hypoxia-related pretreatments HPC and DeoxyEPC improved post-arrest left ventricular systolic/diastolic performance and reduced pulmonary vascular resistance. The cardiac oxygen (O₂) utilization was also greatly elevated in these hypoxia-related pretreatment groups, as evidenced by increased cardiac O₂ consumption (VO₂) and O₂ extraction index (O₂EI) and suppressed lactate level. Besides, we did not observe improvement of these parameters in the MPC and OxyEPC groups. Further study indicated that these hypoxia-related pretreatments were associated with the attenuation of pro-inflammatory cytokines release and the elevation of complex I-supported mitochondrial respiration.

SIGNIFICANCE

With a dog double-circuit CPB model, we demonstrated that hypoxia is the actual trigger to initiate the cardioprotective effect of IPC in vivo, which was related to reduced cardiac inflammation and ameliorated complex-I supported mitochondrial function.

Relationship between CMR-derived parameters of ischemia/reperfusion injury and the timing of CMR after reperfused ST-segment elevation myocardial infarction

BACKGROUND

To investigate the influence of cardiovascular magnetic resonance (CMR) timing after reperfusion on CMR-derived parameters of ischemia/reperfusion (I/R) injury in patients with ST-segment elevation myocardial infarction (STEMI).

METHODS

The study included 163 reperfused STEMI patients undergoing CMR during the index hospitalization. Patients were divided according to the time between revascularization and CMR (Trevasc-CMR: Tertile-1 ≤ 43; 43 < Tertile-2 ≤ 93; Tertile-3 > 93 h). T2-mapping derived area-at-risk (AAR) and intramyocardial-hemorrhage (IMH), and late gadolinium enhancement (LGE)-derived infarct size (IS) and microvascular obstruction (MVO) were quantified. T1-mapping was performed before and > 15 min after Gd-based contrast-agent administration yielding extracellular volume (ECV) of infarct.

RESULTS

Main factors influencing I/R injury were homogenously balanced across Trevasc-CMR tertiles. T2 values of infarct and remote regions increased with increasing Trevasc-CMR tertiles (infarct: 60.0 ± 4.9 vs 63.5 ± 5.6 vs 64.8 ± 7.5 ms; P < 0.001; remote: 44.3 ± 2.8 vs 46.1 ± 2.8 vs ± 46.1 ± 3.0; P = 0.001). However, T2 value of infarct largely and significantly exceeded that of remote myocardium in each tertile yielding comparable T2-mapping-derived AAR extent throughout Trevasc-CMR tertiles (17 ± 9% vs 19 ± 9% vs 18 ± 8% of LV, respectively, P = 0.385). Similarly, T2-mapping-based IMH detection and quantification were independent of Trevasc-CMR. LGE-derived IS and MVO were not influenced by Trevasc-CMR (IS: 12 ± 9% vs 12 ± 9% vs 14 ± 9% of LV, respectively, P = 0.646). In 68 patients without MVO, T1-mapping based ECV of infarct region was comparable across Trevasc-CMR tertiles (P = 0.470).

CONCLUSION

In STEMI patients, T2 values of infarct and remote myocardium increase with increasing CMR time after revascularization. However, these changes do not give rise to substantial variation of T2-mapping-derived AAR size nor of other CMR-based parameters of I/R.

TRIAL REGISTRATION

ISRCTN03522116 . Registered 30.4.2018 (retrospectively registered).

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.

The pathophysiology of acute myocardial infarction and strategies of protection beyond reperfusion: a continual challenge

The incidence of ST segment elevation myocardial infarction (STEMI) has decreased over the last two decades in developed countries, but mortality from STEMI despite widespread access to reperfusion therapy is still substantial as is the development of heart failure, particularly among an expanding older population. In developing countries, the incidence of STEMI is increasing and interventional reperfusion is often not available. We here review the pathophysiology of acute myocardial infarction and reperfusion, notably the temporal and spatial evolution of ischaemic and reperfusion injury, the different modes of cell death, and the resulting coronary microvascular dysfunction. We then go on to briefly characterize the cardioprotective phenomena of ischaemic preconditioning, ischaemic postconditioning, and remote ischaemic conditioning and their underlying signal transduction pathways. We discuss in detail the attempts to translate conditioning strategies and drug therapy into the clinical setting. Most attempts have failed so far to reduce infarct size and improve clinical outcomes in STEMI patients, and we discuss potential reasons for such failure. Currently, it appears that remote ischaemic conditioning and a few drugs (atrial natriuretic peptide, exenatide, metoprolol, and esmolol) reduce infarct size, but studies with clinical outcome as primary endpoint are still underway.

Coronary microembolization and microvascular dysfunction

Plaque erosion, fissuring or rupture occurs spontaneously or during coronary interventions. At some residual blood flow, the atherothrombotic debris is washed into the coronary microcirculation, causing physical obstruction, vasoconstriction, inflammation and ultimately microinfarction. Coronary microembolization also contributes to microvascular obstruction in reperfused acute myocardial infarction. Patients with microvascular obstruction after reperfused myocardial infarction have worse prognosis. Cardioprotective strategies to avoid acute coronary microembolization and rescue myocardium from microvascular obstruction have not yet been established in clinical practice. Subclinical coronary microembolization together with release of thrombogenic, vasoconstrictor and inflammatory substances from a culprit lesion can sensitize the coronary microcirculation and contribute to angina in the absence of major epicardial coronary obstruction. Repetitive coronary microembolization can induce progressive loss of functional cardiomyocytes and induce heart failure in the absence of overt myocardial infarction.

Acute and long-term cardioprotective effects of the Traditional Chinese Medicine MLC901 against myocardial ischemia-reperfusion injury in mice

MLC901, a traditional Chinese medicine containing a cocktail of active molecules, both reduces cerebral infarction and improves recovery in patients with ischemic stroke. The aim of this study was to evaluate the acute and long-term benefits of MLC901 in ischemic and reperfused mouse hearts. Ex vivo, under physiological conditions, MLC901 did not show any modification in heart rate and contraction amplitude. However, upon an ischemic insult, MLC901 administration during reperfusion, improved coronary flow in perfused hearts. In vivo, MLC901 (4 µg/kg) intravenous injection 5 minutes before reperfusion provided a decrease in both infarct size (49.8%) and apoptosis (49.9%) after 1 hour of reperfusion. Akt and ERK1/2 survival pathways were significantly activated in the myocardium of those mice. In the 4-month clinical follow-up upon an additional continuous per os administration, MLC901 treatment decreased cardiac injury as revealed by a 45%-decrease in cTnI plasmatic concentrations and an improved cardiac performance assessed by echocardiography. A histological analysis revealed a 64%-decreased residual scar fibrosis and a 44%-increased vascular density in the infarct region. This paper demonstrates that MLC901 treatment was able to provide acute and long-term cardioprotective effects in a murine model of myocardial ischemia-reperfusion injury in vivo.

Mode of perfusion influences infarct size, coronary flow and stress kinases in the isolated mouse heart

AIM

The isolated, retrogradely perfused heart (modified Langendorff model) is a widely used method in experimental heart research. The presence of an intraventricular balloon is necessary to get functional measurements. We have previously shown that the balloon induces phosphorylation of some suggested cardioprotective mitogen-activated protein kinases (MAPK): P38-MAPK, ERK 1/2 and JNK. We hypothesized that the balloon could influence cardioprotection, protect against ischaemia reperfusion injury and interfere with coronary flow.

METHODS AND RESULTS

Isolated mouse hearts were perfused for 5, 10, 20, 40 and 60 min with a balloon in the left ventricle. We found a wavelike phosphorylation of all MAPK while AKT displayed a gradual dephosphorylation when compared to non-perfused hearts. Hearts were subjected to 20 min of stabilization with or without the balloon, followed by 35 min of ischaemia and 120 min of reperfusion. Although the MAPK were phosphorylated, the infarcts were larger in the balloon group. When the balloon was present during the entire protocol, compared to removal at the end of ischaemia, the infarct size was also larger, especially in the endocardial layer. The balloon reduced post-ischaemic endocardial coronary flow, despite a higher average flow, indicating a hyperperfused epicard. Blocking the balloon-induced ERK 1/2 phosphorylation during stabilization did not affect infarct size. The effect of post-conditioning was influenced by the balloon, showing reduced infarct size when the balloon was present.

CONCLUSION

The balloon used for pressure measurements may contributes to cell death possibly by reducing endocardial coronary flow.

The Coronary Circulation as a Target of Cardioprotection

The atherosclerotic coronary vasculature is not only the culprit but also a victim of myocardial ischemia/reperfusion injury. Manifestations of such injury are increased vascular permeability and edema, endothelial dysfunction and impaired vasomotion, microembolization of atherothrombotic debris, stasis with intravascular cell aggregates, and finally, in its most severe form, capillary destruction with hemorrhage. In animal experiments, local and remote ischemic pre- and postconditioning not only reduce infarct size but also these manifestations of coronary vascular injury, as do drugs which recruit signal transduction steps of conditioning. Clinically, no-reflow is frequently seen after interventional reperfusion, and it carries an adverse prognosis. The translation of cardioprotective interventions to clinical practice has been difficult to date. Only 4 drugs (brain natriuretic peptide, exenatide, metoprolol, and esmolol) stand unchallenged to date in reducing infarct size in patients with reperfused acute myocardial infarction; unfortunately, for these drugs, no information on their impact on the ischemic/reperfused coronary circulation is available.

Feasibility of Extracorporeal Shock Wave Myocardial Revascularization Therapy for Post-Acute Myocardial Infarction Patients and Refractory Angina Pectoris Patients

Extracorporeal shockwave myocardial revascularization (ESMR) is one of the new treatment options for refractory angina pectoris (RAP), and some studies have indicated its effectiveness. A single-arm prospective trial to assess the feasibility of ESMR using Cardiospec for patients with post-acute myocardial infarction (AMI) and RAP was designed and performed. The patients were treated with 9 sessions of ESMR to the ischemic areas for 9 weeks. The feasibility measures included echocardiography; cardiac magnetic resonance imaging; troponin T, creatine kinase-MB (CK-MB), and brain natriuretic peptide testing; and a Seattle Angina Questionnaire (SAQ) survey. Three post-AMI patients and 3 RAP patients were enrolled. The post-AMI patients had already undergone revascularization with percutaneous coronary intervention (PCI) in the acute phase. In two patients, adverse events requiring admission occurred: one a lumbar disc hernia in a post-AMI patient and the other congestive heart failure resulting in death in an RAP patient. No apparent elevations in CK-MB and troponin T levels during the trial were observed. Echocardiography revealed no remarkable changes of ejection fraction; however, septal E/E' tended to decrease after treatments (11.6 ± 4.8 versus 9.2 ± 2.8, P = 0.08). Concerning the available SAQ scores for two RAP patients, one patient reported improvements in angina frequency and treatment satisfaction and the other reported improvements in physical limitations and angina stability. In this feasibility study, ESMR seems to be a safe treatment for both post-AMI patients and RAP patients. The efficacy of ESMR for post-AMI patients remains to be evaluated with additional studies.

Effect of remote ischemic conditioning on infarct size in patients with anterior ST-elevation myocardial infarction

BACKGROUND

Previous studies indicate that remote ischemic conditioning performed before percutaneous coronary intervention (PCI) reduces infarct size in patients with ST-elevation myocardial infarction (STEMI). It remains unclear whether remote conditioning affords protection when performed in adjunct to primary PCI. We aimed to study whether remote ischemic per-postconditioning (RIperpostC) initiated after admission to the catheterization laboratory attenuates myocardial infarct size in patients with anterior STEMI.

METHODS

In this prospective multicenter trial 93 patients with anterior STEMI were randomized to RIperpostC or sham procedure as adjunct to primary PCI. RIperpostC was started on arrival in the catheterization laboratory by 5-minute cycles of inflation and deflation of a blood pressure cuff around the left thigh and continued throughout the PCI procedure. Infarct size and myocardium at risk were determined by cardiac magnetic resonance at day 4 to 7. The primary outcome was myocardial salvage index.

RESULTS

There was no significant difference in myocardial salvage index between the RIperpostC and control group (median 48.5% and interquartile range 30.9%-60.8% vs 49.2% [42.1%-58.8%]). Neither did absolute infarct size in relation to left ventricular myocardial volume differ significantly (RIperpostC 20.6% [14.1%-31.7%] vs control 17.9% [13.4%-25.0%]). The RIperpostC group had larger myocardial area at risk than the control group (43.1% (35.4%-49.7%) vs 37.0% (30.8%-44.1%) of the left ventricle, P=.03). Peak value and area under the curve for troponin T did not differ significantly between the study groups.

CONCLUSIONS

RIperpostC initiated after admission to the catheterization laboratory in patients with anterior STEMI did not confer protection against reperfusion injury.

9th Hatter Biannual Meeting: position document on ischaemia/reperfusion injury, conditioning and the ten commandments of cardioprotection

In the 30 years since the original description of ischaemic preconditioning, understanding of the pathophysiology of ischaemia/reperfusion injury and concepts of cardioprotection have been revolutionised. In the same period of time, management of patients with coronary artery disease has also been transformed: coronary artery and valve surgery are now deemed routine with generally excellent outcomes, and the management of acute coronary syndromes has seen decade on decade reductions in cardiovascular mortality. Nonetheless, despite these improvements, cardiovascular disease and ischaemic heart disease in particular, remain the leading cause of death and a significant cause of long-term morbidity (with a concomitant increase in the incidence of heart failure) worldwide. The need for effective cardioprotective strategies has never been so pressing. However, despite unequivocal evidence of the existence of ischaemia/reperfusion in animal models providing a robust rationale for study in man, recent phase 3 clinical trials studying a variety of cardioprotective strategies in cardiac surgery and acute ST-elevation myocardial infarction have provided mixed results. The investigators meeting at the Hatter Cardiovascular Institute workshop describe the challenge of translating strong pre-clinical data into effective clinical intervention strategies in patients in whom effective medical therapy is already altering the pathophysiology of ischaemia/reperfusion injury-and lay out a clearly defined framework for future basic and clinical research to improve the chances of successful translation of strong pre-clinical interventions in man.

Treatment of Myocardial Ischemia/Reperfusion Injury by Ischemic and Pharmacological Postconditioning

Timely reperfusion is the only way to salvage ischemic myocardium from impending infarction. However, reperfusion also adds a further component to myocardial injury such that the ultimate infarct size is the result of both ischemia- and reperfusion-induced injury. Modification of reperfusion can attenuate reperfusion injury and thus reduce infarct size. Ischemic postconditioning is a maneuver of repeated brief interruption of reperfusion by short-lasting coronary occlusions which results in reduced infarct size. Cardioprotection by ischemic postconditioning is mediated through delayed reversal of acidosis and the activation of a complex signal transduction cascade, including triggers such as adenosine, bradykinin, and opioids, mediators such as protein kinases and, notably, mitochondrial function as effector. Inhibition of the mitochondrial permeability transition pore appears to be a final signaling step of ischemic postconditioning. Several drugs which recruit in part such signaling steps of ischemic postconditioning can induce cardioprotection, even when the drug is only administered at reperfusion, that is, there is also pharmacological postconditioning. Ischemic and pharmacological postconditioning have been translated to patients with acute myocardial infarction in proof-of-concept studies, but further mechanistic insight is needed to optimize the conditions and algorithms of cardioprotection by postconditioning.

Interaction of risk factors, comorbidities, and comedications with ischemia/reperfusion injury and cardioprotection by preconditioning, postconditioning, and remote conditioning

Pre-, post-, and remote conditioning of the myocardium are well described adaptive responses that markedly enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and provide therapeutic paradigms for cardioprotection. Nevertheless, more than 25 years after the discovery of ischemic preconditioning, we still do not have established cardioprotective drugs on the market. Most experimental studies on cardioprotection are still undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of cardiovascular risk factors. However, ischemic heart disease in humans is a complex disorder caused by, or associated with, cardiovascular risk factors and comorbidities, including hypertension, hyperlipidemia, diabetes, insulin resistance, heart failure, altered coronary circulation, and aging. These risk factors induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Moreover, some of the medications used to treat these risk factors, including statins, nitrates, and antidiabetic drugs, may impact cardioprotection by modifying cellular signaling. The aim of this article is to review the recent evidence that cardiovascular risk factors and their medication may modify the response to cardioprotective interventions. We emphasize the critical need to take into account the presence of cardiovascular risk factors and 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 risk factors.

Association Between Preinfarction Angina and Angiographic Findings in Non-ST-Segment Elevation Myocardial Infarction

BACKGROUND

The association between preinfarction angina and angiographic findings has not been elucidated in patients with non-ST-segment elevation myocardial infarction (NSTEMI).

HYPOTHESIS

Patients with preinfarction angina have favorable angiographic findings.

METHODS

This retrospective study analyzed 481 patients who underwent coronary angiography within 5 days of presenting NSTEMI. Preinfarction angina was defined as experiencing ≥1 chest-pain episode within 7 days prior to admission. Infarct size was measured as the peak cardiac troponin I (cTnI) level, and large myocardial infarction (MI) was defined as a peak cTnI level >85th percentile value in the study population. Infarct-related artery (IRA) patency was defined as Thrombolysis In Myocardial Infarction grade 2 or 3 flow. Clinical and angiographic characteristics and in-hospital mortality were compared between patients with and without preinfarction angina.

RESULTS

Among 481 patients, 200 (42%) had preinfarction angina. Preinfarction angina was associated with smaller infarct size, indicated by lower peak cTnI levels (P = 0.006) and lower incidence of large MI (P = 0.02), and IRA patency (P = 0.03). There was no significant difference in in-hospital mortality. On multivariate analysis, both preinfarction angina (odds ratio: 0.53, 95% confidence interval: 0.29-0.94, P = 0.03) and IRA patency (odds ratio: 0.30, 95% confidence interval: 0.17-0.52, P < 0.001) were independent negative predictors of large MI.

CONCLUSION

Our study demonstrates that preinfarction angina is a predictor of smaller infarct size and infarct-related artery patency in NSTEMI patients, suggesting that NSTEMI patients presenting without preinfarction angina are at increased risk of developing a large MI.

Molecular basis of cardioprotection: signal transduction in ischemic pre-, post-, and remote conditioning

Reperfusion is mandatory to salvage ischemic myocardium from infarction, but reperfusion per se contributes to injury and ultimate infarct size. Therefore, cardioprotection beyond that by timely reperfusion is needed to reduce infarct size and improve the prognosis of patients with acute myocardial infarction. The conditioning phenomena provide such cardioprotection, insofar as brief episodes of coronary occlusion/reperfusion preceding (ischemic preconditioning) or following (ischemic postconditioning) sustained myocardial ischemia with reperfusion reduce infarct size. Even ischemia/reperfusion in organs remote from the heart provides cardioprotection (remote ischemic conditioning). The present review characterizes the signal transduction underlying the conditioning phenomena, including their physical and chemical triggers, intracellular signal transduction, and effector mechanisms, notably in the mitochondria. Cardioprotective signal transduction appears as a highly concerted spatiotemporal program. Although the translation of ischemic postconditioning and remote ischemic conditioning protocols to patients with acute myocardial infarction has been fairly successful, the pharmacological recruitment of cardioprotective signaling has been largely disappointing to date.

Lack of Benefit of Ischemic Postconditioning After Routine Thrombus Aspiration During Reperfusion

Objectives:

The underutilization of manual thrombus aspiration (MTA) may have reduced the benefits of ischemic postconditioning (PostCon), as it reduces thrombus embolization. We aimed to assess the benefits of PostCon in patients with ST-segment elevation myocardial infarction (STEMI) after the systematic utilization of MTA.

Methods:

A total of 87 patients were enrolled in a prospective, randomized trial (43 PostCon and 44 controls). After MTA, PostCon was performed on the treatment group by applying 4 cycles of alternate reperfusion and reocclusion (60 seconds each) using the angioplasty balloon. The primary end point was infarct size assessed by the area under the curve (AUC) of troponin T (TnT) activity. The secondary end points were left ventricle ejection fraction (LVEF) and major cardiac events (new myocardial infarction or cardiac death) both at discharge and at follow-up.

Results:

The AUC for TnT was no different with respect to study arms (median [interquartile range]): PostCon = 8.9 (10.6) versus control = 8.2 (10.6), P = .68. Left ventricle ejection fraction improved from in-hospital to follow-up (9 ± 3 months) for the entire cohort (46.3% ± 7.3% vs 52.2% ± 10.7%, P < .001), with no differences between PostCon and controls (51.6% ± 9.5% vs 52.7% ± 11.9%, P = .89); major cardiac events at 14 ± 4 months of follow-up were also no different (PostCon = 1.0 (2.3%) vs control = 0, P = .49).

Conclusion:

In patients with STEMI treated with MTA, PostCon offered no benefits to infarct size, LVEF, or major cardiac events.

Plasma from human volunteers subjected to remote ischemic preconditioning protects human endothelial cells from hypoxia-induced cell damage

Short repeated cycles of peripheral ischemia/reperfusion (I/R) can protect distant organs from subsequent prolonged I/R injury; a phenomenon known as remote ischemic preconditioning (RIPC). A RIPC-mediated release of humoral factors might play a key role in this protection and vascular endothelial cells are potential targets for these secreted factors. In the present study, RIPC-plasma obtained from healthy male volunteers was tested for its ability to protect human umbilical endothelial cells (HUVEC) from hypoxia–induced cell damage. 10 healthy male volunteers were subjected to a RIPC-protocol consisting of 4 × 5 min inflation/deflation of a blood pressure cuff located at the upper arm. Plasma was collected before (T0; control), directly after (T1) and 1 h after (T2) the RIPC procedure. HUVEC were subjected to 24 h hypoxia damage and simultaneously incubated with 5 % of the respective RIPC-plasma. Cell damage was evaluated by lactate dehydrogenase (LDH)-measurements. Western blot experiments of hypoxia inducible factor 1 alpha (HIF1alpha), phosphorylated signal transducer and activator of transcription 5 (STAT5), protein kinase B (AKT) and extracellular signal-related kinase 1/2 (ERK-1/2) were performed. Furthermore, the concentrations of hVEGF were evaluated in the RIPC-plasma by sandwich ELISA. Hypoxia–induced cell damage was significantly reduced by plasma T1 (p = 0.02 vs T0). The protective effect of plasma T1 was accompanied by an augmentation of the intracellular HIF1alpha (p = 0.01 vs T0) and increased phosphorylation of ERK-1/2 (p = 0.03 vs T0). Phosphorylation of AKT and STAT5 remained unchanged. Analysis of the protective RIPC-plasma T1 showed significantly reduced levels of hVEGF (p = 0.01 vs T0). RIPC plasma protects endothelial cells from hypoxia–induced cell damage and humoral mediators as well as intracellular HIF1alpha may be involved.

Extracellular signalling molecules in the ischaemic/reperfused heart - druggable and translatable for cardioprotection?

In patients with acute myocardial infarction, timely reperfusion is essential to limit infarct size. However, reperfusion also adds to myocardial injury. Brief episodes of ischaemia/reperfusion in the myocardium or on organ remote from the heart, before or shortly after sustained myocardial ischaemia effectively reduce infarct size, provided there is eventual reperfusion. Such conditioning phenomena have been established in many experimental studies and also translated to humans. The underlying signal transduction, that is the molecular identity of triggers, mediators and effectors, is not clear yet in detail, but several extracellular signalling molecules, such as adenosine, bradykinin and opioids, have been identified to contribute to cardioprotection by conditioning manoeuvres. Several trials have attempted the translation of cardioprotection by such autacoids into a clinical scenario of myocardial ischaemia and reperfusion. Adenosine and its selective agonists reduced infarct size in a few studies, but this benefit was not translated into improved clinical outcome. All studies with bradykinin or drugs which increase bradykinin's bioavailability reported reduced infarct size and some of them also improved clinical outcome. Synthetic opioid agonists did not result in a robust infarct size reduction, but this failure of translation may relate to the cardioprotective properties of the underlying anaesthesia per se or of the comparator drugs. The translation of findings in healthy, young animals with acute coronary occlusion/reperfusion to patients of older age, with a variety of co-morbidities and co-medications, suffering from different scenarios of myocardial ischaemia/reperfusion remains a challenge.

2014 Williams Harvey Lecture: importance of coronary vasomotion abnormalities-from bench to bedside

Coronary vasomotion abnormalities play important roles in the pathogenesis of ischaemic heart disease, in which endothelial dysfunction and coronary artery spasm are substantially involved. Endothelial vasodilator functions are heterogeneous depending on the vessel size, with relatively greater role of nitric oxide (NO) in conduit arteries and predominant role of endothelium-derived hyperpolarizing factor (EDHF) in resistance arteries, where endothelium-derived hydrogen peroxide serves as an important EDHF. The functions of NO synthases in the endothelium are also heterogeneous with multiple mechanisms involved, accounting for the diverse functions of the endothelium in vasomotor as well as metabolic modulations. Cardiovascular abnormalities and metabolic phenotypes become evident when all three NO synthases are deleted, suggesting the importance of both NO and EDHF. Coronary artery spasm plays important roles in the pathogenesis of a wide range of ischaemic heart disease. The central mechanism of the spasm is hypercontraction of vascular smooth muscle cells (VSMCs), but not endothelial dysfunction, where activation of Rho-kinase, a molecular switch of VSMC contraction, plays a major role through inhibition of myosin light-chain phosphatase. The Rho-kinase pathway is also involved in the pathogenesis of a wide range of cardiovascular diseases and new Rho-kinase inhibitors are under development for various indications. The registry study by the Japanese Coronary Spasm Association has demonstrated many important aspects of vasospastic angina. The ongoing international registry study of vasospastic angina in six nations should elucidate the unknown aspects of the disorder. Coronary vasomotion abnormalities appear to be an important therapeutic target in cardiovascular medicine.

Myocardial conditioning: opportunities for clinical translation

Myocardial conditioning is an endogenous cardioprotective phenomenon that profoundly limits infarct size in experimental models. The current challenge is to translate this paradigm from the laboratory to the clinic. Accordingly, our goal in this review is to provide a critical summary of the progress toward, opportunities for, and caveats to, the successful clinical translation of postconditioning and remote conditioning, the 2 conditioning strategies considered to have the broadest applicability for real-world patient care. In the majority of phase II studies published to date, postconditioning evoked a ≈35% reduction of infarct size in ST-segment-elevation myocardial infarction patients. Essential criteria for the successful implementation of postconditioning include the appropriate choice of patients (ie, those with large risk regions and negligible collateral flow), timely application of the postconditioning stimulus (immediately on reperfusion), together with proper choice of end points (infarct size, with concomitant assessment of risk region). Remote conditioning has been applied in planned ischemic events (including cardiac surgery and elective percutaneous coronary intervention) and in ST-segment-elevation myocardial infarction patients during hospital transport. Controversies with regard to efficacy have emerged, particularly among surgical trials. These disparate outcomes in all likelihood reflect the remarkable heterogeneity within and among studies, together with a deficit in our understanding of the impact of these variations on the infarct-sparing effect of remote conditioning. Ongoing phase III trials will provide critical insight into the future role of postconditioning and remote conditioning as clinically relevant cardioprotective strategies.

The impact of the coronary collateral circulation on outcomes in patients with acute coronary syndromes: results from the ACUITY trial

OBJECTIVE

We sought to assess the prognostic role of collaterals in a large population of patients presenting with an acute coronary syndrome (ACS).

METHODS

The coronary collateral circulation was assessed by an independent angiographic core laboratory using the Rentrop Score in patients enrolled in the randomised Acute Catheterization and Urgent Intervention Triage Strategy trial.

RESULTS

The cohort comprised 5412 patients with moderate to high risk ACS. A total of 858 patients (16.0%) had visible collaterals while 4554 patients (84.0%) had no collaterals. After multivariable adjustment, there were no differences in clinical outcomes at 1 year between the groups, including major adverse cardiac events (MACE) (HR 0.94 (95% CI 0.76 to 1.16), p=0.55), mortality (HR 1.03 (0.65 to 1.62), p=0.91), myocardial infarction (MI) (HR 1.07 (0.83 to 1.38), p=0.60) and unplanned target vessel revascularisation (TVR) (HR 0.95 (0.71 to 1.28), p=0.75). Similarly, in the subgroup of patients undergoing percutaneous coronary intervention (PCI), the adjusted HR for major adverse cardiac events was 1.1 (0.76 to 1.61), p=0.595; 0.81 (0.10 to 6.44), p=0.999 for mortality; and 0.86 (0.54 to 1.35), p=0.564 for MI. The risk of unplanned TVR was increased (HR 2.74 (1.48 to 5.10), p=0.004).

CONCLUSIONS

In contrast to other studies, this large core laboratory-based analysis does not confirm a beneficial role of visible coronary collateral vessels on clinical outcomes in patients with ACS; the presence of collaterals was even associated with increased mortality in the unadjusted analysis. Collaterals were associated with a higher risk of TVR in patients undergoing PCI, a finding that may not have been fully corrected given confounders and clinical differences between the groups.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00093158.