'Conditioning' the heart during surgery

New Perspectives on Sex Steroid and Mineralocorticoid Receptor Signaling in Cardiac Ischemic Injury

The global burden of ischemic heart disease is burgeoning for both men and women. Although advances have been made, the need for new sex-specific therapies targeting key differences in cardiovascular disease outcomes in men and women remains. Mineralocorticoid receptor directed treatments have been successfully used for blood pressure control and heart failure management and represent a potentially valuable therapeutic option for ischemic cardiac events. Clinical and experimental data indicate that mineralocorticoid excess or inappropriate mineralocorticoid receptor (MR) activation exacerbates ischemic damage, and many of the intracellular response pathways activated in ischemia and subsequent reperfusion are regulated by MR. In experimental contexts, where MR are abrogated genetically or mineralocorticoid signaling is suppressed pharmacologically, ischemic injury is alleviated, and reperfusion recovery is enhanced. In the chronic setting, mineralocorticoid signaling induces fibrosis, oxidative stress, and inflammation, which can predispose to ischemic events and exacerbate post-myocardial infarct pathologies. Whilst a range of cardiac cell types are involved in mineralocorticoid-mediated regulation of cardiac function, cardiomyocyte-specific MR signaling pathways are key. Selective inhibition of cardiomyocyte MR signaling improves electromechanical resilience during ischemia and enhances contractile recovery in reperfusion. Emerging evidence suggests that the MR also contribute to sex-specific aspects of ischemic vulnerability. Indeed, MR interactions with sex steroid receptors may differentially regulate myocardial nitric oxide bioavailability in males and females, potentially determining sex-specific post-ischemic outcomes. There is hence considerable impetus for exploration of MR directed, cell specific therapies for both women and men in order to improve ischemic heart disease outcomes.

Time-of-Day and Clinical Outcomes After Surgical or Transcatheter Aortic Valve Replacement: Insights From the PARTNER Trials

BACKGROUND

Circadian rhythms may influence myocardial tolerance to ischemia-reperfusion phenomena occurring during cardiac procedures. While conflicting results exist on the effect of time-of-day on surgical aortic valve replacement (SAVR), afternoon procedures could be associated with a reduced risk of death, rehospitalization or periprocedural myocardial infarction, compared with morning procedures. We examined the impact of procedure time-of-day on outcomes after transcatheter aortic valve replacement (TAVR) or SAVR.

METHODS

We analyzed patients at intermediate- or high-surgical risk who underwent elective TAVR (n=4457) or SAVR (n=1129) in the PARTNER (Placement of Aortic Transcatheter Valve) 1 and 2 trials and registries according to time-of-day (morning versus afternoon) using the Kaplan-Meier event rates and multivariable Cox proportional hazards regression models. Sensitivity analysis was conducted using 1:1 propensity-score matching. The primary end point was all-cause death or rehospitalization at 2 years.

RESULTS

At 2 years, no difference was observed between patients operated in the morning versus the afternoon within the SAVR (32.3% versus 30.6%, adjusted hazard ratio, 1.08 [95% CI, 0.82-1.41], P=0.58) and TAVR cohorts (35.7% versus 35.4%, adjusted hazard ratio, 1.01 [95% CI, 0.89-1.14], P=0.86) with regards to the primary end point. Rates of periprocedural myocardial infarction were low and similar between morning and afternoon in SAVR (1.6% versus 1.0%, P=0.51) and TAVR (0.4% versus 0.4%, P=0.86), as were all other clinical end points. Similar results were observed in propensity-score matched analysis.

CONCLUSIONS

Procedure time-of-day was not associated with clinical outcomes after TAVR or SAVR. Registration: URL: https://www.clinicaltrials.gov; Unique identifiers: NCT00530894, NCT01314313, NCT03222141, and NCT03222128.

Myocardial remote ischemic preconditioning: from cell biology to clinical application

Remote ischemic preconditioning (rIPC) is a cardioprotective phenomenon where brief periods of ischemia followed by reperfusion of one organ/tissue can confer subsequent protection against ischemia/reperfusion injury in other organs, such as the heart. It involves activation of humoral, neural or systemic communication pathways inducing different intracellular signals in the heart. The main purpose of this review is to summarize the possible mechanisms involved in the rIPC cardioprotection, and to describe recent clinical trials to establish the efficacy of these strategies in cardioprotection from lethal ischemia/reperfusion injury. In this sense, certain factors weaken the subcellular mechanisms of rIPC in patients, such as age, comorbidities, medication, and anesthetic protocol, which could explain the heterogeneity of results in some clinical trials. For these reasons, further studies, carefully designed, are necessary to develop a clearer understanding of the pathways and mechanism of early and late rIPC. An understanding of the pathways is important for translation to patients.

An investigation of the effectiveness of oral cyclosporine on perioperative myocardial injury (PMI) in patients who undergo the surgical procedure of coronary artery bypass graft (CABG): A Randomized Controlled Clinical Trial

Background:

Routine clinical strategies for the prevention of myocardial infarction (MI) during the surgical procedure of CABG include cross-clamp fibrillation and cardioplegia have failed to decrease the risk of perioperative myocardial injury (PMI). Cyclosporine-A (CsA) might be able to prevent mitochondrial dysfunction and PMI.

Methods:

In the present clinical trial, patients were divided into two groups (Case receive 2.5 mg/kg CsA and Control receive a placebo) randomly. Moreover, patients were controlled by placebo through a double-blind, single-center trial 4-12 h before anesthesia. Perioperative blood tests include bilirubin, complete blood count, the amount of hemoglobin in whole blood, liver transaminases, and glomerular filtration rate (GFR). Blood samples were taken before surgery and at 24, 48, and 72 h after surgery and serum Troponin-I and CK-MB levels were determined in all blood samples using ELISA.

Results:

There were no significant differences between the two groups in the results of routine pre-operative blood results, intraoperative variables, and baseline characteristics (P > 0.05). There are significant correlations between cross clamp time and cTnI and CKMB levels in patients taking CsA. In patients with both diabetes and hypertension, postsurgical cTnI and CKMB levels decrease significantly in CsA compared to placebo group on 24, 48, and 72 h (P < 0.05). Moreover, patients with old MI, both postsurgical cTnI and CKMB levels decrease significantly in CsA compared to placebo group on 24 h and 48 h (P < 0.05).

Conclusions:

In patients with a long cross-clamping period, using an oral CSA single dose before conducting CABG surgery, the risk of PMI could be decreased. Also, oral CsA has protective effect for CABG in diabetic patients with hypertension.

Investigation of the underlying hub genes and mechanisms of reperfusion injury in patients undergoing coronary artery bypass graft surgery by integrated bioinformatic analyses

Background

Although coronary artery bypass graft (CABG) surgery is the main method to revascularize the occluded coronary vessels in coronary artery diseases, the full benefits of the operation are mitigated by ischemia-reperfusion (IR) injury. Although many studies have been devoted to reducing IR injury in animal models, the translation of this research into the clinical field has been disappointing. Our study aimed to explore the underlying hub genes and mechanisms of IR injury.

Methods

A weighted gene co-expression network analysis (WGCNA) was executed based on the expression profiles in patients undergoing CABG surgery (GSE29396). Functional annotation and protein-protein interaction (PPI) network construction were executed within the modules of interest. Potential hub genes were predicted, combining both intramodular connectivity (IC) and degrees. Meanwhile, potential transcription factors (TFs) and microRNAs (miRNAs) were predicted by corresponding bioinformatics tools.

Results

A total of 336 differentially expressed genes (DEGs) were identified. DEGs were mainly enriched in neutrophil activity and immune response. Within the modules of interest, 5 upregulated hub genes (IL-6, CXCL8, IL-1β, MYC, PTGS-2) and 6 downregulated hub genes (C3, TIMP1, VSIG4, SERPING1, CD163, and HP) were predicted. Predicted miRNAs (hsa-miR-333-5p, hsa-miR-26b-5p, hsa-miR-124-3p, hsa-miR-16-5p, hsa-miR-98-5p, hsa-miR-17-5p, hsa-miR-93-5p) and TF (STAT1) might have regulated gene expression in the most positively related module, while hsa-miR-333-5p and HSF-1 were predicted to regulate the genes within the most negatively related module.

Conclusions

Our study illustrates an overview of gene expression changes in human atrial samples from patients undergoing CABG surgery and might help translate future research into clinical work.

The Effect of Remote Ischemic Preconditioning on the Incidence of Acute Kidney Injury in Patients Undergoing Coronary Artery Bypass Graft Surgery: A Randomized Controlled Trial

BACKGROUND

Remote ischemic preconditioning (RIPC) protects other organs from subsequent lethal ischemic injury, but uncertainty remains. We investigated if RIPC could prevent acute kidney injury (AKI) in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

This parallel-group, double-blind, randomized, controlled trial was done on adults undergoing elective or urgent on-pump CABG surgery from 2013 to 2017 in Shiraz, Iran. Patients were allocated to RIPC or control groups through permuted blocking. The patients in the RIPC group received three cycles of 5 min ischemia and 5 min reperfusion in the upper arm after induction of anesthesia. We placed an uninflated cuff on the arm for 30 min in the control group. The study primary endpoint was an incidence of AKI. Secondary endpoints included short-term clinical outcomes. We compared categorical and continuous variables using Pearson χ2 and unpaired t tests, respectively. P<0.05 was considered significant.

RESULTS

of the 180 patients randomized to RIPC (n=90) and control (n=90) groups, 87 patients in the RIPC and 90 patients in the control group were included in the analysis. There was no significant difference in the incidence of AKI between the groups (38 patients [43.7%] in the RIPC group and 41 patients [45.6%] in the control group; relative risk, 0.96; 95% confidence interval, 0.69 to 1.33; P=0.80). No significant differences were seen regarding secondary endpoints such as postoperative liver function, atrial fibrillation, and inpatient mortality.

CONCLUSION

RIPC did not reduce the incidence of AKI, neither did it improve short-term clinical outcomes in patients undergoing on-pump CABG surgery. Trial Registration Number: IRCT2017110537254N1.

Combined Ischemic Postconditioning and Ozone Postconditioning Provides Synergistic Protection Against Renal Ischemia and Reperfusion Injury Through Inhibiting Pyroptosis

OBJECTIVE

To investigate whether ischemic postconditioning (IPO) and ozone postconditioning (OP) could synergistically attenuate renal ischemia-reperfusion (I/R) injury and its possible mechanism.

MATERIALS AND METHODS

An in vivo rat model of renal I/R injury was established, and the serum and kidneys were harvested after reperfusion to assess renal function and histologic changes. For the in vitro study, the cultured NRK-52E cells were subjected to 3 hours of hypoxia (5% CO₂, 1% O₂, and 94% N₂) followed by 24 hours of reoxygenation (5% CO₂, 21% O₂, and 74% N₂). The mRNA expression levels were analyzed by real-time polymerase chain reaction, and the protein expression levels were analyzed by using Western blot, immunofluorescence staining and enzyme-linked immunosorbent assay.

RESULTS

Kidneys undergone I/R showed characteristic renal dysfunction and pyroptosis. IPO or OP could prevent the elevated blood urea nitrogen and creatinine, renal damage, as well as pyroptosis, however, the combined application of them had more obvious protection. Oxidative stress and pyroptosis were increased in hypoxia and reoxygenation (H/R) model using NRK-52E cells. The combination of hypoxic postconditioning and OP had more protective effects on oxidative abnormalities and pyroptosis compared with the single application of hypoxic postconditioning or OP.

CONCLUSION

Our in vivo and in vitro studies show the combination of IPO and OP synergistically prote-cted the kidney from I/R by attenuating pyroptosis in kidney cells.

Is there a role for ischaemic conditioning in cardiac surgery?

Coronary artery disease (CAD) is a major cause of morbidity and mortality worldwide. Coronary artery bypass graft (CABG) surgery is the revascularisation strategy of choice in patients with diabetes mellitus and complex CAD. Owing to a number of factors, including the ageing population, the increased complexity of CAD being treated, concomitant valve and aortic surgery, and multiple comorbidities, higher-risk patients are being operated on, the result of which is an increased risk of sustaining perioperative myocardial injury (PMI) and poorer clinical outcomes. As such, new treatment strategies are required to protect the heart against PMI and improve clinical outcomes following cardiac surgery. In this regard, the heart can be endogenously protected from PMI by subjecting the myocardium to one or more brief cycles of ischaemia and reperfusion, a strategy called "ischaemic conditioning". However, this requires an intervention applied directly to the heart, which may be challenging to apply in the clinical setting. In this regard, the strategy of remote ischaemic conditioning (RIC) may be more attractive, as it allows the endogenous cardioprotective strategy to be applied away from the heart to the arm or leg by simply inflating and deflating a cuff on the upper arm or thigh to induce one or more brief cycles of ischaemia and reperfusion (termed "limb RIC"). Although a number of small clinical studies have demonstrated less PMI with limb RIC following cardiac surgery, three recently published large multicentre randomised clinical trials found no beneficial effects on short-term or long-term clinical outcomes, questioning the role of limb RIC in the setting of cardiac surgery. In this article, we review ischaemic conditioning as a therapeutic strategy for endogenous cardioprotection in patients undergoing cardiac surgery and discuss the potential reasons for the failure of limb RIC to improve clinical outcomes in this setting. Crucially, limb RIC still has the therapeutic potential to protect the heart in other clinical settings, such as acute myocardial infarction, and it may also protect other organs against acute ischaemia/reperfusion injury (such as the brain, kidney, and liver).

The Effect of Remote Ischemic Conditioning and Glyceryl Trinitrate on Perioperative Myocardial Injury in Cardiac Bypass Surgery Patients: Rationale and Design of the ERIC-GTN Study

Remote ischemic conditioning (RIC) using transient limb ischemia/reperfusion has been reported to reduce perioperative myocardial injury in patients undergoing coronary artery bypass grafting and/or valve surgery. The role of intravenous glyceryl trinitrate (GTN) therapy administered during cardiac surgery as a cardioprotective agent and whether it interferes with RIC cardioprotection is not clear and is investigated in the ERIC-GTN trial ( http://www.clinicaltrials.gov: NCT01864252). The ERIC-GTN trial is a single-site, double-blind, randomized, placebo-controlled study. Consenting adult patients (age > 18 years) undergoing elective coronary artery bypass grafting ± valve surgery with blood cardioplegia will be eligible for inclusion. Two hundred sixty patients will be randomized to 1 of 4 treatment groups following anesthetic induction: (1) RIC alone, a RIC protocol comprising three 5-minute cycles of simultaneous upper-arm and thigh cuff inflation/deflation followed by an intravenous (IV) placebo infusion; (2) GTN alone, a simulated sham RIC protocol followed by an IV GTN infusion; (3) RIC + GTN, a RIC protocol followed by an IV GTN infusion; and (4) neither RIC nor GTN, a sham RIC protocol followed by IV placebo infusion. The primary endpoint will be perioperative myocardial injury as quantified by the 72-hour area-under-the-curve serum high-sensitivity troponin T. The ERIC-GTN trial will determine whether intraoperative GTN therapy is cardioprotective during cardiac surgery and whether it affects RIC cardioprotection.

A Double Blind Randomized Clinical Trial of Remote Ischemic Conditioning in Live Donor Renal Transplantation

Ischemic conditioning involves the delivery of short cycles of reversible ischemic injury in order to induce protection against subsequent more prolonged ischemia. This randomized controlled trial was designed to determine the safety and efficacy of remote ischemic conditioning (RC) in live donor kidney transplantation.This prospective randomized clinical trial, 80 patients undergoing live donor kidney transplantation were randomly assigned in a 1:1 ratio to either RC or to a control group. RC consisted of cycles of lower limb ischemia induced by an arterial tourniquet cuff placed around the patient's thigh. In the RC treatment group, the cuff was inflated to 200 mm Hg or systolic pressure +25 mm Hg for 4 cycles of 5 min ischemia followed by 5 min reperfusion. In the control group, the blood pressure cuff was inflated to 25 mm Hg. Patients and medical staff were blinded to treatment allocation. The primary end-point was renal function measured by estimated glomerular filtration rate (eGFR) at 1 and 3 months posttransplant.Donor and recipient demographics were similar in both groups (P < 0.05). There were no significant differences in eGFR at 1 month (control 52 ± 14 vs RC 54 ± 17 mL/min; P = 0.686) or 3 months (control 50 ± 14 vs RC 49 ± 18 mL/min; P = 0.678) between the control and RC treatment groups. The RC technique did not cause any serious adverse effects.RC, using the protocol described here, did not improve renal function after live donor kidney transplantation.

Ischemic postconditioning attenuates inflammation in rats following renal ischemia and reperfusion injury

Ischemic postconditioning (IPoC) involves a series of brief rapid intermittent ischemic episodes applied at the onset of reperfusion in the previously ischemic tissue or organ. Previous studies have demonstrated that IPoC attenuates tissue damage induced by ischemia and reperfusion (I/R) injury. The aim of the present study was to investigate whether IPoC has a beneficial effect on inflammation in a rat model of renal I/R injury. Wistar rats were subjected to 45 min of ischemia followed by 24, 72 or 120 h of reperfusion (I/R group). In the IPoC group, rats subjected to I/R were treated with six cycles of 10 sec reperfusion followed by a 10-sec ischemic episode. Blood samples were collected for the determination of blood urea nitrogen (BUN) and creatinine (Cr) levels. Furthermore, histological examination and immunohistochemical staining for the localization of nuclear factor-κB (NF-κB) were performed. In addition, quantitative polymerase chain reaction (qPCR) analysis was used to determine the expression levels of intercellular adhesion molecule-1 (ICAM-1), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), while western blot analysis was used to detect the protein expression levels of NF-κB. The results indicated that the BUN and Cr levels increased significantly in the I/R group, while the IPoC rats showed evidently reduced renal damage. Immunohistochemical analysis revealed that the expression levels of NF-κB were decreased by IPoC. In addition, the qPCR results revealed that IPoC significantly inhibited the increased mRNA expression levels of ICAM-1, IL-6 and TNF-α, induced by I/R injury. Western blot analysis indicated that the expression levels of NF-κB were upregulated in the I/R group, while IPoC was shown to inhibit the expression. In conclusion, IPoC was demonstrated to exhibit potent anti-inflammatory properties against renal I/R injury.

Cardio-protective signalling by glyceryl trinitrate and cariporide in a model of donor heart preservation

BACKGROUND

Storage of donor hearts in cardioplegic solutions supplemented with agents that mimic the ischaemic preconditioning response enhanced their post-reperfusion function. The present study examines the minimisation of cell death and activation of pro-survival signalling directed towards maintenance of mitochondrial homeostasis in hearts arrested and stored in two such agents, glyceryl-trinitrate, a nitric oxide donor and cariporide, (a sodium-hydrogen exchange inhibitor).

METHODS

After baseline functional measurement, isolated working rat hearts were arrested and stored for 6h at 4°C in either Celsior(®), Celsior(®) containing 0.1mg/ml glyceryl-trinitrate, 10μM cariporide or both agents. After reperfusion, function was remeasured. Hearts were then processed for immunoblotting or histology.

RESULTS

Necrotic and apoptotic markers present in the Celsior(®) group post-reperfusion were abolished by glyceryl-trinitrate, cariporide or both. Increased phosphorylation of ERK and Bcl2, after reperfusion in groups stored in glyceryl-trinitrate, cariporide or both along with increased phospho-STAT3 levels in the glyceryl-trinitrate/cariporide group correlated with functional recovery. Inhibition of STAT3 phosphorylation blocked recovery. No phospho-Akt increase was seen in any treatment.

CONCLUSIONS

Activation of signalling pathways that favour mitophagy activation (ERK and Bcl2 phosphorylation) and maintenance of mitochondrial transition pore closure after reperfusion (STAT3 and ERK phosphorylation) were crucial for functional recovery of the donor heart.

Novel therapeutic strategies for cardioprotection

The morbidity and mortality from ischemic heart disease (IHD) remain significant worldwide. The treatment for acute myocardial infarction has improved over the past decades, including early reperfusion of occluded coronary arteries. Although it is essential to re-open the artery as soon as possible, paradoxically this leads to additional myocardial injury, called acute ischemia-reperfusion injury (IRI), for which currently no effective therapy is available. Therefore, novel therapeutic strategies are required to protect the heart from acute IRI in order to reduce myocardial infarction size, preserve cardiac function and improve clinical outcomes in patients with IHD. In this review article, we will first outline the pathophysiology of acute IRI and review promising therapeutic strategies for cardioprotection. These include novel aspects of mitochondrial function, epigenetics, circadian clocks, the immune system, microvesicles, growth factors, stem cell therapy and gene therapy. We discuss the therapeutic potential of these novel cardioprotective strategies in terms of pharmacological targeting and clinical application.

Understanding innovations in the evolving practice of blood and crystalloid cardioplegia

The use of cardioplegia solution has substantially increased the safety of cardiac surgery. It protects the myocardium by inducing a rapid and complete diastolic arrest, minimizing myocardial energy requirements, preventing ischaemic damage during the arrest phase and minimizing or preventing reperfusion injury once coronary blood flow is restored. This article is a summary of important information that has accumulated in the literature about cardioplegia and describes how our understanding of cardioplegia has evolved. The basic principles of myocardial ischaemia and reperfusion injury and how they relate to myocardial protection are described. Blood and crystalloid cardioplegia are compared with respect to biochemical and physiological differences. Recent patient demographic changes, with surgeons operating on older, more complex patients who have more severe and diffuse disease, are discussed. This cohort of patients potentially requires prolonged elective ischaemia; hence, improved myocardial protection would be of benefit. We highlight areas of study that have demonstrated a new concept of myocardial protection, known as polarized arrest. Many pharmacological agents have been shown (in experimental studies) to have the ability to induce a polarized arrest and to provide improved protection.

The effect of cyclosporin-A on peri-operative myocardial injury in adult patients undergoing coronary artery bypass graft surgery: a randomised controlled clinical trial

Objective

Cyclosporin-A (CsA) has been reported to reduce myocardial infarct size in both the experimental and clinical settings. This protective effect is dependent on its ability to prevent the opening of the mitochondrial permeability transition pore, a critical determinant of cell death in the setting of acute ischaemia-reperfusion injury. Whether CsA can reduce the extent of peri-operative myocardial injury (PMI) in patients undergoing coronary artery bypass graft (CABG) surgery is unknown, and is investigated in this randomised controlled clinical trial.

Methods

78 adult patients undergoing elective CABG surgery were randomised to receive either an intravenous bolus of CsA (2.5 mg/kg) or placebo administered after induction of anaesthesia and prior to sternotomy. PMI was assessed by measuring serum cardiac enzymes, troponin T (cTnT) and CK-MB at 0, 6, 12, 24, 48 and 72 h after surgery.

Results

There was no significant difference in mean peak cTnT levels between control (n=43) and CsA treatment (n=40) patients (0.56±0.06 ng/mL with control vs 0.35±0.05 ng/mL with CsA; p=0.07). However, in higher-risk patients with longer cardiopulmonary bypass times, there was a significant reduction in PMI with CsA therapy (p=0.049), with a reduced postoperative cTnT rise by 0.03 ng/mL for every 10 min, when compared with control.

Conclusions

In patients with longer cardiopulmonary bypass times, a single intravenous bolus of CsA administered prior to CABG surgery reduced the extent of PMI.

Protection against renal ischemia-reperfusion injury by ischemic postconditioning

Ischemia-reperfusion injury (IRI) is inevitable during transplantation. Attempts to reduce IRI have mainly focused on ways to improve hypothermic organ preservation and reduce the nephrotoxic effects of calcineurin inhibitors. Recently, it has been shown that short, repeated sequences of intermittent ischemia and reperfusion after a prolonged ischemic episode, so-called ischemic postconditioning (IPoC), reduce myocardial infarct size by approximately 40% in animal models and in humans. The principle of IPoC could be applied to every organ after ischemic injury, including kidney transplants. In fact, IPoC has demonstrated its clinical potential by reducing IRI in different organs in several animal models. In this review, we provide an overview of animal experiments on renal IRI and IPoC, demonstrating benefits with respect to organ damage and kidney function. We propose potential mechanisms by which IPoC protects against IRI. However, thus far, no human trials investigating IPoC in transplantation have been performed. Such clinical studies are needed to establish whether a simple procedure such as IPoC can improve the outcomes of human organ transplantation.

Translating cardioprotection for patient benefit: position paper from the Working Group of Cellular Biology of the Heart of the European Society of Cardiology

Coronary heart disease (CHD) is the leading cause of death and disability worldwide. Despite current therapy, the morbidity and mortality for patients with CHD remains significant. The most important manifestations of CHD arise from acute myocardial ischaemia-reperfusion injury (IRI) in terms of cardiomyocyte death and its long-term consequences. As such, new therapeutic interventions are required to protect the heart against the detrimental effects of acute IRI and improve clinical outcomes. Although a large number of cardioprotective therapies discovered in pre-clinical studies have been investigated in CHD patients, few have been translated into the clinical setting, and a significant number of these have failed to show any benefit in terms of reduced myocardial infarction and improved clinical outcomes. Because of this, there is currently no effective therapy for protecting the heart against the detrimental effects of acute IRI in patients with CHD. One major factor for this lack of success in translating cardioprotective therapies into the clinical setting can be attributed to problems with the clinical study design. Many of these clinical studies have not taken into consideration the important data provided from previously published pre-clinical and clinical studies. The overall aim of this ESC Working Group Cellular Biology of the Heart Position Paper is to provide recommendations for optimizing the design of clinical cardioprotection studies, which should hopefully result in new and effective therapeutic interventions for the future benefit of CHD patients.

Cardioprotective effect of transcutaneous electric acupoint stimulation in the pediatric cardiac patients: a randomized controlled clinical trial

BACKGROUND

Acupuncture pretreatment exerts neuroprotective and cardioprotective effects in animal models and in adult patients underwent cardiac surgery; however, data in pediatric patient are unavailable.

OBJECTIVE/AIM

To investigate the effects of transcutaneous electric acupoint stimulation (TEAS) on acute myocardial injury from pediatric open-heart surgery.

METHODS

Children, aged 2-12 years, with congenital heart defects scheduled for surgical repair were enrolled. They were randomized to TEAS (administrated at bilateral P6 acupoint for 30 min after basal anesthesia) and control (an electrode was placed on the arm without stimulus) groups. The primary end point was serum cardiac troponin I (cTnI) over 24 h after aortic unclamping. Furthermore, clinical outcome and serum cytokine and C-reactive protein concentrations were evaluated.

RESULTS

Seventy eligible children were analyzed, 36 in controls and 34 in TEAS group. Compared with controls, the mean cTnI levels were significantly lower in TEAS group at 8 h (P = 0.043) and 24 h (P = 0.046) after aortic unclamping. The duration of ventilation (P = 0.004) and length of ICU stay (P = 0.032) was significantly longer in controls than in TEAS group. There was a significant difference in the release of C-reactive protein at 8 h (P = 0.039) between two groups, whereas the values for cytokines were not significant.

CONCLUSION

Transcutaneous electric acupoint stimulation on the bilateral P6 acupoint is effective for attenuation myocardial injury in children undergoing cardiac surgery. The beneficial effects may be partially associated with reduction in cTnI and C-reactive protein level in the early postoperative period.

The effects of hydrogen sulfide under sevoflurane administration against ischemia and reperfusion injury in isolated rat heart

Background

Hydrogen sulfide (H₂S) produces a protective effect against myocardial ischemia and reperfusion injury. Sevoflurane, which is used for anesthesia in cardiac problem patients, also has a protective effect. This study is designed to reveal the effects of H₂S under sevoflurane using rat hearts.

Methods

The hearts were Langendorff-perfused, subjected to 30 minutes ischemia and 60 minutes reperfusion. Group I was a control group. The other groups were pretreated for 15 minutes before ischemia as follows: 1.6% sevoflurane for group S; 18.5 µM H₂S S for group H; and 1.6% sevoflurane and 18.5 µM H₂S simultaneously for group HS. Hemodynamics and the infarct size were measured.

Results

Group HS presented depressed hemodynamics during pretreatment. LV function in group HS achieved better recovery than group I after reperfusion. The infarct size of groups S, H and HS was smaller than group I, while there were no differences between groups S, H and HS.

Conclusions

Exogenous H₂S did not enhance the preconditioning effects of sevoflurane. Rather, the results suggest that H₂S under sevoflurane might depress hemodynamics.

Failure to recapture cardioprotection with high-dose atorvastatin in coronary artery bypass surgery: a randomised controlled trial

The acute administration of atorvastatin has been reported to reduce myocardial infarct size in animal studies. However, this cardioprotective effect is lost with the chronic administration of atorvastatin, although it can be recaptured by administering an acute high-dose of atorvastatin. We hypothesised that pre-treatment with high-dose atorvastatin, on a background of chronic standard 'statin' therapy, would reduce myocardial injury in patients undergoing elective coronary artery bypass graft (CABG) surgery. One hundred and one consenting patients undergoing elective CABG surgery at a single tertiary cardiac centre were recruited into two randomised controlled, single-blinded clinical studies. Study 1: 45 patients were randomised to receive either 160 mg of atorvastatin 2 h preoperatively and 24 h following surgery or their standard statin therapy. Study 2: 56 patients were randomised to receive either 160 mg of atorvastatin 12 h preoperatively and 24 h following surgery or their standard statin therapy. Blood samples for troponin T and creatine kinase were taken prior to surgery and then at 6, 12, 24, 48 and 72 h post-surgery. Cardiac enzyme levels at each time point and the total area-under curve (AUC) were calculated. The group characteristics and surgical methods were well matched. High-dose atorvastatin was not associated with any significant side effects. There was no significant difference in serum troponin T or creatine kinase in either study at each time point or over 72 h. Study 1: AUC, troponin T: atorvastatin 29.6 ± 34.8 μg/L versus control 25.0 ± 22.0 μg/L:P > 0.05. Creatine kinase: atorvastatin 33,544 ± 20,063 IU/L versus control 30,620 ± 10,776 IU/L:P > 0.05. Study 2: AUC, troponin T: atorvastatin 21.8 ± 14.3 μg/L versus control 20.9 ± 8.7 μg/L:P > 0.05. Creatine kinase: atorvastatin 36,262 ± 28,821 IU/L versus control 33,448 ± 14,984:P > 0.05. There were no differences in postoperative outcomes. We report that the administration of high-dose atorvastatin to low risk patients undergoing elective CABG surgery, who are already on standard dose 'statin' therapy is safe, but does not further reduce perioperative myocardial injury.

The therapeutic potential of ischemic conditioning: an update

Novel approaches are required to improve clinical outcomes in patients with coronary heart disease (CHD). Ischemic conditioning--the practice of applying brief episodes of nonlethal ischemia and reperfusion to confer protection against a sustained episode of lethal ischemia and reperfusion injury--is one potential therapeutic strategy. Importantly, the protective stimulus can be applied before (ischemic preconditioning) or after (ischemic perconditioning) onset of the sustained episode of lethal ischemia, or even at the onset of myocardial reperfusion (ischemic postconditioning). Furthermore, the protective stimulus can be applied noninvasively by placing a blood-pressure cuff on an upper or lower limb to induce brief episodes of nonlethal ischemia and reperfusion (remote ischemic conditioning), a finding that has greatly facilitated the translation of ischemic conditioning to various clinical settings. In addition to mechanical approaches, elucidation of the signal-transduction pathways underlying ischemic conditioning has identified several novel targets for pharmacological conditioning. This Review highlights findings from proof-of-concept clinical studies conducted in the past 5-6 years, in which the therapeutic potential of ischemic and pharmacological conditioning has been realized. Large, randomized, controlled trials are now required to determine whether pharmacological and ischemic conditioning improve clinical end points and outcomes in patients with CHD.

A comparison of cardiac post-conditioning and remote pre-conditioning in paediatric cardiac surgery

BACKGROUND

Remote ischaemic pre-conditioning and cardiac ischaemic post-conditioning provide myocardial protection in cardiac surgery. However, these two endogenous strategies have not been directly compared in a clinical setting. The purpose of this study was to compare the efficacy of remote ischaemic pre-conditioning and post-conditioning in providing myocardial protection to children undergoing cardiopulmonary bypass for surgical repair of ventricular septal defect.

METHODS

We randomly assigned 60 paediatric patients scheduled for surgical correction of congenital ventricular septal defect to the post-conditioning group (n = 20), remote pre-conditioning group (n = 20), or control group (n = 20). Post-conditioning consisted of 30 seconds of ischaemia and 30 seconds of reperfusion achieved by clamping and unclamping the aorta, repeated three times over 3 minutes immediately after cardioplegic arrest. Remote ischaemic pre-conditioning consisted of 5 minutes of lower limb ischaemia followed by 5 minutes of reperfusion using a blood-pressure cuff inflated to a pressure of 200 millimetres of mercury, also repeated three times over 30 minutes. We assayed creatine kinase-MB, troponin I.

RESULTS

Mean age, cardiopulmonary bypass times, and aortic cross-clamp times were matched across groups. Both post-conditioning and remote ischaemic pre-conditioning reduced the peak release of creatine kinase-MB (86.1 plus or minus 24.1 units per litre and 92.8 plus or minus 20.6 units per litre, respectively, versus 111.0 plus or minus 44.6 units per litre in the control, p less than 0.05) and troponin I (0.28 plus or minus 0.10 nanogram per millilitre and 0.26 plus or minus 0.09 nanogram per millilitre, respectively, versus 0.49 plus or minus 0.19 nanogram per millilitre in the control group, p less than 0.05).

CONCLUSIONS

Our study demonstrates that ischaemic post-conditioning and remote ischaemic pre-conditioning provide comparable myocardial benefit in children undergoing cold blood cardioplegic arrest.

Remote ischemic preconditioning in human coronary artery bypass surgery: from promise to disappointment?

BACKGROUND

We assessed whether remote ischemic preconditioning (RIPC) improves myocardial, renal, and lung protection after on-pump coronary surgery.

METHODS AND RESULTS

This was a single-center, prospective, randomized (1:1), placebo-controlled trial. Patients, investigators, anesthetists, surgeons, and critical care teams were blinded to group allocation. Subjects received RIPC (or placebo) stimuli (×3 upper limb (or dummy arm), 5-minute cycles of 200 mm Hg cuff inflation/deflation) before aortic clamping. Anesthesia, perfusion, cardioplegia, and surgical techniques were standardized. The primary end point was 48-hour area under the curve (AUC) troponin T (cTnT) release. Secondary end points were 6-hour and peak cTnT, ECG changes, cardiac index, inotrope and vasoconstrictor use, renal dysfunction, and lung injury. Hospital survival was 99.4%. Comparing placebo and RIPC, median (interquartile range) AUC 48-hour cTnT (ng/mL(-1)/48 h(-1)); 28 (19, 39) versus 30 (22, 38), 6-hour cTnT (ng/mL(-1)); 0.93(0.59, 1.35) versus 1.01(0.72, 1.43), peak cTnT (ng/mL(-1)); 1.02 (0.74, 1.44) versus 1.04 (0.78, 1.51), de novo left bundle-branch block (4% versus 0%) and Q waves (5.3% versus 5.5%), serial cardiac indices, intraaortic balloon pump usage (8.5% versus 7.5%), inotrope (39% versus 50%) and vasoconstrictor usage (66% versus 64%) were not different. Dialysis requirement (1.2% versus 3.8%), peak creatinine (median [interquartile range], 1.2 mg/dL(-1) (1.1, 1.4) versus 1.2 (1.0, 1.4)), and AUC urinary albumin-creatinine ratios 69 (40, 112) versus 58 (32, 85) were not different. Intubation times; median (interquartile range), 937 minutes(766, 1402) versus 895(675, 1180), 6-hour; 278 (210, 338) versus 270 (218, 323) and 12-hour pO(2):FiO(2) ratios 255 (195, 323) versus 263 (210, 308) were similar.

CONCLUSIONS

In contrast to prior smaller studies, RIPC did not reduce troponin release, improve hemodynamics, or enhance renal or lung protection. Clinical Trial Registration-URL: http://www.ukcrn.org.uk. Unique identifier: 4659.

Postischemia myocardial injury in coronary artery bypass patients (PP6)

PURPOSE

To investigate the reperfusion injury of the myocardium in patients undergoing elective coronary artery bypass surgery (CABG) with cardiopulmonary bypass (CPB), we monitored the blood levels of troponin I (TNI), white blood cells, oxygen radicals, malondialdehyde, and myeloperoxidase seeking to define the relationship between the CABG-induced systemic inflammation and myocardial injury.

MATERIALS AND METHODS

We selected 10 patients undergoing primary CABG with CPB at moderate hypothermia and cardioplegic arrest concomitant with intermittent warm blood cardioplegia. We compared all data with their own baseline values to study the reperfusion injury. After release of the aortic clamp, blood was drawn from the coronary sinus, via a catheter placed through the right atrium. We measured plasma levels of inflammatory mediators, such as malondialdehyde, myeloperoxidase, oxygen radicals, and the myocardium injury parameter of TNI.

RESULTS

Patients showed no difference concerning aortic clamp time. TNI increased significantly at 1, 15, and 30 minutes after the onset of reperfusion. Blood levels of white blood cells, oxygen radicals, malondialdehyde, and myeloperoxidase also increased significantly with reperfusion time.

CONCLUSIONS

Reperfusion of ischemic myocardium induced increased TNI, which may be related to the systemic inflammatory responses induced by ischemia and reperfusion of the myocardium among patients undergoing elective coronary bypass surgery.