Co-morbidities and co-medications as confounders of cardioprotection-Does it matter in the clinical setting?

Inhibition of the protective effects of preconditioning in ischemia-reperfusion injury by chronic methadone: the role of pAkt and pSTAT3

Cardiac ischemic preconditioning (Pre) reduces cardiac ischemia-reperfusion injury (IRI) by stimulating opioid receptors. Chronic use of opioids can alter the signaling pathways. We investigated the effects of chronic methadone use on IRI and Pre. The experiments were performed on isolated hearts of male Wistar rats in four groups: IRI, Methadone + IRI (M-IRI), Pre + IRI (Pre-IRI), Methadone + Pre + IRI (M-Pre-IRI). The infarct size (IS) in the Pre-IRI group was smaller than the IRI group (26.8% vs. 47.8%, P < 0.05). In the M-IRI and M-Pre-IRI groups, the infarct size was similar to the IRI group. Akt (Ak strain transforming) phosphorylation in the Pre-IRI, M-IRI, and M-Pre-IRI groups was significantly higher than in the IRI group (0.56 ± 0.15, 0.63 ± 0.20, and 0.93 ± 0.18 vs 0.28 ± 0.17 respectively). STAT3 (signal transducer and activator of transcription 3) phosphorylation in the Pre-IRI and M-Pre-IRI groups (1.38 ± 0.14 and 1.46 ± 0.33) was significantly higher than the IRI and M-IRI groups (0.99 ± 0.1 and 0.98 ± 0.2). Thus, chronic use of methadone not only has no protective effect against IRI but also destroys the protective effects of ischemic preconditioning. This may be due to the hyperactivation of Akt and changes in signaling pathways.

Cardioprotection with Intralipid During Coronary Artery Bypass Grafting Surgery on Cardiopulmonary Bypass: A Randomized Clinical Trial

PURPOSE

Coronary artery bypass grafting (CABG) on cardiopulmonary bypass (CPB) is associated with myocardial ischemia-reperfusion injury (IRI), which may limit the benefit of the surgery. Both experimental and clinical studies suggest that Intralipid, a lipid emulsion commonly used for parenteral nutrition, can limit myocardial IRI. We therefore aimed to investigate whether Intralipid administered at reperfusion can reduce myocardial IRI in patients undergoing CABG on CPB.

METHODS

We conducted a randomized, double-blind, pilot trial in which 29 adult patients scheduled for CABG were randomly assigned (on a 1:1 basis) to receive either 1.5 ml/kg Intralipid 20% or Ringer's Lactate 3 min before aortic cross unclamping. The primary endpoint was the 72-h area under the curve (AUC) for troponin I.

RESULTS

Of the 29 patients randomized, 26 were included in the study (two withdrew consent and one was excluded before surgery). The 72-h AUC for troponin I did not significantly differ between the control and Intralipid group (546437 ± 205518 versus 487561 ± 115724 arbitrary units, respectively; P = 0.804). Other outcomes (including 72-h AUC for CK-MB, C-reactive protein, need for defibrillation, time to extubation, length of ICU and hospital stay, and serious adverse events) were similar between the two groups.

CONCLUSION

In patients undergoing CABG on CPB, Intralipid did not limit myocardial IRI compared to placebo.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02807727 (registration date: 16 June 2016).

Malonate given at reperfusion prevents post-myocardial infarction heart failure by decreasing ischemia/reperfusion injury

The mitochondrial metabolite succinate is a key driver of ischemia/reperfusion injury (IRI). Targeting succinate metabolism by inhibiting succinate dehydrogenase (SDH) upon reperfusion using malonate is an effective therapeutic strategy to achieve cardioprotection in the short term (< 24 h reperfusion) in mouse and pig in vivo myocardial infarction (MI) models. We aimed to assess whether inhibiting IRI with malonate given upon reperfusion could prevent post-MI heart failure (HF) assessed after 28 days. Male C57BL/6 J mice were subjected to 30 min left anterior coronary artery (LAD) occlusion, before reperfusion for 28 days. Malonate or without-malonate control was infused as a single dose upon reperfusion. Cardiac function was assessed by echocardiography and fibrosis by Masson's trichrome staining. Reperfusion without malonate significantly reduced ejection fraction (~ 47%), fractional shortening (~ 23%) and elevated collagen deposition 28 days post-MI. Malonate, administered as a single infusion (16 mg/kg/min for 10 min) upon reperfusion, gave a significant cardioprotective effect, with ejection fraction (~ 60%) and fractional shortening (~ 30%) preserved and less collagen deposition. Using an acidified malonate formulation, to enhance its uptake into cardiomyocytes via the monocarboxylate transporter 1, both 1.6 and 16 mg/kg/min 10 min infusion led to robust long-term cardioprotection with preserved ejection fraction (> 60%) and fractional shortening (~ 30%), as well as significantly less collagen deposition than control hearts. Malonate administration upon reperfusion prevents post-MI HF. Acidification of malonate enables lower doses of malonate to also achieve long-term cardioprotection post-MI. Therefore, the administration of acidified malonate upon reperfusion is a promising therapeutic strategy to prevent IRI and post-MI HF.

Cardioprotection in cardiovascular surgery

Since the invention of cardiopulmonary bypass, cardioprotective strategies have been investigated to mitigate ischemic injury to the heart during aortic cross-clamping and reperfusion injury with cross-clamp release. With advances in cardiac surgical and percutaneous techniques and post-operative management strategies including mechanical circulatory support, cardiac surgeons are able to operate on more complex patients. Therefore, there is a growing need for improved cardioprotective strategies to optimize outcomes in these patients. This review provides an overview of the basic principles of cardioprotection in the setting of cardiac surgery, including mechanisms of cardiac injury in the context of cardiopulmonary bypass, followed by a discussion of the specific approaches to optimizing cardioprotection in cardiac surgery, including refinements in cardiopulmonary bypass and cardioplegia, ischemic conditioning, use of specific anesthetic and pharmaceutical agents, and novel mechanical circulatory support technologies. Finally, translational strategies that investigate cardioprotection in the setting of cardiac surgery will be reviewed, with a focus on promising research in the areas of cell-based and gene therapy. Advances in this area will help cardiologists and cardiac surgeons mitigate myocardial ischemic injury, improve functional post-operative recovery, and optimize clinical outcomes in patients undergoing cardiac surgery.

Comparison of "Huaxi-1" or "histidine-tryptophan-ketoglutarate" cardioplegia in an animal model

Background

Using a pig model of cardiopulmonary bypass, we compared outcomes after cardioplegia either with our in-house "Huaxi-1" solution containing natural blood and crystalloid or with the entirely crystalloid, commercially available "histidine-tryptophan-ketoglutarate" solution.

Methods

Cardiopulmonary bypass was established in 12 healthy male pigs, who were randomized to receive a single dose of either Huaxi-1 or entirely crystalloid. All animals were then subjected to whole-heart ischemia for 90 min, followed by 2 h of reperfusion, after which myocardial injury was assessed in terms of cardiac function, myocardial pathology and levels of biomarkers in plasma, while levels of high-energy phosphate in myocardium were assayed using liquid chromatography.

Results

Animals given Huaxi-1 cardioplegia required significantly less time to be weaned off bypass, they received significantly lower doses of norepinephrine, and they showed significantly higher levels (mean ± SD) of adenosine triphosphate (14 ± 4 vs. 8 ± 2 µg/mg, P = 0.005), adenosine diphosphate (16 ± 2 vs. 13 ± 2 µg/mg, P = 0.046), and total adenine nucleotide (37 ± 4 vs. 30 ± 3 µg/mg, P = 0.006) in myocardium after 2 h of reperfusion. They also showed less severe bleeding, edema and injury to mitochondria and myofibers in myocardium. The two groups did not differ significantly in doses of inotropic drugs received, cardiac output or levels of biomarkers in plasma.

Conclusions

In this animal model of healthy hearts subjected to 90 min of ischemia, Huaxi-1 cardioplegia may be superior to entirely crystalloid cardioplegia for promoting energy generation and attenuating ischemia/reperfusion injury in myocardium.

Initial Despair and Current Hope of Identifying a Clinically Useful Treatment of Myocardial Reperfusion Injury: Insights Derived from Studies of Platelet P2Y12 Antagonists and Interference with Inflammation and NLRP3 Assembly

Myocardial necrosis following the successful reperfusion of a coronary artery occluded by thrombus in a patient presenting with ST-elevation myocardial infarction (STEMI) continues to be a serious problem, despite the multiple attempts to attenuate the necrosis with agents that have shown promise in pre-clinical investigations. Possible reasons include confounding clinical risk factors, the delayed application of protective agents, poorly designed pre-clinical investigations, the possible effects of routinely administered agents that might unknowingly already have protected the myocardium or that might have blocked protection, and the biological differences of the myocardium in humans and experimental animals. A better understanding of the pathobiology of myocardial infarction is needed to stem this reperfusion injury. P2Y12 receptor antagonists minimize platelet aggregation and are currently part of the standard treatment to prevent thrombus formation and propagation in STEMI protocols. Serendipitously, these P2Y12 antagonists also dramatically attenuate reperfusion injury in experimental animals and are presumed to provide a similar protection in STEMI patients. However, additional protective agents are needed to further diminish reperfusion injury. It is possible to achieve additive protection if the added intervention protects by a mechanism different from that of P2Y12 antagonists. Inflammation is now recognized to be a critical factor in the complex intracellular response to ischemia and reperfusion that leads to tissue necrosis. Interference with cardiomyocyte inflammasome assembly and activation has shown great promise in attenuating reperfusion injury in pre-clinical animal models. And the blockade of the executioner protease caspase-1, indeed, supplements the protection already seen after the administration of P2Y12 antagonists. Importantly, protective interventions must be applied in the first minutes of reperfusion, if protection is to be achieved. The promise of such a combination of protective strategies provides hope that the successful attenuation of reperfusion injury is attainable.

Exploring the therapeutic potential of tetrahydrobiopterin for heart failure with preserved ejection fraction: A path forward

A large number of patients are affected by classical heart failure (HF) symptomatology with preserved ejection fraction (HFpEF) and multiorgan syndrome. Due to high morbidity and mortality rate, hospitalization and mortality remain serious socioeconomic problems, while the lack of effective pharmacological or device treatment means that HFpEF presents a major unmet medical need. Evidence from clinical and basic studies demonstrates that systemic inflammation, increased oxidative stress, and impaired mitochondrial function are the common pathological mechanisms in HFpEF. Tetrahydrobiopterin (BH4), beyond being an endogenous co-factor for catalyzing the conversion of some essential biomolecules, has the capacity to prevent systemic inflammation, enhance antioxidant resistance, and modulate mitochondrial energy production. Therefore, BH4 has emerged in the last decade as a promising agent to prevent or reverse the progression of disorders such as cardiovascular disease. In this review, we cover the clinical progress and limitations of using downstream targets of nitric oxide (NO) through NO donors, soluble guanylate cyclase activators, phosphodiesterase inhibitors, and sodium-glucose co-transporter 2 inhibitors in treating cardiovascular diseases, including HFpEF. We discuss the use of BH4 in association with HFpEF, providing new evidence for its potential use as a pharmacological option for treating HFpEF.

Is There a Mitochondrial Protection via Remote Ischemic Conditioning in Settings of Anticancer Therapy Cardiotoxicity?

PURPOSE OF REVIEW

To provide an overview of (a) protective effects on mitochondria induced by remote ischemic conditioning (RIC) and (b) mitochondrial damage caused by anticancer therapy. We then discuss the available results of studies on mitochondrial protection via RIC in anticancer therapy-induced cardiotoxicity.

RECENT FINDINGS

In three experimental studies in healthy mice and pigs, there was a RIC-mediated protection against anthracycline-induced cardiotoxicity and there was some evidence of improved mitochondrial function with RIC. The RIC-mediated protection was not confirmed in the two available studies in cancer patients. In adult cancer patients, RIC was associated with an adverse outcome. There are no data on mitochondrial function in cancer patients. Studies in tumor-bearing animals are needed to determine whether RIC does not interfere with the anticancer properties of the drugs and whether RIC actually improves mitochondrial function, ultimately resulting in improved cardiac function.

Using mechanism-based combinations of H2S-donors to maximize the cardioprotective action of H2S

H2S-donors are cardioprotective in ischemia/reperfusion (I/R) injury. Some H2S-donors exert their beneficial effects in a nitric oxide (NO)-dependent manner, while others act using NO-independent pathways. The aims of the present study were to (i) evaluate whether H2S-donors with distinct pharmacodynamic properties act synergistically in I/R injury and (ii) determine if H2S-donors remain cardioprotective in obese mice. C57BL/6 mice were subjected to 30 min of ischemia followed by 120 min of reperfusion. Donors were administered intravenously at the end of ischemia (Na2S: 1 μmol/kg, GYY4137: 25 μmol/kg, AP39: 0,25 μmol/kg), while the 3-mercaptopyruvate sulfurtransferase (10 mg/kg) inhibitor was given intraperitonially 1 h prior to ischemia. Infarct size was estimated by 2,3,5-triphenyltetrazolium staining, while the area at risk was calculated using Evans blue. All three donors reduced infarct size when administered as a sole treatment. Co-administration of Na2S/GYY4137, as well as Na2S/AP39 reduced further the I/R injury, beyond what was observed with each individual donor. Since inhibition of the H2S-producing enzyme 3-mercaptopyruvate sulfurtransferase is known to reduce infarct size, we co-administered C3 with Na2S to determine possible additive effects between the two agents. In this case, combination of C3 with Na2S did not yield superior results compared to the individual treatments. Similarly, to what was observed in healthy mice, administration of a H2S-donor (Na2S or AP39) reduced I/R injury in mice rendered obese by consumption of a high fat diet. We conclude that combining a NO-dependent with a NO-independent H2S-donor leads to enhanced cardioprotection and that H2S-donors remain effective in obese animals.

Cardioprotective effect of naringin against the ischemia/reperfusion injury of aged rats

Aging is known as a main risk factor in the development of cardiovascular diseases. Naringin (NRG) is a flavonoid compound derived from citrus fruits. It possesses a wide spectrum of pharmacological properties, including antioxidant anti-inflammatory, and cardioprotective. This investigation aimed to assess the cardioprotective effect of NRG against the ischemia/reperfusion (I/R) injury in aged rats. In this study, D-galactose (D-GAL) at the dose of 150 mg/kg/day for 8 weeks was used to induce aging in rats. Rats were orally gavaged with NRG (40 or 100 mg/kg/day), in co-treatment with D-GAL, for 8 weeks. The Langendorff isolated heart was used to evaluate the effect of NRG on I/R injury in aged rats. NRG treatment diminished myocardial hypertrophy and maximum contracture level in aged animals. During the pre-ischemic phase, reduced heart rate was normalized by NRG. The effects of D-GAL on the left ventricular end diastolic pressure (LVDP), the rate pressure product (RPP), and the minimum and maximum rate of left ventricular pressure (±dp/dt) improved by NRG treatment in the perfusion period. NRG also enhanced post-ischemic recovery of cardiac functional parameters (± dp/dt, and RPP) in isolated hearts. An increase in serum levels of the lactate dehydrogenase (LDH), the creatine kinase-MB (CK-MB), and the tumor necrosis factor-alpha (TNF-α) were reversed by NRG in aged rats. It also normalized the D-GAL-decreased the superoxide dismutase (SOD) activity in the heart tissue. NRG treatment alleviated cardiac injury in aged hearts under conditions of I/R. NRG may improve aging-induced cardiac dysfunction through anti-oxidative and anti-inflammatory mechanisms.

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Platelet-Mediated Transfer of Cardioprotection by Remote Ischemic Conditioning and Its Abrogation by Aspirin But Not by Ticagrelor

PURPOSE

The role of platelets during myocardial ischemia/reperfusion (I/R) is ambivalent. They contribute to injury but also to cardioprotection. Repeated blood flow restriction and reperfusion in a tissue/organ remote from the heart (remote ischemic conditioning, RIC) reduce myocardial I/R injury and attenuate platelet activation. Whether or not platelets mediate RIC's cardioprotective signal is currently unclear.

METHODS AND RESULTS

Venous blood from healthy volunteers (without or with pretreatment of 500/1000 mg aspirin or 180 mg ticagrelor orally, 2-3 h before the study, n = 18 each) was collected before and after RIC (3 × 5 min blood pressure cuff inflation at 200 mmHg on the left upper arm/5 min deflation). Washed platelets were isolated. Platelet-poor plasma was used to prepare plasma-dialysates. Platelets (25 × 103/µL) or plasma-dialysates (1:10) prepared before and after RIC from untreated versus aspirin- or ticagrelor-pretreated volunteers, respectively, were infused into isolated buffer-perfused rat hearts. Hearts were subjected to global 30 min/120 min I/R. Infarct size was stained. Infarct size was less with infusion of platelets/plasma-dialysate after RIC (18 ± 7%/23 ± 9% of ventricular mass) than with platelets/plasma-dialysate before RIC (34 ± 7%/33 ± 8%). Aspirin pretreatment abrogated the transfer of RIC's cardioprotection by platelets (after/before RIC, 34 ± 7%/33 ± 7%) but only attenuated that by plasma-dialysate (after/before RIC, 26 ± 8%/32 ± 5%). Ticagrelor pretreatment induced an in vivo formation of cardioprotective factor(s) per se (platelets/plasma-dialysate before RIC, 26 ± 7%/26 ± 7%) but did not impact on RIC's cardioprotection by platelets/plasma-dialysate (20 ± 7%/21 ± 5%).

CONCLUSION

Platelets serve as carriers for RIC's cardioprotective signal through an aspirin-sensitive and thus cyclooxygenase-dependent mechanism. The P2Y12 inhibitor ticagrelor per se induces a humoral cardioprotective signal.

Perspective: mitochondrial STAT3 in cardioprotection

Activation of signal transducer and activator of transcription 3 (STAT3) has been identified as a key cardioprotective signal not only in animal studies but also in humans-in animals, STAT3 is causally involved in cardioprotection. In response to late ischemic conditioning, canonical function of STAT3 activation upregulates the expression of cardioprotective and anti-apoptotic proteins. In its non-canonical function, STAT3 is activated during ischemic conditioning and is part of the cardioprotective cytosolic survival activating factor enhancement pathway. Activated STAT3 is imported and localized to the mitochondria. Mitochondrial STAT3 stimulates the activity of mitochondrial electron transport chain complex I, reduces mitochondrial reactive oxygen species production and mitochondrial permeability transition pore opening. Finally, two novel aspects of STAT activation in cardioprotection are discussed: a genetic variance of the STAT encoding region as a potential primordial confounding variable for cardioprotection, and the cardioprotective potential of sodium-glucose cotransporter 2 inhibitors through STAT3 activation.

The additive effects of nicotinamide mononucleotide and melatonin on mitochondrial biogenesis and fission/fusion, autophagy, and microRNA-499 in the aged rat heart with reperfusion injury

The prognosis of myocardial ischemia/reperfusion (I/R) injury is poor in elderly patients. Aging increases the susceptibility of the heart to cell death from I/R injury and prevents the optimal effectiveness of cardioprotective modalities. Since the interaction of aging with cardioprotection is multifactorial, combination therapy may overcome the above-mentioned burden through correcting various components of the injury. Here, we explored the effects of nicotinamide mononucleotide (NMN)/melatonin combination therapy on mitochondrial biogenesis and fission/fusion, autophagy, and microRNA-499 in the aged rat heart with reperfusion injury. Ex vivo model of myocardial I/R injury was established by coronary occlusion and re-opening in 30 aged male Wistar rats (400-450 g, 22-24 months old). NMN (100 mg/kg/48 h, intraperitoneally) was administered over 28 days before I/R, and melatonin (50 µM) was added to the perfusion solution at early reperfusion. CK-MB release and expression of mitochondrial biogenesis genes and proteins, mitochondrial fission/fusion proteins, autophagy genes, and microRNA-499 were assessed. NMN/melatonin combination therapy concomitantly decreased CK-MB release in aged reperfused hearts (P < .001). It also upregulated SIRT1/PGC-1α/Nrf1/TFAM profiles at both gene and protein levels, Mfn2 protein, and microRNA-499 expression, and downregulated Drp1 protein and Beclin1, LC3, and p62 genes (P < .05 to P < .001). The effect of combination therapy was greater than individual ones. Co-application of NMN/melatonin within the setting of I/R injury in the aged rat heart induced noticeable cardioprotection through modulation of a coordinated network including microRNA-499 expression along with mitochondrial biogenesis associated with SIRT1/PGC-1α/Nrf1/TFAM profiles, mitochondrial fission/fusion, and autophagy, therefore, appears to prevent the burden of myocardial I/R injury in elderly patients.

Upregulation of P2X7 Exacerbates Myocardial Ischemia-Reperfusion Injury through Enhancing Inflammation and Apoptosis in Diabetic Mice

Diabetes-aggravated myocardial ischemia-reperfusion (MI/R) injury remains an urgent medical issue, and the molecular mechanisms involved with diabetes and MI/R injury remain largely unknown. Previous studies have shown that inflammation and P2X7 signaling participate in the pathogenesis of the heart under individual conditions. It remains to be explored if P2X7 signaling is exacerbated or alleviated under double insults. We established a high-fat diet and streptozotocin-induced diabetic mouse model, and we compared the differences in immune cell infiltration and P2X7 expression between diabetic and nondiabetic mice after 24 h of reperfusion. The antagonist and agonist of P2X7 were administered before and after MI/R. Our study showed that the MI/R injury of diabetic mice was characterized by increased infarct area, impaired ventricular contractility, more apoptosis, aggravated immune cell infiltration, and overactive P2X7 signaling compared with nondiabetic mice. The major trigger of increased P2X7 was the MI/R-induced recruitment of monocytes and macrophages, and diabetes can be a synergistic factor in this process. Administration of P2X7 agonist eliminated the differences in MI/R injury between nondiabetic mice and diabetic mice. Both 2 wk of brilliant blue G injection before MI/R and acutely administered A438079 at the time of MI/R injury attenuated the role of diabetes in exacerbating MI/R injury, as evidenced by decreased infarct size, improved cardiac function, and inhibition of apoptosis. Additionally, brilliant blue G blockade decreased the heart rate after MI/R, which was accompanied by downregulation of tyrosine hydroxylase expression and nerve growth factor transcription. In conclusion, targeting P2X7 may be a promising strategy for reducing the risk of MI/R injury in diabetes.

No robust reduction of infarct size and no-reflow by metoprolol pretreatment in adult Göttingen minipigs

Whereas prior experiments in juvenile pigs had reported infarct size reduction by intravenous metoprolol early during myocardial ischaemia, two major clinical trials in patients with reperfused acute myocardial infarction were equivocal. We, therefore, went back and tested the translational robustness of infarct size reduction by metoprolol in minipigs. Using a power analysis-based prospective design, we pretreated 20 anaesthetised adult Göttingen minipigs with 1 mg kg-1 metoprolol or placebo and subjected them to 60-min coronary occlusion and 180-min reperfusion. Primary endpoint was infarct size (triphenyl tetrazolium chloride staining) as a fraction of area at risk; no-reflow area (thioflavin-S staining) was a secondary endpoint. There was no significant reduction in infarct size (46 ± 8% of area at risk with metoprolol vs. 42 ± 8% with placebo) or area of no-reflow (19 ± 21% of infarct size with metoprolol vs. 15 ± 23% with placebo). However, the inverse relationship between infarct size and ischaemic regional myocardial blood flow was modestly, but significantly shifted downwards with metoprolol, whereas ischaemic blood flow tended to be reduced by metoprolol. With an additional dose of 1 mg kg-1 metoprolol after 30-min ischaemia in 4 additional pigs, infarct size was also not reduced (54 ± 9% vs. 46 ± 8% in 3 contemporary placebo, n.s.), and area of no-reflow tended to be increased (59 ± 20% vs. 29 ± 12%, n.s.).Infarct size reduction by metoprolol in pigs is not robust, and this result reflects the equivocal clinical trials. The lack of infarct size reduction may be the result of opposite effects of reduced infarct size at any given blood flow and reduced blood flow, possibly through unopposed alpha-adrenergic coronary vasoconstriction.

Mitoprotective effect of mesenchymal stem cells-derived conditioned medium in myocardial reperfusion injury of aged rats: role of SIRT-1/PGC-1α/NRF-2 network

BACKGROUND

The aged myocardium experiences various forms of stress that cause reduction of its tolerance to injury induced by ischemia/reperfusion (I/R). Developing effective cardioprotective modalities to prevent the amplification of I/R injury during aging is under focus of investigation. Mesenchymal stem cells (MSCs) have the ability to regenerate infarcted myocardium mostly by producing multiple secretory factors. This study aimed to explore the mechanisms of mitoprotection by MSCs-conditioned medium (CM) in myocardial I/R injury of aged rats.

METHODS

Male Wistar rats (n = 72, 400-450 g, 22-24 months old) were randomized into groups with/without I/R and/or MSCs-CM treatment. To establish myocardial I/R injury, the method of LAD occlusion and re-opening was employed. MSCs-CM was administered intramyocardially (150 μl) at the onset of reperfusion in recipient group. After 24 h reperfusion, myocardial infarct size, LDH level, mitochondrial functional endpoints, expression of mitochondrial biogenesis-associated genes, and the levels of pro-inflammatory cytokines were evaluated. After 28 days reperfusion, echocardiographic assessment of cardiac function was performed.

RESULTS

MSCs-CM treatment improved myocardial function and decreased infarct size and LDH level in aged I/R rats (P < .05 to P < .001). It also decreased mitochondrial ROS formation, enhanced mitochondrial membrane potential and ATP content, upregulated mitochondrial biogenesis-related genes including SIRT-1, PGC-1α, and NRF-2, and lessened TNF-α, IL-1β, and IL-6 levels (P < .05 to P < .01).

CONCLUSIONS

MSCs-CM treatment attenuated myocardial I/R injury in aged rats, in part by improving mitochondrial function and biogenesis and restraining inflammatory reaction. the upregulation of SIRT-1/PGC-1α/NRF-2 profiles is a possible target for the mitoprotective effects of MSCs-CM following I/R injury during aging.

Attenuation of ST-segment elevation by ischemic preconditioning: Reflection of cardioprotection in Göttingen but not in Ossabaw minipigs

BACKGROUND

Ischemic preconditioning (IPC; brief cycles of coronary occlusion/ reperfusion) reduces myocardial infarct size. The ST-segment elevation during coronary occlusion is progressively attenuated with increasing number of IPC cycles. Progressive attenuation of ST-segment elevation is considered a result of sarcolemmal K_ATP channel activation and has been considered to reflect and predict IPC's cardioprotection. We have recently demonstrated that IPC failed to reduce infarct size in minipigs of a particular strain (Ossabaw), which had a genetic predisposition to develop, but not yet established a metabolic syndrome. To determine whether or not Ossabaw minipigs nevertheless had attenuated ST-segment elevation over repetitive IPC cycles, we compared Göttingen vs. Ossabaw minipigs in which IPC reduces infarct size.

METHODS AND RESULTS

We analyzed surface chest electrocardiographic (ECG) recordings of anesthetized open-chest contemporary Göttingen (n = 43) and Ossabaw minipigs (n = 53). Both minipig strains were subjected to 60 min coronary occlusion and 180 min reperfusion without or with IPC (3 × 5 min/ 10 min coronary occlusion/ reperfusion). ST-segment elevations during the repetitive coronary occlusions were analyzed. In both minipig strains, IPC attenuated ST-segment elevation with increasing number of coronary occlusions. IPC reduced infarct size in Göttingen minipigs (45 ± 10% without vs. 25 ± 13% of area at risk with IPC), whereas such cardioprotection was absent in Ossabaw minipigs (54 ± 11% vs. 50 ± 11%).

CONCLUSION

Apparently, the block of signal transduction of IPC in Ossabaw minipigs occurs distal to the sarcolemma, where K_ATP channel activation still attenuates ST-segment elevation as it does in Göttingen minipigs.

Elamipretide mitigates ischemia-reperfusion injury in a swine model of hemorrhagic shock

ischemia-reperfusion injury (IRI) after hemorrhage is potentiated by aortic occlusion or resuscitative endovascular balloon occlusion of the aorta (REBOA). Given the central role of mitochondrial injury in shock, we hypothesized that Elamipretide, a peptide that protects mitochondria, would mitigate IRI after hemorrhagic shock and REBOA. Twelve pigs were subjected to hemorrhagic shock and 45 min of REBOA. After 25 min of REBOA, animals received either saline or Elamipretide. Animals were transfused with autologous blood during balloon deflation, and pigs were resuscitated with isotonic crystalloids and norepinephrine for 4.25 h. Elamipretide-treated animals required less crystalloids than the controls (62.5 [50-90] and 25 [5-30] mL/kg, respectively), but similar amounts of norepinephrine (24.7 [8.6-39.3] and 9.7 [2.1-12.5] mcg/kg, respectively). Treatment animals had a significant reduction in serum creatinine (control: 2.7 [2.6-2.8]; Elamipretide: 2.4 [2.4-2.5] mg/dL; p = 0.04), troponin (control: 3.20 [2.14-5.47] ng/mL, Elamipretide: 0.22 [0.1-1.91] ng/mL; p = 0.03), and interleukin-6 concentrations at the end of the study. There were no differences in final plasma lactate concentration. Elamipretide reduced fluid requirements and protected the kidney and heart after profound IRI. Further understanding the subcellular consequences of REBOA and mitochondrial rescue will open new therapeutic avenues for patients suffering from IRI after hemorrhage.

Melatonin/nicotinamide mononucleotide/ubiquinol: a cocktail providing superior cardioprotection against ischemia/reperfusion injury in a common co-morbidities modelled rat

BACKGROUND

The metabolic and intracellular abnormalities in aging and diabetes cause loss of cardioprotection by routine interventions against myocardial ischemia/reperfusion (I/R) injury. We aimed to evaluate the possible interaction of aging and type-2 diabetes mellitus with cardioprotection and the potential protective effect of a mitochondrial cocktail (melatonin/nicotinamide mononucleotide (NMN)/ubiquinol) on myocardial I/R injury in aged diabetic rats.

METHODS

Male Wistar rats (n = 108, 22-24 months old, 400-450 g) received high-fat diet/low dose of streptozotocin to induce type-2 diabetes, then were randomized into 9 groups of 12 rats each with/without I/R and/or melatonin, NMN, and ubiquinol, alone or in dual or triple combinations. Myocardial I/R was induced by LAD occlusion for 30 min followed by 24 h reperfusion. NMN (100 mg/kg/48 h, intraperitoneally) was administered for 28 days before I/R operation. Melatonin (10 mg/kg, intraperitoneally) and/or ubiquinol (30 mg/kg, intravenously) were administered at early reperfusion. Finally, hemodynamic index changes, infarct size, CK-MB levels, mitochondrial functional endpoints, and expression of mitochondrial biogenesis genes (SIRT-1/PGC-1α/NRF-2/TFAM) were assessed.

RESULTS

The solo and dual applications of melatonin, NMN, and ubiquinol did not exert remarkable cardioprotective impacts. However, the triple combination improved myocardial function and decreased infarct size and CK-MB levels following myocardial I/R (P < .05 to P < .01). It also improved mitochondrial function and restored mitochondrial biogenesis genes (P < .01).

CONCLUSIONS

Combination therapy with melatonin, NMN, and ubiquinol exerted significant cardioprotection and improved mitochondrial function and biogenesis via upregulation of SIRT-1/PGC-1α/NRF-2/TFAM profiles in aged diabetic rats and, thus, offers a promising strategy for providing noticeable cardioprotection against I/R injury also in aged diabetic patients.

Anti-angiogenic effect of exo-LncRNA TUG1 in myocardial infarction and modulation by remote ischemic conditioning

The successful use of exosomes in therapy after myocardial infarction depends on an improved understanding of their role in cardiac signaling and regulation. Here, we report that exosomes circulating after myocardial infarction (MI) carry LncRNA TUG1 which downregulates angiogenesis by disablement of the HIF-1α/VEGF-α axis and that this effect can be counterbalanced by remote ischemic conditioning (RIC). Rats with MI induced through left coronary artery ligation without (MI model) and with reperfusion (ischemia/reperfusion I/R model) were randomized to RIC, or MI (I/R) or sham-operated (SO) control. Data from one cohort study and one randomized-controlled trial of humans with MI were also utilized, the former involving patients who had not received percutaneous coronary intervention (PCI) and the latter patients with PCI. Exosome concentrations did not differ between intervention groups (RIC vs. control) in rats (MI and I/R model) as well as humans (with and without PCI). However, MI and I/R exosomes attenuated HIF-1α, VEGF-α, and endothelial function. LncRNA TUG1 was increased in MI and I/R exosomes, but decreased in SO and RIC exosomes. HIF-1α expression was downregulated with MI and I/R exosomes but increased with RIC exosomes. Exosome inhibition suppressed HIF-1α upregulation through RIC exosomes. VEGF-α was identified as HIF-1α-regulated target gene. Knockdown of HIF-1α decreased VEGF-α, endothelial cell capability, and tube formation. Overexpression of HIF-1α exerted opposite effects. Transfection and co-transfection of 293 T cells with exosome-inhibitor GW4869 and HIF-1α inhibitor si-HIF-1α confirmed the exosomal-LncRNA TUG1/HIF-1α/VEGF-α pathway. LncRNA TUG1 is a potential therapeutic target after MI with or without reperfusion through PCI.

A comprehensive and longitudinal cardiac magnetic resonance imaging study of the impact of coronary ischemia duration on myocardial damage in a highly translatable animal model

OBJECTIVES

We performed a comprehensive assessment of the effect of myocardial ischemia duration on cardiac structural and functional parameters by serial cardiac magnetic resonance (CMR) and characterized the evolving scar.

BACKGROUND

CMR follow-up on the cardiac impact of time of ischemia in a closed-chest animal model of myocardial infarction with human resemblance is missing.

METHODS

Pigs underwent MI induction by occlusion of the left anterior descending (LAD) coronary artery for 30, 60, 90 or 120 min and then revascularized. Serial CMR was performed on day 3 and day 42 post-MI. CMR measurements were also run in a sham-operated group. Cellular and molecular changes were investigated.

RESULTS

On day 3, cardiac damage and function were similar in sham and pigs subjected to 30 min of ischemia. Cardiac damage (oedema and necrosis) significantly increased from 60 min onwards. Microvascular obstruction was extensively seen in animals with ≥90 min of ischemia and correlated with cardiac damage. A drop in global systolic function and wall motion of the jeopardized segments was seen in pigs subjected to ≥60 min of ischemia. On day 42, scar size and cardiac dysfunction followed the same pattern in the animals subjected to ≥60 min of ischemia. Adverse left ventricular remodelling (worsening of both LV volumes) was only present in animals subjected to 120 min of ischemia. Cardiac fibrosis, myocyte hypertrophy and vessel rarefaction were similar in the infarcted myocardium of pigs subjected to ≥60 min of ischemia. No changes were observed in the remote myocardium.

CONCLUSION

Sixty-minute LAD coronary occlusion already induces cardiac structural and functional alterations with longer ischemic time (120 min) causing adverse LV remodelling.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their 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 comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Plasma exosomes generated by ischaemic preconditioning are cardioprotective in a rat heart failure model

BACKGROUND

Exosomes released into the plasma after brief cardiac ischaemia mediate subsequent cardioprotection. Whether donor exosomes can provide cardioprotection to recipients with chronic heart failure, which confers the highest perioperative risk, is unknown. We examined whether ischaemic preconditioning (IPC)-induced plasma exosomes exerted cardioprotection after their transfer from normal donors to post-infarcted failing hearts.

METHODS

Plasma exosomes were obtained from adult rats after IPC or sham. An exosome inhibitor GW4869 was administrated before IPC in an in vivo model of ischaemia/reperfusion (I/R) injury in normal rats. The IPC exosomes or control exosomes from normal donor rats were perfused to the normal or post-infarcted failing rat hearts before ischaemia in Langendorff perfusion experiments. Infarct size, cardiac enzymes, cardiac function, and pro-survival kinases were quantified.

RESULTS

The IPC stimulus increased the release of exosomes, whereas GW4869 inhibited the rise of plasma exosomes. Pre-treatment with GW4869 reversed IPC-mediated cardioprotection against in vivo I/R injury. In the Langendorff perfusion experiments, IPC exosomes from normal donor rats reduced mean infarct size from 41.05 (1.87)% to 31.43 (1.81)% and decreased lactate dehydrogenase activity in the post-infarcted failing rat hearts. IPC exosomes but not control exosomes activated pro-survival kinases in the heart tissues.

CONCLUSIONS

Ischaemic preconditioning-induced exosomes from normal rats can restore cardioprotection in heart failure after myocardial infarction, which is associated with activation of pro-survival protein kinases. These results suggest a potential perioperative therapeutic role for ischaemic preconditioning-induced exosomes.

Comparing CABG and PCI across the globe based on current regional registry evidence

There is an ongoing debate whether coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) provide better results for the treatment of coronary artery disease (CAD). We aimed to evaluate the impact of CABG or PCI on long-term survival based on local reports from different regions in the world. We systematically searched MEDLINE selecting studies that compared outcomes for CABG or PCI as a treatment for CAD in the last 10 years. Reports without all-cause mortality, multi-national cohorts, hybrid revascularization populations were excluded. Qualifying studies were statistically compared, and their geographic location visualized on a world map. From 5126 studies, one randomized and twenty-two observational studies (19 risk-adjusted) met the inclusion criteria. The mean follow-up was 4.7 ± 7 years and 18 different countries were included. In 17 studies, CABG was associated with better survival during follow-up, six studies showed no significant difference, and no study favored PCI. Periprocedural mortality was not different in seven, lower with PCI in one, lower with CABG in three and not reported in 12 studies. In regional registry-type comparisons, CABG is associated with better long-term survival compared to PCI in most regions of the world without evidence for higher periprocedural mortality.

Device-Based Approaches Targeting Cardioprotection in Myocardial Infarction: The Expanding Armamentarium of Innovative Strategies

Coronary reperfusion therapy has played a pivotal role for reducing mortality and heart failure after acute myocardial infarction. Although several adjunctive approaches have been studied for reducing infarct size further, both ischemia-reperfusion injury and microvascular obstruction are still major contributors to both early and late clinical events after acute myocardial infarction. The progress in the field of cardioprotection has found several promising proof-of-concept preclinical studies. However, translation from bench to bedside has not been very successful. This comprehensive review discusses the importance of infarct size as a driver of clinical outcomes post-acute myocardial infarction and summarizes recent novel device-based approaches for infarct size reduction. Device-based interventions including mechanical cardiac unloading, myocardial cooling, coronary sinus interventions, supersaturated oxygen therapy, and vagal stimulation are discussed. Many of these approaches can modify ischemic myocardial biology before reperfusion and offer unique opportunities to target ischemia-reperfusion injury.

Remote ischemic conditioning in Ossabaw minipigs induces the release of humoral cardioprotective triggers, but the myocardium does not respond with reduced infarct size

Ischemic preconditioning (IPC; brief cycles of coronary occlusion/reperfusion) is operative in all species tested so far and reduces infarct size through the release of trigger molecules and activation of signal transducer and activator of transcription (STAT)3 in pigs. We have recently demonstrated that IPC failed to protect Ossabaw minipigs, which had a genetic predisposition to, but not yet established a metabolic syndrome, from infarction and did not activate STAT3. We now subjected Ossabaw minipigs to remote ischemic conditioning (RIC; 4 × 5 min/5 min bilateral hindlimb ischemia-reperfusion) and analyzed the release of cardioprotective triggers into the circulation with the aim to distinguish whether IPC failed to stimulate trigger release or to activate intracellular signaling cascades upstream of STAT3. RIC or a placebo protocol, respectively, was induced in anesthetized pigs before 60 min/180 min coronary occlusion/reperfusion. Plasma, prepared from Ossabaw minipigs after RIC or placebo, was infused into isolated rat hearts subjected to 30 min/120 min global ischemia-reperfusion. In the Ossabaw minipigs, RIC did not reduce infarct size (49.5 ± 12.1 vs. 56.0 ± 11.8% of area at risk with placebo), and STAT3 was not activated. In isolated rat hearts, infusion of RIC plasma reduced infarct size (19.7 ± 6.7 vs. 33.2 ± 5.5% of ventricular mass with placebo) and activated STAT3. Pretreatment of rat hearts with the STAT3 inhibitor stattic abrogated such infarct size reduction and STAT3 activation. In conclusion, Ossabaw minipigs release cardioprotective triggers in response to RIC into the circulation, and lack of cardioprotection is attributed to myocardial nonresponsiveness.NEW & NOTEWORTHY Ischemic conditioning reduces myocardial infarct size in all species tested so far. In the present study, we used Ossabaw minipigs that had a genetic predisposition to, but not yet established a metabolic syndrome. In these pigs, remote ischemic conditioning (RIC) induced the release of cardioprotective triggers but did not reduce infarct size. Transfer of their plasma, however, reduced infarct size in isolated recipient rat hearts, along with signal transducer and activator of transcription (STAT)3 activation.

Influence of Short and Long Hyperglycemia on Cardioprotection by Remote Ischemic Preconditioning-A Translational Approach

The adverse impact of common diseases like diabetes mellitus and acute hyperglycemia on morbidity and mortality from myocardial infarction (MI) has been well documented over the past years of research. In the clinical setting, the relationship between blood glucose and mortality appears linear, with amplifying risk associated with increasing blood glucose levels. Further, this seems to be independent of a diagnosis of diabetes. In the experimental setting, various comorbidities seem to impact ischemic and pharmacological conditioning strategies, protecting the heart against ischemia and reperfusion injury. In this translational experimental approach from bedside to bench, we set out to determine whether acute and/or prolonged hyperglycemia have an influence on the protective effect of transferred human RIPC-plasma and, therefore, might obstruct translation into the clinical setting. Control and RIPC plasma of young healthy men were transferred to isolated hearts of young male Wistar rats in vitro. Plasma was administered before global ischemia under either short hyperglycemic (HGs Con, HGs RIPC) conditions, prolonged hyperglycemia (HGl Con, HGl RIPC), or under normoglycemia (Con, RIPC). Infarct sizes were determined by TTC staining. Control hearts showed an infarct size of 55 ± 7%. Preconditioning with transferred RIPC plasma under normoglycemia significantly reduced infarct size to 25 ± 4% (p < 0.05 vs. Con). Under acute hyperglycemia, control hearts showed an infarct size of 63 ± 5%. Applying RIPC plasma under short hyperglycemic conditions led to a significant infarct size reduction of 41 ± 4% (p < 0.05 vs. HGs Con). However, the cardioprotective effect of RIPC plasma under normoglycemia was significantly stronger compared with acute hyperglycemic conditions (RIPC vs. HGs RIPC; p < 0.05). Prolonged hyperglycemia (HGl RIPC) completely abolished the cardioprotective effect of RIPC plasma (infarct size 60 ± 7%; p < 0.05 vs. HGl Con; HGl Con 59 ± 5%).

Non-responsiveness to cardioprotection by ischaemic preconditioning in Ossabaw minipigs with genetic predisposition to, but without the phenotype of the metabolic syndrome

The translation of successful preclinical and clinical proof-of-concept studies on cardioprotection to the benefit of patients with reperfused acute myocardial infarction has been difficult so far. This difficulty has been attributed to confounders which patients with myocardial infarction typically have but experimental animals usually not have. The metabolic syndrome is a typical confounder. We hypothesised that there may also be a genuine non-responsiveness to cardioprotection and used Ossabaw minipigs which have the genetic predisposition to develop a diet-induced metabolic syndrome, but before they had developed the diseased phenotype. Using a prospective study design, a reperfused acute myocardial infarction was induced in 62 lean Ossabaw minipigs by 60 min coronary occlusion and 180 min reperfusion. Ischaemic preconditioning by 3 cycles of 5 min coronary occlusion and 10 min reperfusion was used as cardioprotective intervention. Ossabaw minipigs were stratified for their single nucleotide polymorphism as homozygous for valine (V/V) or isoleucine (I/I)) in the γ-subunit of adenosine monophosphate-activated protein kinase. Endpoints were infarct size and area of no-reflow. Infarct size (V/V: 54 ± 8, I/I: 54 ± 13% of area at risk, respectively) was not reduced by ischaemic preconditioning (V/V: 55 ± 11, I/I: 46 ± 11%) nor was the area of no-reflow (V/V: 57 ± 18, I/I: 49 ± 21 vs. V/V: 57 ± 21, I/I: 47 ± 21% of infarct size). Bioinformatic comparison of the Ossabaw genome to that of Sus scrofa and Göttingen minipigs identified differences in clusters of genes encoding mitochondrial and inflammatory proteins, including the janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway. The phosphorylation of STAT3 at early reperfusion was not increased by ischaemic preconditioning, different from the established STAT3 activation by cardioprotective interventions in other pig strains. Ossabaw pigs have not only the genetic predisposition to develop a metabolic syndrome but also are not amenable to cardioprotection by ischaemic preconditioning.

The protective effect of remote ischemic conditioning is lost in patients with hypercholesterolemia

Remote ischemic conditioning (RIC), brief repetitive cycles of ischemia and reperfusion in remote tissues, is known to induce robust protection against myocardial ischemia-reperfusion (I/R) injury in preclinical studies. However, translation of the beneficial effects to the clinical setting has been challenging. A possibility is that comorbidities, including hypercholesterolemia, interfere with the protective mechanisms of RIC. The aim of this study was to test if hypercholesterolemia attenuates the efficacy of RIC in patients with hypercholesterolemia. Patients with familial hypercholesterolemia (FH) with high (≥5.5 mmol/L) low-density lipoprotein cholesterol (LDL-C), FH with low (≤2.5 mmol/L) and healthy control subjects (n = 12 in each group) were included. Flow-mediated vasodilatation (FMD) of the brachial artery was evaluated, before and after a 20-min period of forearm ischemia and 20 min reperfusion (I/R) as a measure of endothelial function. Study subjects were randomized to a RIC protocol consisting of four cycles of 5 min of leg ischemia or sham using a crossover design. Forearm I/R induced significant reduction in FMD in all three groups during the sham procedure. RIC protected from endothelial dysfunction induced by forearm ischemia-reperfusion in healthy controls [FMD baseline 2.8 ± 2.3 vs. FMD after I/R + RIC 4.5 ± 4.0%; means (SD)] and in patients with FH with low LDL-C (4.5 ± 3.5 vs. 4.4 ± 4.2%). By contrast, RIC fails to protect against I/R-induced endothelial dysfunction in patients with FH and high LDL-C (3.9 ± 3.0 vs. 1.1 ± 1.5%; P < 0.01). These findings provide the first evidence in humans that the protective effect of RIC is lost in patients with elevated cholesterol.NEW & NOTEWORTHY We investigated the impact of hypercholesterolemia on the protective effect of RIC on ischemia-reperfusion injury in a well-characterized patient population with isolated hypercholesterolemia. The results show that the protective effect of RIC is absent in patients with hypercholesterolemia but is apparent in patients with hypercholesterolemic following treatment with lipid-lowering drugs. The results are of importance for the understanding of how comorbidities affect the therapeutic potential of RIC.

Volatile Anaesthesia versus Total Intravenous Anaesthesia for Cardiac Surgery—A Narrative Review

Recent research has contested the previously accepted paradigm that volatile anaesthetics improve outcomes in cardiac surgery patients when compared to intravenous anaesthesia. In this review we summarise the mechanisms of myocardial ischaemia/reperfusion injury and cardioprotection in cardiac surgery. In addition, we make a comprehensive analysis of evidence comparing outcomes in patients undergoing cardiac surgery under volatile or intravenous anaesthesia, in terms of mortality and morbidity (cardiac, neurological, renal, pulmonary).

Neuroprotective effect of remote ischemic preconditioning in patients undergoing cardiac surgery: A randomized controlled trial

Background

The neuroprotective effect of remote ischemic preconditioning (RIPC) in patients undergoing elective cardiopulmonary bypass (CPB)-assisted coronary artery bypass graft (CABG) or valvular cardiac surgery remains unclear.

Methods

A randomized, double-blind, placebo-controlled superior clinical trial was conducted in patients undergoing elective on-pump coronary artery bypass surgery or valve surgery. Before anesthesia induction, patients were randomly assigned to RIPC (three 5-min cycles of inflation and deflation of blood pressure cuff on the upper limb) or the control group. The primary endpoint was the changes in S-100 calcium-binding protein β (S100-β) levels at 6 h postoperatively. Secondary endpoints included changes in Neuron-specific enolase (NSE), Mini-mental State Examination (MMSE), and Montreal Cognitive Assessment (MoCA) levels.

Results

A total of 120 patients [mean age, 48.7 years; 36 women (34.3%)] were randomized at three cardiac surgery centers in China. One hundred and five patients were included in the modified intent-to-treat analysis (52 in the RIPC group and 53 in the control group). The primary result demonstrated that at 6 h after surgery, S100-β levels were lower in the RIPC group than in the control group (50.75; 95% confidence interval, 67.08 to 64.40 pg/ml vs. 70.48; 95% CI, 56.84 to 84.10 pg/ml, P = 0.036). Compared to the control group, the concentrations of S100-β at 24 h and 72 h and the concentration of NSE at 6 h, 24 h, and 72 h postoperatively were significantly lower in the RIPC group. However, neither the MMSE nor the MoCA revealed significant between-group differences in postoperative cognitive performance at 7 days, 3 months, and 6 months after surgery.

Conclusion

In patients undergoing CPB-assisted cardiac surgery, RIPC attenuated brain damage as indicated with the decreased release of brain damage biomarker S100-β and NSE.

Clinical trial registration

[ClinicalTrials.gov], identifier [NCT01231789].

Ischemia-Selective Cardioprotection by Malonate for Ischemia/Reperfusion Injury

BACKGROUND

Inhibiting SDH (succinate dehydrogenase), with the competitive inhibitor malonate, has shown promise in ameliorating ischemia/reperfusion injury. However, key for translation to the clinic is understanding the mechanism of malonate entry into cells to enable inhibition of SDH, its mitochondrial target, as malonate itself poorly permeates cellular membranes. The possibility of malonate selectively entering the at-risk heart tissue on reperfusion, however, remains unexplored.

METHODS

C57BL/6J mice, C2C12 and H9c2 myoblasts, and HeLa cells were used to elucidate the mechanism of selective malonate uptake into the ischemic heart upon reperfusion. Cells were treated with malonate while varying pH or together with transport inhibitors. Mouse hearts were either perfused ex vivo (Langendorff) or subjected to in vivo left anterior descending coronary artery ligation as models of ischemia/reperfusion injury. Succinate and malonate levels were assessed by liquid chromatography-tandem mass spectrometry LC-MS/MS, in vivo by mass spectrometry imaging, and infarct size by TTC (2,3,5-triphenyl-2H-tetrazolium chloride) staining.

RESULTS

Malonate was robustly protective against cardiac ischemia/reperfusion injury, but only if administered at reperfusion and not when infused before ischemia. The extent of malonate uptake into the heart was proportional to the duration of ischemia. Malonate entry into cardiomyocytes in vivo and in vitro was dramatically increased at the low pH (≈6.5) associated with ischemia. This increased uptake of malonate was blocked by selective inhibition of MCT1 (monocarboxylate transporter 1). Reperfusion of the ischemic heart region with malonate led to selective SDH inhibition in the at-risk region. Acid-formulation greatly enhances the cardioprotective potency of malonate.

CONCLUSIONS

Cardioprotection by malonate is dependent on its entry into cardiomyocytes. This is facilitated by the local decrease in pH that occurs during ischemia, leading to its selective uptake upon reperfusion into the at-risk tissue, via MCT1. Thus, malonate's preferential uptake in reperfused tissue means it is an at-risk tissue-selective drug that protects against cardiac ischemia/reperfusion injury.

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

Remote ischaemic conditioning: defining critical criteria for success-report from the 11th Hatter Cardiovascular Workshop

The Hatter Cardiovascular Institute biennial workshop, originally scheduled for April 2020 but postponed for 2 years due to the Covid pandemic, was organised to debate and discuss the future of Remote Ischaemic Conditioning (RIC). This evolved from the large multicentre CONDI-2-ERIC-PPCI outcome study which demonstrated no additional benefit when using RIC in the setting of ST-elevation myocardial infarction (STEMI). The workshop discussed how conditioning has led to a significant and fundamental understanding of the mechanisms preventing cell death following ischaemia and reperfusion, and the key target cyto-protective pathways recruited by protective interventions, such as RIC. However, the obvious need to translate this protection to the clinical setting has not materialised largely due to the disconnect between preclinical and clinical studies. Discussion points included how to adapt preclinical animal studies to mirror the patient presenting with an acute myocardial infarction, as well as how to refine patient selection in clinical studies to account for co-morbidities and ongoing therapy. These latter scenarios can modify cytoprotective signalling and need to be taken into account to allow for a more robust outcome when powered appropriately. The workshop also discussed the potential for RIC in other disease settings including ischaemic stroke, cardio-oncology and COVID-19. The workshop, therefore, put forward specific classifications which could help identify so-called responders vs. non-responders in both the preclinical and clinical settings.

Alpha-lipoic acid potentiates the anti-arrhythmic effects of ischemic postconditioning in the setting of cardiac ischemia/reperfusion injury in diabetic rats

Background

Prevention of lethal ventricular arrhythmias induced by myocardial ischemia/reperfusion (I/R) in diabetic patients is the major goal of cardioprotective strategies. Here, we aimed to examine the anti-arrhythmic effect of ischemic postconditioning (IPostC) and alpha-lipoic acid (ALA) in myocardial I/R injury of type-II diabetic rats, focusing on the involvement of connexin-43 and nitric oxide (NO) in this context.

Methods

Diabetes (duration of 12 weeks) was induced by high-fat diet and low dose of streptozotocin in thirty male Wistar rats (12 weeks old, 200-250 g). After mounting the hearts on the Langendorff apparatus, I/R was induced by the ligation of left anterior descending coronary artery for 35 min, and reperfusion for 60 min. ALA (100 mg/kg/day) was administered orally in diabetic rats for five weeks before I/R. IPostC was applied immediately at early reperfusion. The arrhythmias were evaluated according to the Lambeth convention. Connexin-43 expression and NO levels were assessed by western blotting and Griess calorimetric method, respectively.

Results

IPostC could not significantly decrease the number, duration, and incidence of premature ventricular contraction, ventricular tachycardia, and ventricular fibrillation, also the severity of arrhythmias in diabetic hearts. However, IPostC in combination with ALA-preconditioning significantly decreased the above mentioned parameters compared with untreated or monotherapies-received diabetic rats (P < 0.05 to P < 0.001). Furthermore, this combination therapy significantly increased connexin-43 expression and NO levels, compared with untreated diabetic rats (P < 0.01).

Conclusion

Preconditioning with ALA restored anti-arrhythmic effect of IPostC in diabetic hearts. Increased connexin-43 expression and NO levels may be the key players in this cardioprotection.

Aging, sex and NLRP3 inflammasome in cardiac ischaemic disease

Experimentally, many strong cardioprotective treatments have been identified in different animal models of acute ischaemia/reperfusion injury (IRI) and coronary artery disease (CAD). However, the translation of these cardioprotective therapies for the benefit of the patients into the clinical scenario has been very disappointing. The reasons for this lack are certainly multiple. Indeed, many confounding factors we must deal in clinical reality, such as aging, sex and inflammatory processes are neglected in many experiments. Due to the pivotal role of aging, sex and inflammation in determining cardiac ischaemic disease, in this review, we take into account age as a modifier of tolerance to IRI in the two sexes, dissecting aging and myocardial reperfusion injury mechanisms and the sex differences in tolerance to IRI. Then we focus on the role of the gut microbiota and the NLRP3 inflammasome in myocardial IRI and on the possibility to consider NLRP3 inflammasome as a potential target in the treatment of CAD in relationship with age and sex. Finally, we consider the cardioprotective mechanisms and cardioprotective treatments during aging in the two sexes.

Effects of ischemic conditioning on head and neck free flap oxygenation: a randomized controlled trial

Flap failure after microvascular reconstructive surgery is a rare but devastating complication caused by reperfusion injury and tissue hypoperfusion. Remote ischemic conditioning (RIC) provides protection against ischemia/reperfusion injury and reduces tissue infarction. We hypothesized that RIC would enhance flap oxygenation and exert organ-protective effects during head and neck free flap reconstructive surgery. Adult patients undergoing free flap transfer surgery for head and neck cancer were randomized to receive either RIC or sham-RIC during surgery. RIC consisted of four cycles of 5-min ischemia and 5-min reperfusion applied to the upper or lower extremity. The primary endpoint, tissue oxygen saturation of the flap, was measured by near-infrared spectroscopy on the first postoperative day. Organ-protective effects of RIC were evaluated with infarct size of rat hearts perfused with plasma dialysate from patients received RIC or sham-RIC. Between April 2018 and July 2019, 50 patients were randomized (each n = 25) and 46 were analyzed in the RIC (n = 23) or sham-RIC (n = 23) groups. Tissue oxygen saturation of the flap was similar between the groups (85 ± 12% vs 83 ± 9% in the RIC vs sham-RIC groups; P = 0.471). Myocardial infarct size after treatment of plasma dialysate was significantly reduced in the RIC group (44 ± 7% to 26 ± 6%; P = 0.018) compared to the sham-RIC group (42 ± 6% to 37 ± 7%; P = 0.388). RIC did not improve tissue oxygenation of the transferred free flap in head and neck cancer reconstructive surgery. However, there was evidence of organ-protective effects of RIC in experimental models.

Trial registration: Registry number of ClinicalTrials.gov: NCT03474952.

No sex-related differences in infarct size, no-reflow and protection by ischaemic preconditioning in Göttingen minipigs

Aims

Female sex has been proposed to be cardioprotective per se. Studies with myocardial ischaemia/reperfusion and infarct size as endpoint have demonstrated cardioprotection in female, castrated male and male pigs. These studies are difficult to compare, given the different pig strains, models, durations of ischaemia and methods of infarct size quantification. The few studies using both female and male pigs reported no differences in infarct size and cardioprotection. We therefore prospectively compared infarct size in Göttingen minipigs undergoing ischaemia/reperfusion (I/R) without and with ischaemic preconditioning (IPC) between female, castrated male and male pigs.

Methods and Results

In a prospective, randomised approach, 28 Göttingen open-chest, anaesthetised minipigs underwent 60 min ischaemia by distal left anterior descending artery (LAD) occlusion and 180 min reperfusion without and with IPC by 3 cycles of 5 min LAD occlusion/10 min reperfusion. Infarct size with I/R was not different between female, castrated male and male pigs (45±8 vs. 45±13 vs. 41±9% area at risk), as was the reduction in infarct size with IPC (25±11 vs. 30±8 vs. 19±10% area at risk). Also, the area of no-reflow was not different between female, castrated male and male pigs with I/R (57±13 vs. 35±7 vs. 47±26% infarct size) or IPC (4±10 vs.12±20 vs. 0±0% infarct size). Phosphorylation of signal transducer and activator of transcription 3 was increased at 10 min reperfusion by IPC but not by I/R to the same extent in female, castrated male and male pigs (198±30 vs. 230±165 vs. 179±107% of baseline).

Conclusion

Our data do not support the notion of sex- or castration-related differences in infarct size, coronary microvascular injury and cardioprotection by ischaemic preconditioning.

Translational perspective

The translation of successful preclinical studies on cardioprotection to the benefit of patients with reperfused myocardial infarction has been difficult. The difficulties have been attributed to confounders such as co-morbidities and co-medications which patients typically have but animals don´t, but also to age and sex. Notably, female sex has been considered as protective per se. We have now, using our established and clinically relevant pig model of reperfused acute myocardial infarction and ischaemic preconditioning as the most robust cardioprotective intervention looked for sex-related differences of infarct size, no-reflow and cardioprotection by ischaemic preconditioning in a prospectively powered approach but found none such difference.

Amelioration of endothelial dysfunction by sodium glucose co-transporter 2 inhibitors: pieces of the puzzle explaining their cardiovascular protection

Sodium glucose co‐transporter 2 inhibitors (SGLT‐2is) improve cardiovascular outcomes in both diabetic and non‐diabetic patients. Preclinical studies suggest that SGLT‐2is directly affect endothelial function in a glucose‐independent manner. The effects of SGLT‐2is include decreased oxidative stress and inflammatory reactions in endothelial cells. Furthermore, SGLT2is restore endothelium‐related vasodilation and regulate angiogenesis. The favourable cardiovascular effects of SGLT‐2is could be mediated via a number of pathways: (1) inhibition of the overactive sodium‐hydrogen exchanger; (2) decreased expression of nicotinamide adenine dinucleotide phosphate oxidases; (3) alleviation of mitochondrial injury; (4) suppression of inflammation‐related signalling pathways (e.g., by affecting NF‐κB); (5) modulation of glycolysis; and (6) recovery of impaired NO bioavailability. This review focuses on the most recent progress and existing gaps in preclinical investigations concerning the direct effects of SGLT‐2is on endothelial dysfunction and the mechanisms underlying such effects.

Cardioprotective Properties of Humoral Factors Released after Remote Ischemic Preconditioning in CABG Patients with Propofol-Free Anesthesia-A Translational Approach from Bedside to Bench

The cardioprotective effect of remote ischemic preconditioning (RIPC) is well detectable in experimental studies but not in clinical trials. Propofol, a commonly used sedative, is discussed to negatively influence the release of humoral factors after RIPC. Further, results from experimental and clinical trials suggest various comorbidities interact with inducible cardioprotective properties of RIPC. In the present study, we went back from bedside to bench to investigate, in male patients undergoing CABG surgery, whether (1) humoral factors are released after RIPC during propofol-free anesthesia and/or (2) DM interacts with plasma factor release. Blood samples were taken from male patients with and without DM undergoing CABG surgery before (control) and after RIPC (RIPC). To investigate the release of cardioprotective humoral factors into the plasma, isolated perfused hearts of young rats (n = 5 per group) were used as a bioassay. The hearts were perfused with patients’ plasma without (Con) and with RIPC (RIPC) for 10 min (1% of coronary flow) before global ischemia and reperfusion. In additional groups, the plasma of patients with DM was administered (Con DM, RIPC DM). Infarct size was determined by TTC staining. Propofol-free RIPC plasma of male patients without DM showed an infarct size of 59 ± 5% compared to 61 ± 13% with Con plasma (p = 0.973). Infarct sizes from patients with DM showed similar results (RIPC DM: 55 ± 3% vs. Con DM: 56 ± 4%; p = 0.995). The release of humoral factors into the blood after RIPC in patients receiving propofol-free anesthesia undergoing CABG surgery did not show any cardioprotective properties independent of a pre-existing diabetes mellitus.

Inhalational or total intravenous anesthetic for cardiac surgery: does the debate even exist?

PURPOSE OF REVIEW

Perioperative myocardial injury related to cardiac surgery is associated with organ dysfunction and increased mortality. Volatile anesthetics (VA) have been used during cardiac surgery for decades because of their direct and indirect preconditioning and protection against ischemia-reperfusion injury. The current review provides a summary of the latest literature comparing pharmacological preconditioning and the potential benefits of using VA versus total intravenous anesthesia (TIVA) for general anesthesia to improve outcomes after cardiac surgery.

RECENT FINDINGS

Recent literature reports lower mortality and better outcomes when VA is used alone or in combination with remote ischemic preconditioning compared with groups receiving TIVA. However, inconsistent research findings over the years have led to continued debate regarding the anesthetic technique considered more favorable for cardiac surgery.

SUMMARY

Research findings regarding the use of volatile anesthetic versus TIVA for better outcomes after cardiac surgery are inconsistent. Variability in timing, duration, dosing, and type of VA as well as surgical and patient-related factors may have influenced these results. Therefore, either technique can reasonably be adopted depending on provider and institutional preference and used safely in patients undergoing cardiac surgery.

Effects of late, repetitive remote ischaemic conditioning on myocardial strain in patients with acute myocardial infarction

Late, repetitive or chronic remote ischaemic conditioning (CRIC) is a potential cardioprotective strategy against adverse remodelling following ST-segment elevation myocardial infarction (STEMI). In the randomised Daily Remote Ischaemic Conditioning Following Acute Myocardial Infarction (DREAM) trial, CRIC following primary percutaneous coronary intervention (P-PCI) did not improve global left ventricular (LV) systolic function. A post-hoc analysis was performed to determine whether CRIC improved regional strain. All 73 patients completing the original trial were studied (38 receiving 4 weeks' daily CRIC, 35 controls receiving sham conditioning). Patients underwent cardiovascular magnetic resonance at baseline (5-7 days post-STEMI) and after 4 months, with assessment of LV systolic function, infarct size and strain (longitudinal/circumferential, in infarct-related and remote territories). At both timepoints, there were no significant between-group differences in global indices (LV ejection fraction, infarct size, longitudinal/circumferential strain). However, regional analysis revealed a significant improvement in longitudinal strain in the infarcted segments of the CRIC group (from - 16.2 ± 5.2 at baseline to - 18.7 ± 6.3 at follow up, p = 0.0006) but not in corresponding segments of the control group (from - 15.5 ± 4.0 to - 15.2 ± 4.7, p = 0.81; for change: - 2.5 ± 3.6 versus + 0.3 ± 5.6, respectively, p = 0.027). In remote territories, there was a lower increment in subendocardial circumferential strain in the CRIC group than in controls (- 1.2 ± 4.4 versus - 2.5 ± 4.0, p = 0.038). In summary, CRIC following P-PCI for STEMI is associated with improved longitudinal strain in infarct-related segments, and an attenuated increase in circumferential strain in remote segments. Further work is needed to establish whether these changes may translate into a reduced incidence of adverse remodelling and clinical events. Clinical Trial Registration: http://clinicaltrials.gov/show/NCT01664611 .

Negative interaction between nitrates and remote ischemic preconditioning in patients undergoing cardiac surgery: the ERIC-GTN and ERICCA studies

Remote ischaemic preconditioning (RIPC) using transient limb ischaemia failed to improve clinical outcomes following cardiac surgery and the reasons for this remain unclear. In the ERIC-GTN study, we evaluated whether concomitant nitrate therapy abrogated RIPC cardioprotection. We also undertook a post-hoc analysis of the ERICCA study, to investigate a potential negative interaction between RIPC and nitrates on clinical outcomes following cardiac surgery. In ERIC-GTN, 185 patients undergoing cardiac surgery were randomized to: (1) Control (no RIPC or nitrates); (2) RIPC alone; (3); Nitrates alone; and (4) RIPC + Nitrates. An intravenous infusion of nitrates (glyceryl trinitrate 1 mg/mL solution) was commenced on arrival at the operating theatre at a rate of 2-5 mL/h to maintain a mean arterial pressure between 60 and 70 mmHg and was stopped when the patient was taken off cardiopulmonary bypass. The primary endpoint was peri-operative myocardial injury (PMI) quantified by a 48-h area-under-the-curve high-sensitivity Troponin-T (48 h-AUC-hs-cTnT). In ERICCA, we analysed data for 1502 patients undergoing cardiac surgery to investigate for a potential negative interaction between RIPC and nitrates on clinical outcomes at 12-months. In ERIC-GTN, RIPC alone reduced 48 h-AUC-hs-cTnT by 37.1%, when compared to control (ratio of AUC 0.629 [95% CI 0.413-0.957], p = 0.031), and this cardioprotective effect was abrogated in the presence of nitrates. Treatment with nitrates alone did not reduce 48 h-AUC-hs-cTnT, when compared to control. In ERICCA there was a negative interaction between nitrate use and RIPC for all-cause and cardiovascular mortality at 12-months, and for risk of peri-operative myocardial infarction. RIPC alone reduced the risk of peri-operative myocardial infarction, compared to control, but no significant effect of RIPC was demonstrated for the other outcomes. When RIPC and nitrates were used together they had an adverse impact in patients undergoing cardiac surgery with the presence of nitrates abrogating RIPC-induced cardioprotection and increasing the risk of mortality at 12-months post-cardiac surgery in patients receiving RIPC.

Direct Ischemic Postconditioning After Carotid Endarterectomy in the Prevention of Postoperative Cerebral Ischemic Complications—Observational Case–Control Study

Introduction:

Ischemic postconditioning (IPCT) represents one of the several therapeutic strategies to attenuate ischemic reperfusion injury (IR) after carotid endarterectomy (CEA). We here present the first in-human study of IPCT in carotid surgery.

Methods:

The study represents an observational case-control study, with the data collected in our Institution carotid database. From December 2015 to December 2020, a total of 300 patients were included in our study; IPCT group consisted of 148 patients in whom ischemic postconditioning was performed while control group consisted of 152 patients in whom IPCT was not performed. Indications for IPCT technique were: severe unilateral internal carotid artery (ICA) stenosis (>90%), severe bilateral ICA stenosis (>80%), severe ICA stenosis (>80%) with contralateral ICA occlusion and ICA subocclusion. IPCT was performed by applying 6 cycles of 30 sec reperfusion (declamping of ICA)/30 sec ischemia (clamping of ICA) after finishing the procedure and initial declamping. Two groups of patients were compared in terms of occurrence of intrahospital and early postoperative stroke, TIA (transient ischemic attack) and neurologic morbidity.

Results:

Cumulative incidence of intrahospital postoperative stroke or TIA was significantly higher in the control group (5.3% vs 0.7%, P = .036). According to carotid plaque characteristics, patients in the IPCT group had significantly more frequent presence of heterogenous plaque, as well as ulcerated plaque, which was associated with the absence of postoperative stroke and significantly lower cumulative rate of TIA/stroke when compared to the control group (43.9% vs 8% and 47.3% vs 1.5%). During the follow-up period of 1 month after the surgery, there were no cases of stroke, TIA and deaths due to neurological causes in both groups of patients.

Conclusion:

Our results showed that IPCT significantly reduced the incidence of postoperative cerebral ischemic complications after CEA in high-risk patients for IR injury when compared to the control group.

Bioassays of Humoral Cardioprotective Factors Released by Remote Ischemic Conditioning in Patients Undergoing Coronary Artery Bypass Surgery

Remote ischemic conditioning (RIC) induces the release of circulating cardioprotective factors and attenuates myocardial ischemia/reperfusion injury. Evidence for such humoral cardioprotective factor(s) is derived from transfer with plasma (derivatives) from one individual undergoing RIC to another individual's heart, even across species. With transfer into an isolated perfused heart, only a single plasma (derivative) sample can be studied with infarct size as endpoint, and therefore the comparison of samples before and after RIC or between RIC and placebo is hampered by the inter-individual variation of infarct sizes in isolated perfused hearts. We therefore developed a preparation of cardiomyocytes from a single mouse heart, where aliquots of the same heart can undergo hypoxia/reoxygenation (H/R) with exposure to buffer, RIC, or placebo samples without or with pharmacological blockade. To validate this approach, we used plasma dialysates taken before and after RIC from patients undergoing coronary bypass grafting who had experienced protection by RIC (troponin release ↓ by 28% vs placebo). The cardiomyocyte bioassay had little variation after H/R with buffer (mean ± standard deviation; 7% ± 2% viable cells) and demonstrated preserved viability after RIC (15% ± 5% vs 6% ± 3% before). For comparison, infarct size in isolated mouse hearts after global ischemia and reperfusion was 22% ± 14% of left ventricular mass after versus 42% ± 14% before RIC. Stattic, an inhibitor of signal transducer and activator of transcription (STAT)3 protein, abrogated protection in the cardiomyocytes. We have thus established a cardiomyocyte bioassay to analyze RIC's protection which minimizes inter-individual variation and the use of animals.