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.

Laparoscopic ischemic conditioning of the stomach prior to esophagectomy induces gastric neo-angiogenesis

BACKGROUND

The risk of an anastomotic leakage (AL) following Ivor-Lewis esophagectomy is increased in patients with calcifications of the aorta or a stenosis of the celiac trunc. Ischemic conditioning (ISCON) of the gastric conduit prior to esophagectomy is supposed to improve gastric vascularization at the anastomotic site. The prospective ISCON trial was conducted to proof the safety and feasibility of this strategy with partial gastric devascularization 14 days before esophagectomy in esophageal cancer patients with a compromised vascular status. This work reports the results from a translational project of the ISCON trial aimed to investigate variables of neo-angiogenesis.

METHODS

Twenty esophageal cancer patients scheduled for esophagectomy were included in the ISCON trial. Serum samples (n = 11) were collected for measurement of biomarkers and biopsies (n = 12) of the gastric fundus were taken before and after ISCON of the gastric conduit. Serum samples were analyzed including 62 different cytokines. Vascularization of the gastric mucosa was assessed on paraffin-embedded sections stained against CD34 to detect the degree of microvascular density and vessel size.

RESULTS

Between November 2019 and January 2022 patients were included in the ISCON Trial. While serum samples showed no differences regarding cytokine levels before and after ISCON biopsies of the gastric mucosa demonstrated a significant increase in microvascular density after ISCON as compared to the corresponding gastric sample before the intervention.

CONCLUSION

The data prove that ISCON of the gastric conduit as esophageal substitute induces significant neo-angiogenesis in the gastric fundus which is considered as surrogate of an improved vascularization at the anastomotic site.

Effect of gastric ischemic conditioning prior to esophagectomy: systematic review and meta-analysis

Ischemia at the anastomotic site is thought to be a protagonist in the development of anastomosis-related complications while different strategies to overcome this problem have been reported. Gastric ischemic conditioning (GIC) prior to esophagectomy has been described with this intent. Evaluate the effect of GIC on anastomotic complications after esophagectomy. Scopus, Web of Science, MEDLINE, and PubMed were investigated up to March 31st, 2023. We considered articles that appraised short-term outcomes after GIC vs. no GIC in patients undergoing esophagectomy. Anastomotic leak (AL), anastomotic stricture (AS), and gastric conduit necrosis (GCN) were primary outcomes. Risk ratio (RR) and standardized mean difference (SMD) were used as pooled effect size measures, whereas 95% confidence intervals (95% CIs) were used to calculate related inference. Fourteen studies (1760 patients) were included. Of those, 732 (41.6%) underwent GIC, while 1028 (58.4%) underwent one-step esophagectomy. Compared with no GIC, GIC was related to a reduced RR for AL (R RR = 0.63; 95% CI 0.47-0.86; p < 0.01) and AS (RR = 0.51; 95% CI 0.29-0.91; p = 0.02), whereas no differences were found for GCN (RR = 0.56; 95% CI 0.19-1.61; p = 0.28). Postoperative pneumonia (RR = 1.09; p = 0.99), overall complications (RR = 0.87; p = 0.19), operative time (SMD - 0.58; p = 0.07), hospital stay (SMD 0.66; p = 0.09), and 30-day mortality (RR = 0.69; p = 0.22) were comparable. GIC prior to esophagectomy seems associated with a reduced risk for AL and AS. Further studies are necessary to identify the subset of patients who can benefit from this procedure, the optimal technique, and the timing of GIC prior to esophagectomy.

Ischemic Conditioning in the Right Colon and Terminal Ileum: An Experimental Rat Model

INTRODUCTION

Preoperative gastric ischemic conditioning (IC) improves the outcome of esophageal replacement gastroplasty and is associated with low morbidity. However, when the stomach cannot be used for esophageal replacement, a colonic replacement is required. The study aim was to assess the viability of right colon and terminal ileum IC in a rat model and the histological damage/recovery sequence and determine if neovascularization is a potential adaptive mechanism.

METHODS

The study was conducted in Rattus norvegicus with ileocolic vascular ligation. Seven groups of animals were established (6 rats per group) with groups defined by the date of their post-IC euthanasia (+1, +3, +6, +10, +15, and +21 days). Comparisons were made with a sham group. Viability of the model was defined as <10% of transmural necrosis. The evaluation of histological damage used the Chiu score in hematoxylin and eosin sections of paraffin-embedded specimens with CD31 immunohistochemical assessment of neovascularization by the median of submucosal vessel counts in 5 high-magnification fields.

RESULTS

Transmural colon necrosis occurred in 1/36 animals (2.78%) with no animal demonstrating transmural ileal necrosis. The maximum damage was observed in the colon on +1 day post-IC (average Chiu score 1.67, p = 0.015), whereas in the ileum, it was on days +1, +3, and +6 (average Chiu score 1.5, 1.3, and 1.17; p = 0.015, 0.002, and 0.015, respectively). In the +21-day group, histological recovery was complete in the colon in 4 (66.7%) of the 6 animals and in the ileum in 5 (83.3%) of 6 animals. There were no significant differences in quantitative neovascularization in any of the groups when compared with the sham group or when comparisons were made between groups.

CONCLUSIONS

The tested animal model for IC of the colon and terminal ileum appeared to be feasible. Histological damage was maximal between the 1st and 3rd day following IC, but by day 21, recovery was complete in two-thirds of the rats. There was no evidence in this preliminary IC model that would suggest neovascularization as an adaptive mechanism.

Translation of experimental cardioprotective capability of P2Y12 inhibitors into clinical outcome in patients with ST-elevation myocardial infarction

We studied the translational cardioprotective potential of P2Y₁₂ inhibitors against acute myocardial ischemia/reperfusion injury (IRI) in an animal model of acute myocardial infarction and in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). P2Y₁₂ inhibitors may have pleiotropic effects to induce cardioprotection against acute myocardial IRI beyond their inhibitory effects on platelet aggregation. We compared the cardioprotective effects of clopidogrel, prasugrel, and ticagrelor on infarct size in an in vivo rat model of acute myocardial IRI, and investigated the effects of the P2Y₁₂ inhibitors on enzymatic infarct size (48-h area-under-the-curve (AUC) troponin T release) and clinical outcomes in a retrospective study of STEMI patients from the CONDI-2/ERIC-PPCI trial using propensity score analyses. Loading with ticagrelor in rats reduced infarct size after acute myocardial IRI compared to controls (37 ± 11% vs 52 ± 8%, p < 0.01), whereas clopidogrel and prasugrel did not (50 ± 11%, p > 0.99 and 49 ± 9%, p > 0.99, respectively). Correspondingly, troponin release was reduced in STEMI patients treated with ticagrelor compared to clopidogrel (adjusted 48-h AUC ratio: 0.67, 95% CI 0.47-0.94). Compared to clopidogrel, the composite endpoint of cardiac death or hospitalization for heart failure within 12 months was reduced in STEMI patients loaded with ticagrelor (HR 0.63; 95% CI 0.42-0.94) but not prasugrel (HR 0.84, 95% CI 0.43-1.63), prior to PPCI. Major adverse cardiovascular events did not differ between clopidogrel, ticagrelor, or prasugrel. The cardioprotective effects of ticagrelor in reducing infarct size may contribute to the clinical benefit observed in STEMI patients undergoing PPCI.

Cardioprotection by post-conditioning with exogenous triiodothyronine in isolated perfused rat hearts and isolated adult rat cardiomyocytes

Ischemic post-conditioning (iPoCo) by coronary re-occlusion/reperfusion during immediate reperfusion after prolonged myocardial ischemia reduces infarct size. Mechanical manipulation of culprit lesions, however, carries the risk of coronary microembolization which may obscure iPoCo's cardioprotection. Pharmacological post-conditioning with exogenous triiodothyronine (T3) could serve as an alternative conditioning strategy. Similar to iPoCo, T3 may activate cardioprotective prosurvival pathways. We aimed to study T3's impact on infarct size and its underlying signal transduction. Hearts were isolated from male Lewis rats (200-380 g), buffer-perfused and subjected to 30 min/120 min global zero-flow ischemia/reperfusion (I/R). In additional hearts, either iPoCo (2 × 30 s/30 s I/R) was performed or T3 (100-500 µg/L) infused at reperfusion. Infarct size was demarcated with triphenyl tetrazolium chloride staining and calculated as percent of ventricular mass. Infarct size was reduced with iPoCo to 16 ± 7% vs. 36 ± 4% with I/R only. The maximum infarct size reduction was observed with 300 µg/L T3 (14 ± 2%). T3 increased the phosphorylation of protein kinase B and mitogen extracellular-regulated-kinase 1/2, both key enzymes of the reperfusion injury salvage kinase (RISK) pathway. Pharmacological RISK blockade (RISK-BL) during reperfusion abrogated T3's cardioprotection (35 ± 10%). Adult ventricular cardiomyocytes were isolated from buffer-perfused rat hearts and exposed to 30 min/5 min hypoxia/reoxygenation (H/R); reoxygenation was initiated without or with T3, respectively, and without or with RISK-BL, respectively. Maximal preservation of viability was observed with 500 µg/L T3 after H/R (27 ± 4% of all cells vs. 5 ± 3% in time-matched controls). Again, RISK-BL abrogated protection (11 ± 3%). Mitochondria were isolated at early reperfusion from buffer-perfused rat hearts without or with iPoCo or 300 µg/L T3, respectively, at reperfusion. T3 improved mitochondrial function (i.e.: increased respiration, adenosine triphosphate production, calcium retention capacity, and decreased reactive oxygen species formation) to a similar extent as iPoCo. T3 at reperfusion reduces infarct size by activation of the RISK pathway. T3's protection is a cardiomyocyte phenomenon and targets mitochondria.

Mini Review (Part I): An Experimental Concept on Exercise and Ischemic Conditioning in Stroke Rehabilitation

Stroke remains a leading cause of adult death and disability. Poststroke rehabilitation is vital for reducing the long-term sequelae of brain ischemia. Recently, physical exercise training has been well established as an effective rehabilitation tool, but its efficacy depends on exercise parameters and the patient's capacities, which are often altered following a major cerebrovascular event. Thus, ischemic conditioning as a rehabilitation intervention was considered an “exercise equivalent,” but the investigation is still in its relative infancy. In this mini-review, we discuss the potential for physical exercise or ischemic conditioning and its relation to angiogenesis, neurogenesis, and plasticity in stroke rehabilitation. This allows the readers to understand the context of the research and the application of ischemic conditioning in poststroke rehabilitation.

Sex differences in fatigability after ischemic preconditioning of non-exercising limbs

Background

Ischemic preconditioning (IPC) is suggested to decrease fatigability in some individuals but not others. Sex differences in response to IPC may account for this variability and few studies systematically investigated the effects of IPC in men and women. The goal of this study was to determine if time to task failure, perception of pain, and neuromuscular mechanisms of fatigability were altered by IPC in men and women.

Methods

Ten women (29 ± 5 years old) and 10 men (28 ± 6 years old) performed isometric contractions with the plantar flexor muscles of the dominant leg at 20% of maximal voluntary contraction until task failure. We used a repeated measures design where each individual performed 3 randomized and counterbalanced test sessions: (A) IPC session, cuff inflation and deflation (5 min each repeated 3 times) performed before the exercise by inflating cuffs to the non-dominant leg and arm; (B) sham session, cuffs were inflated for a short period (1 min); and (C) control session, no cuffs were involved.

Results

Compared with control, IPC increased time to task failure in men (mean difference, 5 min; confidence interval (CI) of mean difference, 2.2; 7.8 min; P = 0.01) but not women (mean difference, − 0.6 min; CI of mean difference, − 3.5; 2.4 min; P = 0.51). In men, but not women, the IPC-induced increase in time to task failure was associated with lower response to pressure pain (r = − 0.79). IPC further exposed sex differences in arterial pressure during fatiguing contractions (session × sex: P < 0.05). Voluntary activation, estimated with the twitch interpolation technique, and presynaptic inhibition of leg Ia afferents were not altered after IPC for men and women. The tested variables were not altered with sham.

Conclusions

The ergogenic effect of IPC on time to task failure was observed only in men and it was associated with reductions in the perception of pain. This pilot data suggest the previously reported inter-individual variability in exercise-induced fatigability after IPC could be a consequence of the sex and individual response to pain.

Effects of Hypoxic and Ischemic Clinical Conditions on the Outcomes of Acute Ischemic Stroke Patients

Background

Several studies have shown the neuroprotective role afforded by hypoxic and ischemic preconditioning in cerebrovascular disorders. There are several clinical conditions which simulate the hypoxic and ischemic conditioning in humans. The aim of this retrospective study is to identify whether the presence of any clinical scenarios mimicking the hypoxic and ischemic conditions prior to the current acute ischemic stroke (AIS) has a neuroprotective role in these patients.

Materials and methods

Data were collected for patients >18 years of age who underwent endovascular treatment for AIS from January 2009 to June 2015. A good outcome was defined as modified Rankin score (mRS) of 0 to 3 at discharge and a poor outcome as mRS of 4-6. A logistic regression analysis was performed to identify independent predictors of outcomes at discharge in both groups. A p value of <0.05 was considered statistically significant for all analyses.

Results

A total of 102 patients, aged 67 ± 16 years with median preprocedural National Institute of Health Stroke Scale (NIHSS) score 17.5 (1-36), were included. Twenty-one (21%) patients had a good outcome (mRS: 0-3) and 81 (79%) had a poor outcome (mRS: 4-6). A logistic regression analysis identified higher NIHSS score [odds ratio (OR): 1.251, confidence interval (CI): 1.11-1.40, p = 0.0002] and history of transient ischemic attack (TIA; OR: 7.881, CI: 1.05-21.01, p < 0.04) as predictors of a poor outcome at discharge.

Conclusion

Our data suggest that the occurrence of TIA preceding an AIS may be associated with the poor outcomes in patients with AIS, although this finding needs confirmation in larger studies.

How to cite this article

Athiraman U, Tempelhoff R, Karanikolas M. Effects of Hypoxic and Ischemic Clinical Conditions on the Outcomes of Acute Ischemic Stroke Patients. Indian J Crit Care Med 2020;24(2):104-108.

Two-stage hybrid Ivor-Lewis esophagectomy as surgical strategy to reduce postoperative morbidity for high-risk patients

BACKGROUND

Ivor-Lewis esophagectomy (ILE) is the standard surgical care for esophageal cancer patients but postoperative morbidity impairs quality of life and reduces long-term oncological outcome. Two-stage ILE separating the abdominal and thoracic phase into two distinct surgical procedures has proven to enhance microcirculation of the gastric conduit and therefore most likely reduces complications. However, two-stage ILE has not been evaluated systematically in selected groups of patients scheduled for this procedure. This investigation aims to demonstrate the feasibility of two-stage ILE in high-risk patients.

PATIENTS AND METHODS

In this retrospective analysis of data obtained from a prospective database, a consecutive series of 275 hybrid ILE (hILE) were included. Patients were divided into two groups based on one- or two-stage hILE. Postoperative complications were assessed according to ECCG (Esophageal Complication Consensus Group) criteria and compared using the Clavien-Dindo score. Indication for two-stage esophagectomy was classified as pre- or intraoperative decision.

RESULTS

34 out of 275 patients (12.7%) underwent two-stage hILE. Patients of the two-stage group were significantly older. In 21 of 34 patients (61.8%) the decision for a two-stage procedure was made prior to esophagectomy, in 13 (38.2%) patients intraoperatively after completion of the laparoscopic gastric mobilization. The most frequent preoperative reason to select the two-stage procedure was a stenosis of the coeliac trunc and superior mesenteric artery (n = 10). The predominant cause for an intraoperative change of strategy was a laparoscopically diagnosed hepatic fibrosis/cirrhosis (n = 5).Overall morbidity and major' complications (CD > IIIa) were comparable for both groups (11.7% in both groups). The overall anastomotic leak rate was 12.4% and was non-significant lower for the two-stage procedure.

CONCLUSION

Two-stage hILE is a feasible concept to individualize the surgical treatment of patients with well-defined clinical risk factors for postoperative morbidity. It can also be applied after completion of the abdominal phase of IL esophagectomy without compromising the patient safety.

Remote ischemic conditioning improves outcome independent of anesthetic effects following shockwave-induced traumatic brain injury

Traumatic brain injury due to primary blast exposure is a major cause of ongoing neurological and psychological impairment in soldiers and civilians. Animal and human evidence suggests that low-level blast exposure is capable of inducing white matter injury and behavioural deficits. There are currently no effective therapies to treat the underlying suspected pathophysiology of low-level primary blast or concussion. Remote ischemic conditioning (RIC) has been shown to have cardiac, renal and neuro-protective effects in response to brief cycles of ischemia. Here we examined the effects of RIC in two models of blast injury. We used a model of low-level primary blast in rats to evaluate the effects of RIC neurofilament expression. We subsequently used a model of traumatic brain injury in adult zebrafish using pulsed high intensity focused ultrasound (pHIFU) to evaluate the effects of RIC on behavioural outcome and apoptosis in a post-traumatic setting. In blast exposed rats, RIC pretreatment modulated NF200 expression suggesting an innate biological buffering effect. In zebrafish, behavioural deficits and apoptosis due to pHIFU-induced brain injury were reduced following administration of serum derived from RIC rats. The results in the zebrafish model demonstrate the humoral effects of RIC independent of anesthetic effects that were observed in the rat model of injury. Our results indicate that RIC is effective in improving outcome following modeled brain trauma in pre- and post-injury paradigms. The results suggest a potential role for innate biological systems in the protection against pathophysiological processes associated with impairment following shockwave induced trauma.

Remote ischemic conditioning improves cognition in patients with subcortical ischemic vascular dementia

BACKGROUND

Subcortical ischemic vascular dementia (SIVD) is very common among the older people, but has no approved treatment. Preclinical trials show that remote ischemic conditioning (RIC) reduces recurrence of ischemic stroke. We hypothesize that RIC may also be an effective therapy for patients with SIVD.

METHODS

Thirty-seven consecutive SIVD cases were enrolled in this randomized control study. Eighteen RIC patients underwent five brief cycles of conditioning (bilateral upper limb compression at 200 mmHg) followed by reperfusion twice daily over 6 consecutive months. Nineteen control patients underwent the same process, but at a pressure of 60 mmHg which caused no restriction on the blood flow of the upper limb. The primary outcome measures were changes in neuropsychological assessments. The secondary outcomes included the changes in high-sensitive C-reactive protein (hs-CRP) concentration, white matter lesion volume (WMLV), diffusion tension imaging (DTI) metrics of white matter. All data were collected at baseline and follow-up.

RESULTS

A significant treatment difference favoring RIC at 6 months was observed on performance of Hopkins Verbal Learning Test-Revised (HVLT-R), Controlled Oral Word Association Test (COWAT), Trail Making Test A and B (TMT-A & TMT-B), and Judgment of Line Orientation (JLO) (p < 0.05). The control group did not show much improvement after the treatment, and only with a slight change in HVLT-R and TMT-R (p < 0.05). Covariance analysis of efficacy between the two groups suggested that RIC patients performed better on JLO than control patients at the 6-month follow-up (RIC 23.10 vs. control 18.56; p = 0.013). Although DTI metrics were comparable, Hs-CRP levels and WMLV in RIC patients showed a declining trend.

CONCLUSIONS

Over the 6-month treatment period, we found that RIC was safe and effective for improving cognitive function in SIVD patients.

TRIAL REGISTRATION

Clinical Trial Registration ( http://www.clinicaltrials.gov ), Unique identifier: NCT03022149; Retrospectively registered; Date of registration: January 16, 2017.

Central Noradrenergic Agonists in the Treatment of Ischemic Stroke-an Overview

Ischemic stroke is the leading cause of morbidity and mortality with a significant health burden worldwide and few treatment options. Among the short- and long-term effects of ischemic stroke is the cardiovascular sympathetic autonomic dysfunction, presented in part as the by-product of the ischemic damage to the noradrenergic centers of the brain. Unlike high levels in the plasma, the brain may face suboptimal levels of norepinephrine (NE), with adverse effects on the clinical and functional outcomes of ischemic stroke. The intravenous administration of NE and other sympathomimetic agents, in an attempt to increase cerebral perfusion pressure, often aggravates the ischemia-induced rise in blood pressure (BP) with life-threatening consequences for stroke patients, the majority of whom present with hypertension at the time of admission. Unlike the systemic administration, the central administration of NE reduces BP while exerting anti-inflammatory and neuroprotective effects. These characteristics of centrally administered NE, combined with the short latency of response, make it an ideal candidate for use in the acute phase of stroke, followed by the use of centrally acting noradrenergic agonists, such as NE reuptake inhibitors and B2-adrenergic receptor agonists for stroke rehabilitation. In addition, a number of nonpharmacological strategies, such as transcutaneous vagus nerve stimulation (tVNS) and trigeminal nerve stimulation (TNS), have the potential to enhance the central noradrenergic functional activities and improve stroke clinical outcomes. Many factors could influence the efficacy of the noradrenergic treatment in stroke patients. These factors include the type of the noradrenergic agent; the dose, frequency, and duration of administration; the timing of administration in relation to the acute event; and the site and characteristics of the ischemic lesions. Having this knowledge, combined with the better understanding of the regulation of noradrenergic receptors in different parts of the brain, would pave the path for the successful use of the centrally acting noradrenergic agents in the management of ischemic stroke.

Attenuation of ST-segment elevation after ischemic conditioning maneuvers reflects cardioprotection online

Ischemic conditioning maneuvers, when induced either locally in the heart or remotely from the heart, reduce infarct size. However, infarct size reduction can be assessed no earlier than hours after established reperfusion. ST-segment elevation and its attenuation might reflect cardioprotection by ischemic conditioning online. Pigs were subjected to regional myocardial ischemia/reperfusion (1 h/3 h). Ischemic conditioning was induced prior to ischemia either locally (preconditioning; IPC; n = 15) or remotely (remote preconditioning; RIPC; n = 21), remotely during ischemia (remote perconditioning; RPER; n = 18), or locally at reperfusion (postconditioning; POCO; n = 9). Pigs without conditioning served as controls (PLA; n = 29). Area at risk and infarct size were measured postmortem, and ST-segment elevation was analyzed in a V2-like electrocardiogram lead. Ischemic conditioning reduced infarct size (PLA 42 ± 11% of area at risk; IPC 18 ± 10%; RIPC 22 ± 12%; RPER 23 ± 12%, POCO 22 ± 11%). With PLA, ST-segment elevation was increased at 5 min ischemia, sustained until 55 min ischemia and further increased at 10 min reperfusion. IPC and RIPC did not impact on ST-segment elevation at 5 min ischemia, but attenuated ST-segment elevation at 55 min ischemia. With RPER, ST-segment elevation was not different from that with PLA at 5 min, but attenuated at 55 min ischemia. POCO abolished the further increase of ST-segment elevation with reperfusion. Cardioprotection by ischemic conditioning is robustly reflected by attenuation of ST-segment elevation online.

Dose of remote limb ischemic conditioning for enhancing learning in healthy young adults

Remote limb ischemic conditioning (RLIC) is a technique in which tissues distant from the target organ are exposed to brief, sub-lethal bouts of ischemia. The effects of remotely applied ischemic conditioning are systemically transferred to the target organ, and typically manifested as protection from subsequent ischemic injury. Previous studies in our lab have found and confirmed that RLIC enhances learning and retention during motor training on a balance task. The current study tested the effect of RLIC dose (number of cycles) on learning enhancement in young, healthy adults. Forty healthy participants age 18-40 years were randomized to receive 5 cycles of sham conditioning (n = 9), 3 cycles of RLIC (n = 11), 4 cycles of RLIC (n = 10), or 5 cycles of RLIC (n = 10) using a blood pressure cuff around the upper arm once a day for 7 consecutive weekdays (Days 1-7). Participants concurrently trained on a balance task, bimanual cup stacking task, and a discrete sequence production task on Days 3-7. Change in performance on each of the three tasks was compared across groups. Participants in all four groups improved their performance on each of the three tasks over time. However, RLIC at any dose did not enhance learning on any of the three tasks. While RLIC is safe, inexpensive, and clinically feasible, reproducibility may be challenged by unidentified factors, raising critical challenges to the straightforward translation of RLIC for improving rehabilitation outcomes in individuals recovering from neurological injury.

The effect of repeated remote ischemic postconditioning on infarct size in patients with an ischemic stroke (REPOST): study protocol for a randomized clinical trial

Background

Remote ischemic postconditioning (rIPostC) refers to the observation that repeated, short periods of ischemia protect remote areas against tissue damage during and after prolonged ischemia. Based on previous observations of a potential neuroprotective effect of rIPostC, the aim of this study is to evaluate whether repeated rIPostC after an ischemic stroke can reduce infarct size, which could be translated to an improvement in clinical outcomes.

Methods/design

We will enroll 200 ischemic stroke patients to daily rIPostC or sham conditioning during hospitalization into a randomized single-blind placebo-controlled trial. The intervention consists of twice daily exposure to four cycles of 5-min cuff inflation around the upper arm to > 20 mmHg above systolic blood pressure (i.e., rIPostC) or 50 mmHg (i.e., control), followed by 5 minutes of deflation. The primary outcome is infarct size, measured using an MRI diffusion-weighted image at the end of hospitalization. Secondary outcomes include the Modified Rankin Scale, National Institutes of Health Stroke Scale, quality of life, and cardiovascular and cerebrovascular morbidity and mortality. To explore possible underlying mechanisms of rIPostC, venous blood will be sampled to assess biomarkers of inflammation and vascular health.

Discussion

Previous studies in animals and humans, using a single bout of remote ischemic conditioning, report a potential effect of rIPostC in attenuating neural damage. Although repeated rIPostC has been investigated for cardiovascular disease patients and preclinical stroke models, no previous study has explored the potential physiological and clinical effects of repeatedly applying rIPostC during the hospitalization phase after a stroke.

Trial registration

Netherlands Trial Register, NTR6880. Registered on 8 December 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3264-0) contains supplementary material, which is available to authorized users.

Feasibility of prehospital delivery of remote ischemic conditioning by emergency medical services in chest pain patients: protocol for a pilot study

Background

Remote ischemic conditioning (RIC) is a non-invasive procedure with hypothesized therapeutic benefits for patients experiencing an acute ST-elevation myocardial infarction (STEMI). Further study of emergency medical services (EMS) delivery of RIC in the prehospital setting is needed to inform the design and methods for future clinical trials of RIC in STEMI patients. The main objective of this pilot study is to assess the feasibility of prehospital delivery of RIC by EMS providers in the United States.

Methods

We will conduct a single-arm study of the standard RIC procedure (i.e., up to 4 cycles of alternating 5-min inflation and 5-min deflation of an upper arm cuff) administered by EMS paramedics in 50 patients experiencing acute onset chest pain. The investigational autoRIC® device (CellAegis Devices, Inc., Toronto, Ontario) will be initiated by paramedics during ground ambulance transport. Automated RIC cycles will continue through emergency department arrival and stay. The primary endpoint will be the completion of all 4 cycles of RIC without interruption. We will also examine study procedures and collect qualitative data from study participants and paramedics.

Discussion

To our knowledge, this will be the first study in the United States to assess the feasibility of completing the 40-min RIC procedure when initiated during ground ambulance transport. Findings from this pilot study will be used to optimize the design and methods for a future efficacy trial of RIC in acute STEMI patients.

Trial registration

NCT03400579 (ClinicalTrials.gov). Registered on 17 January 2018.

Remote ischemic conditioning during primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction: a systematic review and meta-analysis

Objective

This systematic review was designed to evaluate the efficacy of remote ischemic conditioning (RIC) with primary percutaneous coronary intervention (PCI) versus primary PCI alone for ST-segment elevation myocardial infarction (STEMI).

Search strategy

Computerized search for trials from PubMed, EMBASE, CENTRAL and Cochrane Database of Systematic Reviews databases.

Selection criteria

Trials investigating RIC plus primary PCI (group A) versus primary PCI alone (group B).

Outcome measures

Myocardial enzyme levels; left ventricular ejection fraction (LVEF); major adverse cardiac and cerebrovascular events (MACCEs); TIMI flow grade III; myocardial salvage index or infarct size per patients.

Results

In all, 14 studies involving 3165 subjects were included. There was a significant association of myocardial edema levels, myocardial salvage index and incidence of MACCEs in group A compared with group B (myocardial edema levels: SMD = − 0.36, 95% CI (− 0.59, − 0.13); myocardial salvage index: MD = 0.06, 95% CI (0.02, 0.10); MACCE: OR = 0.70, 95% CI (0.57, 0.85)). With regard to infarct size, TIMI flow grade III and LVEF, group A appeared to be equivalent with group B (infarct size: MD = − 1.67, 95% CI (− 3.46, 0.11); TIMI flow grade III: OR = 1.04, 95% CI (0.71, 1.52); LVEF: MD = 0.74, 95% CI (− 0.80, 2.28)).

Conclusion

RIC was associated with lower myocardial edema levels, myocardial salvage index and incidence of MACCE, while non-significant beneficial effect on infarct size, TIMI flow grade III or LVEF. These findings suggest that RIC is a promising adjunctive treatment to PCI for the prevention of reperfusion injury in STEMI patients.

Reperfusion Changes After Stroke and Practical Approaches for Neuroprotection

Reperfusion is the first line of care in a growing number of eligible acute ischemic stroke patients. Early reperfusion with thrombolytic drugs and endovascular mechanical devices is associated with improved outcome and lower mortality rates compared with natural history. Reperfusion is not without risk, however, and may result in reperfusion injury, which manifests in hemorrhagic transformation, brain edema, infarct progression, and neurologic worsening. In this article, the functional and structural changes and underlying molecular mechanisms of ischemia and reperfusion are reviewed. The pathways that lead to reperfusion injury and novel neuroprotective strategies with endogenous properties are discussed.

Intracranial atherosclerotic disease

Intracranial atherosclerosis (ICAS) is a progressive pathological process that causes progressive stenosis and cerebral hypoperfusion and is a major cause of stroke occurrence and recurrence around the world. Multiple factors contribute to the development of ICAS. Angiography imaging techniques can improve the diagnosis of and the selection of appropriate treatment regimens for ICAS. Neither aggressive medication nor endovascular interventions can eradicate stroke recurrence in patients with ICAS. Non-pharmacological therapies such as remote ischemic conditioning and hypothermia are emerging. Comprehensive therapy with medication in combination with endovascular intervention and/or non-pharmacological treatment may be a potential strategy for ICAS treatment in the future. We summarized the epidemiology, pathophysiological mechanisms, risk factors, biomarkers, imaging and management of ICAS.

Gastric Ischemic Conditioning Prior to Esophagectomy Is Associated with Decreased Stricture Rate and Overall Anastomotic Complications

BACKGROUND

Gastric ischemic conditioning prior to esophagectomy can increase neovascularization of the new conduit. Prior studies of ischemic conditioning have only investigated reductions in anastomotic leaks. Our aim was to analyze the association between gastric conditioning and all anastomotic outcomes as well as overall morbidity in our cohort of esophagectomy patients.

METHODS

We performed a retrospective review of patients undergoing esophagectomy from 2010 to 2015 in a National Cancer Institute designated center. Ischemic conditioning (IC) was performed on morbidly obese patients, those with cardiovascular disease or uncontrolled diabetes, and those requiring feeding jejunostomy and active tobacco users. IC consisted of transection of the short gastric vessels and ligation of the left gastric vessels. Primary outcomes consisted of all postoperative anastomotic complications. Secondary outcomes were overall morbidity.

RESULTS

Two-hundred and seven esophagectomies were performed with an average follow-up of 19 months. Thirty-eight patients (18.4%) underwent conditioning (IC). This group was similar to patients not conditioned (NIC) in age, preoperative pathology, and surgical approach. Five patients in the ischemic conditioning group (13.2%) and 57 patients (33.7%) in the NIC experienced anastomotic complications (p = 0.011). Ischemic conditioning significantly reduced the postoperative stricture rate fourfold (5.3 vs. 20.7% p = 0.02). IC patients experienced significantly fewer complications overall (36.8 vs. 56.2% p = 0.03).

CONCLUSIONS

Gastric ischemic conditioning is associated with fewer overall anastomotic complications, fewer strictures, and less morbidity. Randomized studies may determine optimal selection criteria to determine whom best benefits from ischemic conditioning.

Current Modalities and Mechanisms Underlying Cardioprotection by Ischemic Conditioning

Ischemic preconditioning is a process which serves to mitigate reperfusion injury. Preconditioning of the heart can be achieved through natural, pharmacological, and mechanical means. Mechanical preconditioning appears to have the greatest chance of good outcomes while methods employing pharmacologic preconditioning have been largely unsuccessful. Remote ischemic preconditioning achieves a cardioprotective effect by applying cycles of ischemia and reperfusion in a distal limb, stimulating the release of a neurohumoral cardioprotective factor incited by stimulation of afferent neurons. The cardioprotective factor stimulates the reperfusion injury salvage kinase (RISK) and survivor activator factor enhancement (SAFE) signaling cascades in cardiomyocytes which promote cell survival by the expression of anti-apoptotic genes and inhibition of the opening of mitochondrial permeability transition pores. Clinical application of ischemic preconditioning involving targets in the RISK and SAFE signaling appears promising in the treatment of acute myocardial infarction; however, clinical trials have yet to demonstrate additional benefit to current therapy.

Reperfusing the myocardium - a damocles Sword

Return of blood flow after periodic ischemia is often accompanied by myocardial injury, commonly known as lethal reperfusion injury (RI). Experimental studies have shown that 50% of muscle die of ischemia and another 50% die because of reperfusion. It is characterized by myocardial, vascular, or electrophysiological dysfunction that is induced by the restoration of blood flow to previously ischemic tissue. This phenomenon reduces the efficiency of the present modalities used to combat the ischemic myocardium. Moreover, despite an improved understanding of the pathophysiology of this process and encouraging preclinical trials of multiple agents, most of the clinical trials to prevent RI have been disappointing and leaves us at ground zero to explore newer approaches.

Remote tissue conditioning - An emerging approach for inducing body-wide protection against diseases of ageing

We have long accepted that exercise is 'good for us'; that - put more rigorously - moderate exercise is associated with not just aerobic fitness but also reduced morbidity and reduced mortality from cardiovascular disease and even malignancies. Caloric restriction (moderate hunger) and our exposure to dietary phytochemicals are also emerging as stresses which are 'good for us' in the same sense. This review focuses on an important extension of this concept: that stress localized within the body (e.g. in a limb) can induce resilience in tissues throughout the body. We describe evidence for the efficacy of two 'remote' protective interventions - remote ischemic conditioning and remote photobiomodulation - and discuss the mechanisms underlying their protective actions. While the biological phenomenon of remote tissue conditioning is only partially understood, it holds promise for protecting critical-to-life tissues while mitigating risks and practical barriers to direct conditioning of these tissues.

Influence of cardiac nerve status on cardiovascular regulation and cardioprotection

Neural elements of the intrinsic cardiac nervous system transduce sensory inputs from the heart, blood vessels and other organs to ensure adequate cardiac function on a beat-to-beat basis. This inter-organ crosstalk is critical for normal function of the heart and other organs; derangements within the nervous system hierarchy contribute to pathogenesis of organ dysfunction. The role of intact cardiac nerves in development of, as well as protection against, ischemic injury is of current interest since it may involve recruitment of intrinsic cardiac ganglia. For instance, ischemic conditioning, a novel protection strategy against organ injury, and in particular remote conditioning, is likely mediated by activation of neural pathways or by endogenous cytoprotective blood-borne substances that stimulate different signalling pathways. This discovery reinforces the concept that inter-organ communication, and maintenance thereof, is key. As such, greater understanding of mechanisms and elucidation of treatment strategies is imperative to improve clinical outcomes particularly in patients with comorbidities. For instance, autonomic imbalance between sympathetic and parasympathetic nervous system regulation can initiate cardiovascular autonomic neuropathy that compromises cardiac stability and function. Neuromodulation therapies that directly target the intrinsic cardiac nervous system or other elements of the nervous system hierarchy are currently being investigated for treatment of different maladies in animal and human studies.

[Skeletal muscle ischemia-reperfusion and ischemic conditioning pathophysiology-clinical applications for the vascular surgeon]

Ischemia-reperfusion, which is characterized by deficient oxygen supply and subsequent restoration of blood flow, can cause irreversible damage to tissue. The vascular surgeon is daily faced with ischemia-reperfusion situations. Indeed, arterial clamping induces ischemia, followed by reperfusion when declamping. Mechanisms underlying ischemia-reperfusion injury are complex and multifactorial. Increases in cellular calcium and reactive oxygen species, initiated during ischemia and then amplified upon reperfusion are thought to be the main mediators of reperfusion injury. Mitochondrial dysfunction also plays an important role. Extensive research has focused on increasing skeletal muscle tolerance to ischemia-reperfusion injury, especially through the use of ischemic conditioning strategies. The purpose of this review is to focus on the cellular responses associated with ischemia-reperfusion, as well as to discuss the effects of ischemic conditioning strategies. This would help the vascular surgeon in daily practice, in order to try to improve surgical outcome in the setting of ischemia-reperfusion.

Ischemic Gastric Conditioning by Preoperative Arterial Embolization Before Oncologic Esophagectomy: A Single-Center Experience

PURPOSE

Surgical esophagectomy is the gold standard treatment of early-stage esophageal cancer. The procedure is complicated with significant morbidity; the most severe complication being the anastomotic leakage. Anastomotic fistulas are reported in 5-25% of cases and are mainly due to gastric transplant ischemia. Here, we report our experience of ischemic pre-conditioning using preoperative arterial embolization (PreopAE) before esophagectomy.

MATERIALS AND METHODS

The medical records of all patients who underwent oncologic esophagectomy from 2008 to 2015 were retrospectively reviewed. Patients were divided into two groups: patients who received PreopAE, and a control group of patients who did not benefit from ischemic pre-conditioning. The target arteries selected for PreopAE were the splenic artery, left gastric artery, and right gastric artery. Evaluation of the results was based on anastomotic leakage, postoperative mortality, technical success of PreopAE, and complications related to the embolization procedure.

RESULTS

Forty-six patients underwent oncologic esophagectomy with PreopAE and 13 patients did not receive ischemic conditioning before surgery. Thirty-eight PreopAE were successfully performed (83%), but right gastric artery embolization failed for 8 patients. Anastomotic leakage occurred in 6 PreopAE patients (13%) and in 6 patients (46%) in the control group (p = 0.02). The mortality rate was 2% in the PreopAE group and 23% in the control group (p = 0.03). Eighteen patients suffered from partial splenic infarction after PreopAE, all treated conservatively.

CONCLUSION

Preoperative ischemic conditioning by arterial embolization before oncologic esophagectomy seems to be effective in preventing anastomotic leakage.

Cardioprotection for percutaneous coronary intervention--reperfusion quality as well as quantity

Ischaemia-reperfusion (IR) injury is an important cause of myocardial damage during percutaneous coronary intervention (PCI). There are few therapies in widespread clinical use which impact on IR injury and it remains an important and underutilized target for treatment in acute myocardial infarction. This review will examine the translational scientific evidence for ischaemic conditioning and pharmacological agents including conditioning mimetics such as cyclosporine, anti-inflammatory agents, and those which modify myocardial glucose metabolism. We will address the reasons why many trials have failed to demonstrate clinical benefit and emphasize the need to deliver the right therapy to the right patient, at the right time to achieve successful translation of cardioprotection from bench-to-bedside. We critique trial design and offer advice for future translational trials in the field to ensure that effective treatments can be demonstrated clinically to improve patient outcomes during PCI.

Stromal derived factor 1α: a chemokine that delivers a two-pronged defence of the myocardium

Alleviating myocardial injury associated with ST elevation myocardial infarction is central to improving the global burden of coronary heart disease. The chemokine stromal cell-derived factor 1α (SDF-1α) has dual potential benefit in this regard. Firstly, SDF-1α is up-regulated in experimental and clinical studies of acute myocardial infarction (AMI) and regulates stem cell migration to sites of injury. SDF-1α delivery to the myocardium after AMI is associated with improved stem cell homing, angiogenesis, and left ventricular function in animal models, and improvements in heart failure and quality of life in humans. Secondly, SDF-1α may have a role in remote ischaemic conditioning (RIC), the phenomenon whereby non-lethal ischaemia–reperfusion applied to an organ or tissue remote from the heart protects the myocardium from lethal ischaemia–reperfusion injury (IRI). SDF-1α is increased in the serum of rats subjected to RIC and protects against myocardial IRI in ex vivo studies. Despite these potential pleiotropic effects, a limitation of SDF-1α is its short plasma half-life due to cleavage by dipeptidyl peptidase-4 (DPP-4). However, DPP-4 inhibitors increase the half-life of SDF-1α by preventing its degradation and are also protective against lethal IRI. In summary, SDF-1 potentially delivers a ‘two-pronged’ defence of the myocardium: acutely protecting it from IRI while simultaneously stimulating repair by recruiting stem cells to the site of injury. In this article we examine the evidence for acute and chronic cardioprotective roles of SDF-1α and discuss potential therapeutic manipulations of this mechanism with DPP-4 inhibitors to protect against lethal tissue injury in the clinical setting.